draft-ietf-lake-edhoc-07.txt   draft-ietf-lake-edhoc-08.txt 
Network Working Group G. Selander Network Working Group G. Selander
Internet-Draft J. Mattsson Internet-Draft J. Mattsson
Intended status: Standards Track F. Palombini Intended status: Standards Track F. Palombini
Expires: 25 November 2021 Ericsson AB Expires: January 13, 2022 Ericsson AB
24 May 2021 July 12, 2021
Ephemeral Diffie-Hellman Over COSE (EDHOC) Ephemeral Diffie-Hellman Over COSE (EDHOC)
draft-ietf-lake-edhoc-07 draft-ietf-lake-edhoc-08
Abstract Abstract
This document specifies Ephemeral Diffie-Hellman Over COSE (EDHOC), a This document specifies Ephemeral Diffie-Hellman Over COSE (EDHOC), a
very compact and lightweight authenticated Diffie-Hellman key very compact and lightweight authenticated Diffie-Hellman key
exchange with ephemeral keys. EDHOC provides mutual authentication, exchange with ephemeral keys. EDHOC provides mutual authentication,
perfect forward secrecy, and identity protection. EDHOC is intended perfect forward secrecy, and identity protection. EDHOC is intended
for usage in constrained scenarios and a main use case is to for usage in constrained scenarios and a main use case is to
establish an OSCORE security context. By reusing COSE for establish an OSCORE security context. By reusing COSE for
cryptography, CBOR for encoding, and CoAP for transport, the cryptography, CBOR for encoding, and CoAP for transport, the
skipping to change at page 1, line 38 skipping to change at page 1, line 38
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Use of EDHOC . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Use of EDHOC . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Message Size Examples . . . . . . . . . . . . . . . . . . 6 1.3. Message Size Examples . . . . . . . . . . . . . . . . . . 5
1.4. Document Structure . . . . . . . . . . . . . . . . . . . 6 1.4. Document Structure . . . . . . . . . . . . . . . . . . . 6
1.5. Terminology and Requirements Language . . . . . . . . . . 6 1.5. Terminology and Requirements Language . . . . . . . . . . 6
2. EDHOC Outline . . . . . . . . . . . . . . . . . . . . . . . . 7 2. EDHOC Outline . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Protocol Elements . . . . . . . . . . . . . . . . . . . . . . 9 3. Protocol Elements . . . . . . . . . . . . . . . . . . . . . . 8
3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. Method and Correlation . . . . . . . . . . . . . . . . . 10 3.2. Method . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2.1. Method . . . . . . . . . . . . . . . . . . . . . . . 10 3.3. Connection Identifiers . . . . . . . . . . . . . . . . . 9
3.2.2. Connection Identifiers . . . . . . . . . . . . . . . 10 3.4. Transport . . . . . . . . . . . . . . . . . . . . . . . . 11
3.2.3. Transport . . . . . . . . . . . . . . . . . . . . . . 11 3.5. Authentication Parameters . . . . . . . . . . . . . . . . 11
3.2.4. Message Correlation . . . . . . . . . . . . . . . . . 11 3.6. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . 16
3.3. Authentication Parameters . . . . . . . . . . . . . . . . 11 3.7. Ephemeral Public Keys . . . . . . . . . . . . . . . . . . 18
3.3.1. Authentication Keys . . . . . . . . . . . . . . . . . 11 3.8. External Authorization Data . . . . . . . . . . . . . . . 18
3.3.2. Identities . . . . . . . . . . . . . . . . . . . . . 12 3.9. Applicability Statement . . . . . . . . . . . . . . . . . 19
3.3.3. Authentication Credentials . . . . . . . . . . . . . 13 4. Key Derivation . . . . . . . . . . . . . . . . . . . . . . . 21
3.3.4. Identification of Credentials . . . . . . . . . . . . 15
3.4. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . 16
3.5. Ephemeral Public Keys . . . . . . . . . . . . . . . . . . 18
3.6. External Authorization Data . . . . . . . . . . . . . . . 18
3.7. Applicability Statement . . . . . . . . . . . . . . . . . 19
4. Key Derivation . . . . . . . . . . . . . . . . . . . . . . . 20
4.1. EDHOC-Exporter Interface . . . . . . . . . . . . . . . . 23 4.1. EDHOC-Exporter Interface . . . . . . . . . . . . . . . . 23
5. Message Formatting and Processing . . . . . . . . . . . . . . 23 5. Message Formatting and Processing . . . . . . . . . . . . . . 24
5.1. Encoding of bstr_identifier . . . . . . . . . . . . . . . 24 5.1. Message Processing Outline . . . . . . . . . . . . . . . 24
5.2. Message Processing Outline . . . . . . . . . . . . . . . 24 5.2. EDHOC Message 1 . . . . . . . . . . . . . . . . . . . . . 25
5.3. EDHOC Message 1 . . . . . . . . . . . . . . . . . . . . . 25 5.3. EDHOC Message 2 . . . . . . . . . . . . . . . . . . . . . 27
5.3.1. Formatting of Message 1 . . . . . . . . . . . . . . . 25 5.4. EDHOC Message 3 . . . . . . . . . . . . . . . . . . . . . 30
5.3.2. Initiator Processing of Message 1 . . . . . . . . . . 26 5.5. EDHOC Message 4 . . . . . . . . . . . . . . . . . . . . . 33
5.3.3. Responder Processing of Message 1 . . . . . . . . . . 27 6. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 35
5.4. EDHOC Message 2 . . . . . . . . . . . . . . . . . . . . . 28
5.4.1. Formatting of Message 2 . . . . . . . . . . . . . . . 28
5.4.2. Responder Processing of Message 2 . . . . . . . . . . 28
5.4.3. Initiator Processing of Message 2 . . . . . . . . . . 30
5.5. EDHOC Message 3 . . . . . . . . . . . . . . . . . . . . . 31
5.5.1. Formatting of Message 3 . . . . . . . . . . . . . . . 31
5.5.2. Initiator Processing of Message 3 . . . . . . . . . . 31
5.5.3. Responder Processing of Message 3 . . . . . . . . . . 34
6. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 34
6.1. Success . . . . . . . . . . . . . . . . . . . . . . . . . 36 6.1. Success . . . . . . . . . . . . . . . . . . . . . . . . . 36
6.2. Unspecified . . . . . . . . . . . . . . . . . . . . . . . 36 6.2. Unspecified . . . . . . . . . . . . . . . . . . . . . . . 36
6.3. Wrong Selected Cipher Suite . . . . . . . . . . . . . . . 36 6.3. Wrong Selected Cipher Suite . . . . . . . . . . . . . . . 36
6.3.1. Cipher Suite Negotiation . . . . . . . . . . . . . . 37 7. Security Considerations . . . . . . . . . . . . . . . . . . . 38
6.3.2. Examples . . . . . . . . . . . . . . . . . . . . . . 37 7.1. Security Properties . . . . . . . . . . . . . . . . . . . 38
7. Transferring EDHOC and Deriving an OSCORE Context . . . . . . 38 7.2. Cryptographic Considerations . . . . . . . . . . . . . . 40
7.1. EDHOC Message 4 . . . . . . . . . . . . . . . . . . . . . 38 7.3. Cipher Suites and Cryptographic Algorithms . . . . . . . 41
7.1.1. Formatting of Message 4 . . . . . . . . . . . . . . . 39 7.4. Unprotected Data . . . . . . . . . . . . . . . . . . . . 42
7.1.2. Responder Processing of Message 4 . . . . . . . . . . 39 7.5. Denial-of-Service . . . . . . . . . . . . . . . . . . . . 42
7.1.3. Initiator Processing of Message 4 . . . . . . . . . . 40 7.6. Implementation Considerations . . . . . . . . . . . . . . 43
7.2. Transferring EDHOC in CoAP . . . . . . . . . . . . . . . 40 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 44
8. Security Considerations . . . . . . . . . . . . . . . . . . . 42 8.1. EDHOC Exporter Label . . . . . . . . . . . . . . . . . . 44
8.1. Security Properties . . . . . . . . . . . . . . . . . . . 42 8.2. EDHOC Cipher Suites Registry . . . . . . . . . . . . . . 45
8.2. Cryptographic Considerations . . . . . . . . . . . . . . 45 8.3. EDHOC Method Type Registry . . . . . . . . . . . . . . . 47
8.3. Cipher Suites and Cryptographic Algorithms . . . . . . . 46 8.4. EDHOC Error Codes Registry . . . . . . . . . . . . . . . 47
8.4. Unprotected Data . . . . . . . . . . . . . . . . . . . . 46 8.5. COSE Header Parameters Registry . . . . . . . . . . . . . 47
8.5. Denial-of-Service . . . . . . . . . . . . . . . . . . . . 47 8.6. COSE Header Parameters Registry . . . . . . . . . . . . . 47
8.6. Implementation Considerations . . . . . . . . . . . . . . 47 8.7. COSE Key Common Parameters Registry . . . . . . . . . . . 48
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49 8.8. The Well-Known URI Registry . . . . . . . . . . . . . . . 48
9.1. EDHOC Exporter Label . . . . . . . . . . . . . . . . . . 49 8.9. Media Types Registry . . . . . . . . . . . . . . . . . . 48
9.2. EDHOC Cipher Suites Registry . . . . . . . . . . . . . . 49 8.10. CoAP Content-Formats Registry . . . . . . . . . . . . . . 49
9.3. EDHOC Method Type Registry . . . . . . . . . . . . . . . 50 8.11. EDHOC External Authorization Data . . . . . . . . . . . . 49
9.4. EDHOC Error Codes Registry . . . . . . . . . . . . . . . 51 8.12. Expert Review Instructions . . . . . . . . . . . . . . . 50
9.5. The Well-Known URI Registry . . . . . . . . . . . . . . . 51 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 50
9.6. Media Types Registry . . . . . . . . . . . . . . . . . . 51 9.1. Normative References . . . . . . . . . . . . . . . . . . 50
9.7. CoAP Content-Formats Registry . . . . . . . . . . . . . . 52 9.2. Informative References . . . . . . . . . . . . . . . . . 53
9.8. Expert Review Instructions . . . . . . . . . . . . . . . 52 Appendix A. Use with OSCORE and Transfer over CoAP . . . . . . . 55
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 53 A.1. Selecting EDHOC Connection Identifier . . . . . . . . . . 55
10.1. Normative References . . . . . . . . . . . . . . . . . . 53 A.2. Deriving the OSCORE Security Context . . . . . . . . . . 56
10.2. Informative References . . . . . . . . . . . . . . . . . 55 A.3. Transferring EDHOC over CoAP . . . . . . . . . . . . . . 57
Appendix A. Compact Representation . . . . . . . . . . . . . . . 58 Appendix B. Compact Representation . . . . . . . . . . . . . . . 60
Appendix B. Use of CBOR, CDDL and COSE in EDHOC . . . . . . . . 58 Appendix C. Use of CBOR, CDDL and COSE in EDHOC . . . . . . . . 60
B.1. CBOR and CDDL . . . . . . . . . . . . . . . . . . . . . . 59 C.1. CBOR and CDDL . . . . . . . . . . . . . . . . . . . . . . 60
B.2. CDDL Definitions . . . . . . . . . . . . . . . . . . . . 59 C.2. CDDL Definitions . . . . . . . . . . . . . . . . . . . . 61
B.3. COSE . . . . . . . . . . . . . . . . . . . . . . . . . . 61 C.3. COSE . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Appendix C. Test Vectors . . . . . . . . . . . . . . . . . . . . 61 Appendix D. Test Vectors . . . . . . . . . . . . . . . . . . . . 63
C.1. Test Vectors for EDHOC Authenticated with Signature Keys D.1. Test Vectors for EDHOC Authenticated with Signature Keys
(x5t) . . . . . . . . . . . . . . . . . . . . . . . . . . 62 (x5t) . . . . . . . . . . . . . . . . . . . . . . . . . . 63
C.1.1. Message_1 . . . . . . . . . . . . . . . . . . . . . . 62 D.2. Test Vectors for EDHOC Authenticated with Static Diffie-
C.1.2. Message_2 . . . . . . . . . . . . . . . . . . . . . . 63 Hellman Keys . . . . . . . . . . . . . . . . . . . . . . 81
C.1.3. Message_3 . . . . . . . . . . . . . . . . . . . . . . 71 Appendix E. Applicability Template . . . . . . . . . . . . . . . 96
C.1.4. OSCORE Security Context Derivation . . . . . . . . . 77 Appendix F. EDHOC Message Deduplication . . . . . . . . . . . . 96
C.2. Test Vectors for EDHOC Authenticated with Static Appendix G. Transports Not Natively Providing Correlation . . . 97
Diffie-Hellman Keys . . . . . . . . . . . . . . . . . . . 79 Appendix H. Change Log . . . . . . . . . . . . . . . . . . . . . 98
C.2.1. Message_1 . . . . . . . . . . . . . . . . . . . . . . 80 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 101
C.2.2. Message_2 . . . . . . . . . . . . . . . . . . . . . . 81 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 101
C.2.3. Message_3 . . . . . . . . . . . . . . . . . . . . . . 87
C.2.4. OSCORE Security Context Derivation . . . . . . . . . 92
Appendix D. Applicability Template . . . . . . . . . . . . . . . 94
Appendix E. EDHOC Message Deduplication . . . . . . . . . . . . 95
Appendix F. Change Log . . . . . . . . . . . . . . . . . . . . . 96
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 99
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 99
1. Introduction 1. Introduction
1.1. Motivation 1.1. Motivation
Many Internet of Things (IoT) deployments require technologies which Many Internet of Things (IoT) deployments require technologies which
are highly performant in constrained environments [RFC7228]. IoT are highly performant in constrained environments [RFC7228]. IoT
devices may be constrained in various ways, including memory, devices may be constrained in various ways, including memory,
storage, processing capacity, and power. The connectivity for these storage, processing capacity, and power. The connectivity for these
settings may also exhibit constraints such as unreliable and lossy settings may also exhibit constraints such as unreliable and lossy
skipping to change at page 5, line 40 skipping to change at page 5, line 18
actuators. actuators.
A typical setting is when one of the endpoints is constrained or in a A typical setting is when one of the endpoints is constrained or in a
constrained network, and the other endpoint is a node on the Internet constrained network, and the other endpoint is a node on the Internet
(such as a mobile phone) or at the edge of the constrained network (such as a mobile phone) or at the edge of the constrained network
(such as a gateway). Thing-to-thing interactions over constrained (such as a gateway). Thing-to-thing interactions over constrained
networks are also relevant since both endpoints would then benefit networks are also relevant since both endpoints would then benefit
from the lightweight properties of the protocol. EDHOC could e.g. be from the lightweight properties of the protocol. EDHOC could e.g. be
run when a device connects for the first time, or to establish fresh run when a device connects for the first time, or to establish fresh
keys which are not revealed by a later compromise of the long-term keys which are not revealed by a later compromise of the long-term
keys. Further security properties are described in Section 8.1. keys. Further security properties are described in Section 7.1.
EDHOC enables the reuse of the same lightweight primitives as OSCORE: EDHOC enables the reuse of the same lightweight primitives as OSCORE:
CBOR for encoding, COSE for cryptography, and CoAP for transport. By CBOR for encoding, COSE for cryptography, and CoAP for transport. By
reusing existing libraries the additional code size can be kept very reusing existing libraries the additional code size can be kept very
low. Note that, while CBOR and COSE primitives are built into the low. Note that, while CBOR and COSE primitives are built into the
protocol messages, EDHOC is not bound to a particular transport. protocol messages, EDHOC is not bound to a particular transport.
However, it is recommended to transfer EDHOC messages in CoAP However, it is recommended to transfer EDHOC messages in CoAP
payloads as is detailed in Section 7.2. payloads as is detailed in Appendix A.3.
1.3. Message Size Examples 1.3. Message Size Examples
Compared to the DTLS 1.3 handshake [I-D.ietf-tls-dtls13] with ECDHE Compared to the DTLS 1.3 handshake [I-D.ietf-tls-dtls13] with ECDHE
and connection ID, the number of bytes in EDHOC + CoAP can be less and connection ID, the number of bytes in EDHOC + CoAP can be less
than 1/6 when RPK authentication is used, see than 1/6 when RPK authentication is used, see
[I-D.ietf-lwig-security-protocol-comparison]. Figure 1 shows two [I-D.ietf-lwig-security-protocol-comparison]. Figure 1 shows two
examples of message sizes for EDHOC with different kinds of examples of message sizes for EDHOC with different kinds of
authentication keys and different COSE header parameters for authentication keys and different COSE header parameters for
identification: static Diffie-Hellman keys identified by 'kid' identification: static Diffie-Hellman keys identified by 'kid'
[I-D.ietf-cose-rfc8152bis-struct], and X.509 signature certificates [I-D.ietf-cose-rfc8152bis-struct], and X.509 signature certificates
identified by a hash value using 'x5t' [I-D.ietf-cose-x509]. identified by a hash value using 'x5t' [I-D.ietf-cose-x509].
================================= =================================
kid x5t kid x5t
--------------------------------- ---------------------------------
message_1 37 37 message_1 37 37
message_2 46 117 message_2 45 116
message_3 20 91 message_3 20 91
--------------------------------- ---------------------------------
Total 103 245 Total 103 245
================================= =================================
Figure 1: Example of message sizes in bytes. Figure 1: Example of message sizes in bytes.
1.4. Document Structure 1.4. Document Structure
The remainder of the document is organized as follows: Section 2 The remainder of the document is organized as follows: Section 2
outlines EDHOC authenticated with digital signatures, Section 3 outlines EDHOC authenticated with digital signatures, Section 3
describes the protocol elements of EDHOC, including message flow, and describes the protocol elements of EDHOC, including message flow, and
formatting of the ephemeral public keys, Section 4 describes the key formatting of the ephemeral public keys, Section 4 describes the key
derivation, Section 5 specifies EDHOC with authentication based on derivation, Section 5 specifies EDHOC with authentication based on
signature keys or static Diffie-Hellman keys, Section 6 specifies the signature keys or static Diffie-Hellman keys, Section 6 specifies the
EDHOC error message, and Section 7 describes how EDHOC can be EDHOC error message, and Appendix A describes how EDHOC can be
transferred in CoAP and used to establish an OSCORE security context. transferred in CoAP and used to establish an OSCORE security context.
1.5. Terminology and Requirements Language 1.5. Terminology and Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
Readers are expected to be familiar with the terms and concepts Readers are expected to be familiar with the terms and concepts
described in CBOR [RFC8949], CBOR Sequences [RFC8742], COSE described in CBOR [RFC8949], CBOR Sequences [RFC8742], COSE
structures and process [I-D.ietf-cose-rfc8152bis-struct], COSE structures and process [I-D.ietf-cose-rfc8152bis-struct], COSE
algorithms [I-D.ietf-cose-rfc8152bis-algs], and CDDL [RFC8610]. The algorithms [I-D.ietf-cose-rfc8152bis-algs], and CDDL [RFC8610]. The
Concise Data Definition Language (CDDL) is used to express CBOR data Concise Data Definition Language (CDDL) is used to express CBOR data
structures [RFC8949]. Examples of CBOR and CDDL are provided in structures [RFC8949]. Examples of CBOR and CDDL are provided in
Appendix B.1. When referring to CBOR, this specification always Appendix C.1. When referring to CBOR, this specification always
refer to Deterministically Encoded CBOR as specified in Sections refer to Deterministically Encoded CBOR as specified in Sections
4.2.1 and 4.2.2 of [RFC8949]. 4.2.1 and 4.2.2 of [RFC8949].
The single output from authenticated encryption (including the The single output from authenticated encryption (including the
authentication tag) is called 'ciphertext', following [RFC5116]. authentication tag) is called 'ciphertext', following [RFC5116].
2. EDHOC Outline 2. EDHOC Outline
EDHOC specifies different authentication methods of the Diffie- EDHOC specifies different authentication methods of the Diffie-
Hellman key exchange: digital signatures and static Diffie-Hellman Hellman key exchange: digital signatures and static Diffie-Hellman
skipping to change at page 7, line 47 skipping to change at page 7, line 23
+-------------------------------------------------------->| +-------------------------------------------------------->|
| | | |
Figure 2: Authenticated encryption variant of the SIGMA-I protocol. Figure 2: Authenticated encryption variant of the SIGMA-I protocol.
The parties exchanging messages are called Initiator (I) and The parties exchanging messages are called Initiator (I) and
Responder (R). They exchange ephemeral public keys, compute a shared Responder (R). They exchange ephemeral public keys, compute a shared
secret, and derive symmetric application keys used to protect secret, and derive symmetric application keys used to protect
application data. application data.
* G_X and G_Y are the ECDH ephemeral public keys of I and R, o G_X and G_Y are the ECDH ephemeral public keys of I and R,
respectively. respectively.
* CRED_I and CRED_R are the credentials containing the public o CRED_I and CRED_R are the credentials containing the public
authentication keys of I and R, respectively. authentication keys of I and R, respectively.
* ID_CRED_I and ID_CRED_R are credential identifiers enabling the o ID_CRED_I and ID_CRED_R are credential identifiers enabling the
recipient party to retrieve the credential of I and R, recipient party to retrieve the credential of I and R,
respectively. respectively.
* Sig(I; . ) and Sig(R; . ) denote signatures made with the private o Sig(I; . ) and Sig(R; . ) denote signatures made with the private
authentication key of I and R, respectively. authentication key of I and R, respectively.
* AEAD(K; . ) denotes authenticated encryption with additional data o AEAD(K; . ) denotes authenticated encryption with additional data
using a key K derived from the shared secret. using a key K derived from the shared secret.
In order to create a "full-fledged" protocol some additional protocol In order to create a "full-fledged" protocol some additional protocol
elements are needed. EDHOC adds: elements are needed. EDHOC adds:
* Explicit connection identifiers C_I, C_R chosen by I and R, o Transcript hashes (hashes of message data) TH_2, TH_3, TH_4 used
respectively, enabling the recipient to find the protocol state.
* Transcript hashes (hashes of message data) TH_2, TH_3, TH_4 used
for key derivation and as additional authenticated data. for key derivation and as additional authenticated data.
* Computationally independent keys derived from the ECDH shared o Computationally independent keys derived from the ECDH shared
secret and used for authenticated encryption of different secret and used for authenticated encryption of different
messages. messages.
* An optional fourth message giving explicit key confirmation to I o An optional fourth message giving explicit key confirmation to I
in deployments where no protected application data is sent from R in deployments where no protected application data is sent from R
to I. to I.
* A key material exporter and a key update function enabling o A key material exporter and a key update function enabling
frequent forward secrecy. frequent forward secrecy.
* Verification of a common preferred cipher suite: o Verification of a common preferred cipher suite:
- The Initiator lists supported cipher suites in order of * The Initiator lists supported cipher suites in order of
preference preference
- The Responder verifies that the selected cipher suite is the * The Responder verifies that the selected cipher suite is the
first supported cipher suite (or else rejects and states first supported cipher suite (or else rejects and states
supported cipher suites). supported cipher suites).
* Method types and error handling. o Method types and error handling.
* Transport of external authorization data. o Selection of connection identifiers C_I and C_R which may be used
to identify established keys or protocol state.
o Transport of external authorization data.
EDHOC is designed to encrypt and integrity protect as much EDHOC is designed to encrypt and integrity protect as much
information as possible, and all symmetric keys are derived using as information as possible, and all symmetric keys are derived using as
much previous information as possible. EDHOC is furthermore designed much previous information as possible. EDHOC is furthermore designed
to be as compact and lightweight as possible, in terms of message to be as compact and lightweight as possible, in terms of message
sizes, processing, and the ability to reuse already existing CBOR, sizes, processing, and the ability to reuse already existing CBOR,
COSE, and CoAP libraries. COSE, and CoAP libraries.
To simplify for implementors, the use of CBOR and COSE in EDHOC is To simplify for implementors, the use of CBOR and COSE in EDHOC is
summarized in Appendix B and test vectors including CBOR diagnostic summarized in Appendix C and test vectors including CBOR diagnostic
notation are given in Appendix C. notation are given in Appendix D.
3. Protocol Elements 3. Protocol Elements
3.1. General 3.1. General
An EDHOC message flow consists of three mandatory messages An EDHOC message flow consists of three mandatory messages
(message_1, message_2, message_3) between Initiator and Responder, an (message_1, message_2, message_3) between Initiator and Responder, an
optional fourth message (message_4), plus an EDHOC error message. optional fourth message (message_4), plus an EDHOC error message.
EDHOC messages are CBOR Sequences [RFC8742], see Figure 3. The EDHOC messages are CBOR Sequences [RFC8742], see Figure 3. The
protocol elements in the figure are introduced in the following protocol elements in the figure are introduced in the following
sections. Message formatting and processing is specified in sections. Message formatting and processing is specified in
Section 5 and Section 6. An implementation may support only Section 5 and Section 6. An implementation may support only
Initiator or only Responder. Initiator or only Responder.
Application data is protected using the agreed application algorithms Application data is protected using the agreed application algorithms
(AEAD, hash) in the selected cipher suite (see Section 3.4) and the (AEAD, hash) in the selected cipher suite (see Section 3.6) and the
application can make use of the established connection identifiers application can make use of the established connection identifiers
C_1, C_I, and C_R (see Section 3.2.4). EDHOC may be used with the C_I and C_R (see Section 3.3). EDHOC may be used with the media type
media type application/edhoc defined in Section 9. application/edhoc defined in Section 8.
The Initiator can derive symmetric application keys after creating The Initiator can derive symmetric application keys after creating
EDHOC message_3, see Section 4.1. Application protected data can EDHOC message_3, see Section 4.1. Application protected data can
therefore be sent in parallel or together with EDHOC message_3. therefore be sent in parallel or together with EDHOC message_3.
Initiator Responder Initiator Responder
| C_1, METHOD_CORR, SUITES_I, G_X, C_I, EAD_1 | | METHOD, SUITES_I, G_X, C_I, EAD_1 |
+------------------------------------------------------------------>| +------------------------------------------------------------------>|
| message_1 | | message_1 |
| | | |
| C_I, G_Y, C_R, Enc(ID_CRED_R, Signature_or_MAC_2, EAD_2) | | G_Y, C_R, Enc(ID_CRED_R, Signature_or_MAC_2, EAD_2) |
|<------------------------------------------------------------------+ |<------------------------------------------------------------------+
| message_2 | | message_2 |
| | | |
| C_R, AEAD(K_3ae; ID_CRED_I, Signature_or_MAC_3, EAD_3) | | AEAD(K_3ae; ID_CRED_I, Signature_or_MAC_3, EAD_3) |
+------------------------------------------------------------------>| +------------------------------------------------------------------>|
| message_3 | | message_3 |
Figure 3: EDHOC Message Flow Figure 3: EDHOC Message Flow
3.2. Method and Correlation
The data item METHOD_CORR in message_1 (see Section 5.3.1), is an
integer specifying the method and the correlation properties of the
transport, which are described in this section.
3.2.1. Method 3.2. Method
EDHOC supports authentication with signature or static Diffie-Hellman The data item METHOD in message_1 (see Section 5.2.1), is an integer
keys, as defined in the four authentication methods: 0, 1, 2, and 3, specifying the authentication method. EDHOC supports authentication
see Figure 4. (Method 0 corresponds to the case outlined in with signature or static Diffie-Hellman keys, as defined in the four
Section 2 where both Initiator and Responder authenticate with authentication methods: 0, 1, 2, and 3, see Figure 4. (Method 0
signature keys.) corresponds to the case outlined in Section 2 where both Initiator
and Responder authenticate with signature keys.)
An implementation may support only a single method. The Initiator An implementation may support only a single method. The Initiator
and the Responder need to have agreed on a single method to be used and the Responder need to have agreed on a single method to be used
for EDHOC, see Section 3.7. for EDHOC, see Section 3.9.
+-------+-------------------+-------------------+-------------------+ +-------+-------------------+-------------------+-------------------+
| Value | Initiator | Responder | Reference | | Value | Initiator | Responder | Reference |
+-------+-------------------+-------------------+-------------------+ +-------+-------------------+-------------------+-------------------+
| 0 | Signature Key | Signature Key | [[this document]] | | 0 | Signature Key | Signature Key | [[this document]] |
| 1 | Signature Key | Static DH Key | [[this document]] | | 1 | Signature Key | Static DH Key | [[this document]] |
| 2 | Static DH Key | Signature Key | [[this document]] | | 2 | Static DH Key | Signature Key | [[this document]] |
| 3 | Static DH Key | Static DH Key | [[this document]] | | 3 | Static DH Key | Static DH Key | [[this document]] |
+-------+-------------------+-------------------+-------------------+ +-------+-------------------+-------------------+-------------------+
Figure 4: Method Types Figure 4: Method Types
3.2.2. Connection Identifiers 3.3. Connection Identifiers
EDHOC includes optional connection identifiers (C_1, C_I, C_R). The EDHOC includes the selection of connection identifiers (C_I, C_R)
connection identifiers C_1, C_I, and C_R do not have any identifying a connection for which keys are agreed. Connection
cryptographic purpose in EDHOC. They contain information identifiers may be used in the ongoing EDHOC protocol (see
facilitating retrieval of the protocol state and may therefore be Section 3.3.2) or in a subsequent application protocol, e.g., OSCORE
very short. C_1 is always set to "null", while C_I and C_R are (see Section 3.3.3). The connection identifiers do not have any
chosen by I and R, respectively. One byte connection identifiers are cryptographic purpose in EDHOC.
realistic in many scenarios as most constrained devices only have a
few connections. In cases where a node only has one connection, the
identifiers may even be the empty byte string.
The connection identifier MAY be used with an application protocol Connection identifiers in EDHOC are byte strings or integers, encoded
(e.g. OSCORE) for which EDHOC establishes keys, in which case the in CBOR. One byte connection identifiers (the integers -24 to 23 and
connection identifiers SHALL adhere to the requirements for that the empty bytestring h'') are realistic in many scenarios as most
protocol. Each party choses a connection identifier it desires the constrained devices only have a few connections.
other party to use in outgoing messages. (For OSCORE this results in
the endpoint selecting its Recipient ID, see Section 3.1 of
[RFC8613]).
3.2.3. Transport 3.3.1. Selection of Connection Identifiers
C_I and C_R are chosen by I and R, respectively. The Initiator
selects C_I and sends it in message_1 for the Responder to use as a
reference to the connection in communications with the Initiator.
The Responder selects C_R and sends in message_2 for the Initiator to
use as a reference to the connection in communications with the
Responder.
If connection identifiers are used by an application protocol for
which EDHOC establishes keys then the selected connection identifiers
SHALL adhere to the requirements for that protocol, see Section 3.3.3
for an example.
3.3.2. Use of Connection Identifiers in EDHOC
Connection identifiers may be used to correlate EDHOC messages and
facilitate the retrieval of protocol state during EDHOC protocol
execution. EDHOC transports that do not inherently provide
correlation across all messages of an exchange can send connection
identifiers along with EDHOC messages to gain that required
capability, see Section 3.4. For an example when CoAP is used as
transport, see Appendix A.3.
3.3.3. Use of Connection Identifiers in OSCORE
For OSCORE, the choice of a connection identifier results in the
endpoint selecting its Recipient ID, see Section 3.1 of [RFC8613]),
for which certain uniqueness requirements apply, see Section 3.3 of
[RFC8613]). Therefore the Initiator and the Responder MUST NOT
select connection identifiers such that it results in same OSCORE
Recipient ID. Since the Recipient ID is a byte string and a EDHOC
connection identifier is either a CBOR byte string or a CBOR integer,
care must be taken when selecting the connection identifiers and
converting them to Recipient IDs. A mapping from EDHOC connection
identifier to OSCORE Recipient ID is specified in Appendix A.1.
3.4. Transport
Cryptographically, EDHOC does not put requirements on the lower Cryptographically, EDHOC does not put requirements on the lower
layers. EDHOC is not bound to a particular transport layer, and can layers. EDHOC is not bound to a particular transport layer, and can
be used in environments without IP. The application using EDHOC is even be used in environments without IP. The transport is
responsible to handle message loss, reordering, message duplication, responsible, where necessary, to handle:
fragmentation, demultiplex EDHOC messages from other types of
messages, and denial of service protection, where necessary.
The Initiator and the Responder need to have agreed on a transport to o message loss,
be used for EDHOC, see Section 3.7. It is recommended to transport
EDHOC in CoAP payloads, see Section 7.
3.2.4. Message Correlation o message reordering,
If the whole transport path provides a mechanism for correlating o message duplication,
messages received with messages previously sent, then some of the
connection identifiers may be omitted. There are four cases:
* corr = 0, the transport does not provide a correlation mechanism. o fragmentation,
* corr = 1, the transport provides a correlation mechanism that o demultiplex EDHOC messages from other types of messages, and
enables the Responder to correlate message_2 and message_1 as well
as message_4 and message_3.
* corr = 2, the transport provides a correlation mechanism that o denial of service protection.
enables the Initiator to correlate message_3 and message_2.
* corr = 3, the transport provides a correlation mechanism that Besides these common transport oriented properties, EDHOC transport
enables both parties to correlate all three messages. additionally needs to support the correlation between EDHOC messages,
including an indication of a message being message_1. The
correlation may reuse existing mechanisms in the transport protocol.
For example, the CoAP Token may be used to correlate EDHOC messages
in a CoAP response and an associated CoAP request. In the absense of
correlation between a message received and a message previously sent
inherent to the transport, the EDHOC connection identifiers may be
added, e.g. by prepending the appropriate connection identifier (when
available from the EDHOC protocol) to the EDHOC message. Transport
of EDHOC in CoAP payloads is described in Appendix A.3, which also
shows how to use connection identifiers and message_1 indication with
CoAP.
For example, if the key exchange is transported over CoAP, the CoAP The Initiator and the Responder need to have agreed on a transport to
Token can be used to correlate messages, see Section 7.2. be used for EDHOC, see Section 3.9.
3.3. Authentication Parameters 3.5. Authentication Parameters
3.3.1. Authentication Keys 3.5.1. Authentication Keys
The authentication key MUST be a signature key or static Diffie- The authentication key MUST be a signature key or static Diffie-
Hellman key. The Initiator and the Responder MAY use different types Hellman key. The Initiator and the Responder MAY use different types
of authentication keys, e.g. one uses a signature key and the other of authentication keys, e.g. one uses a signature key and the other
uses a static Diffie-Hellman key. When using a signature key, the uses a static Diffie-Hellman key. When using a signature key, the
authentication is provided by a signature. When using a static authentication is provided by a signature. When using a static
Diffie-Hellman key the authentication is provided by a Message Diffie-Hellman key the authentication is provided by a Message
Authentication Code (MAC) computed from an ephemeral-static ECDH Authentication Code (MAC) computed from an ephemeral-static ECDH
shared secret which enables significant reductions in message sizes. shared secret which enables significant reductions in message sizes.
The MAC is implemented with an AEAD algorithm. When using static The MAC is implemented with an AEAD algorithm. When using static
Diffie-Hellman keys the Initiator's and Responder's private Diffie-Hellman keys the Initiator's and Responder's private
authentication keys are called I and R, respectively, and the public authentication keys are called I and R, respectively, and the public
authentication keys are called G_I and G_R, respectively. The authentication keys are called G_I and G_R, respectively. The
authentication key algorithm needs to specified with enough authentication key algorithm needs to specified with enough
parameters to make it completely determined. Note that for most parameters to make it completely determined. Note that for most
signature algorithms, the signature is determined by the signature signature algorithms, the signature is determined by the signature
algorithm and the authentication key algorithm together. For algorithm and the authentication key algorithm together. For
example, the curve used in the signature is typically determined by example, the curve used in the signature is typically determined by
the authentication key parameters. the authentication key parameters.
skipping to change at page 12, line 13 skipping to change at page 12, line 16
Diffie-Hellman keys the Initiator's and Responder's private Diffie-Hellman keys the Initiator's and Responder's private
authentication keys are called I and R, respectively, and the public authentication keys are called I and R, respectively, and the public
authentication keys are called G_I and G_R, respectively. The authentication keys are called G_I and G_R, respectively. The
authentication key algorithm needs to specified with enough authentication key algorithm needs to specified with enough
parameters to make it completely determined. Note that for most parameters to make it completely determined. Note that for most
signature algorithms, the signature is determined by the signature signature algorithms, the signature is determined by the signature
algorithm and the authentication key algorithm together. For algorithm and the authentication key algorithm together. For
example, the curve used in the signature is typically determined by example, the curve used in the signature is typically determined by
the authentication key parameters. the authentication key parameters.
* Only the Responder SHALL have access to the Responder's private o Only the Responder SHALL have access to the Responder's private
authentication key. authentication key.
* Only the Initiator SHALL have access to the Initiator's private o Only the Initiator SHALL have access to the Initiator's private
authentication key. authentication key.
3.3.2. Identities 3.5.2. Identities
EDHOC assumes the existence of mechanisms (certification authority, EDHOC assumes the existence of mechanisms (certification authority,
trusted third party, manual distribution, etc.) for specifying and trusted third party, manual distribution, etc.) for specifying and
distributing authentication keys and identities. Policies are set distributing authentication keys and identities. Policies are set
based on the identity of the other party, and parties typically only based on the identity of the other party, and parties typically only
allow connections from a specific identity or a small restricted set allow connections from a specific identity or a small restricted set
of identities. For example, in the case of a device connecting to a of identities. For example, in the case of a device connecting to a
network, the network may only allow connections from devices which network, the network may only allow connections from devices which
authenticate with certificates having a particular range of serial authenticate with certificates having a particular range of serial
numbers in the subject field and signed by a particular CA. On the numbers in the subject field and signed by a particular CA. On the
other side, the device may only be allowed to connect to a network other side, the device may only be allowed to connect to a network
which authenticates with a particular public key (information of which authenticates with a particular public key (information of
which may be provisioned, e.g., out of band or in the external which may be provisioned, e.g., out of band or in the external
authorization data, see Section 3.6). authorization data, see Section 3.8).
The EDHOC implementation must be able to receive and enforce The EDHOC implementation must be able to receive and enforce
information from the application about what is the intended endpoint, information from the application about what is the intended endpoint,
and in particular whether it is a specific identity or a set of and in particular whether it is a specific identity or a set of
identities. identities.
* When a Public Key Infrastructure (PKI) is used, the trust anchor o When a Public Key Infrastructure (PKI) is used, the trust anchor
is a Certification Authority (CA) certificate, and the identity is is a Certification Authority (CA) certificate, and the identity is
the subject whose unique name (e.g. a domain name, NAI, or EUI) is the subject whose unique name (e.g. a domain name, NAI, or EUI) is
included in the endpoint's certificate. Before running EDHOC each included in the endpoint's certificate. Before running EDHOC each
party needs at least one CA public key certificate, or just the party needs at least one CA public key certificate, or just the
public key, and a specific identity or set of identities it is public key, and a specific identity or set of identities it is
allowed to communicate with. Only validated public-key allowed to communicate with. Only validated public-key
certificates with an allowed subject name, as specified by the certificates with an allowed subject name, as specified by the
application, are to be accepted. EDHOC provides proof that the application, are to be accepted. EDHOC provides proof that the
other party possesses the private authentication key corresponding other party possesses the private authentication key corresponding
to the public authentication key in its certificate. The to the public authentication key in its certificate. The
certification path provides proof that the subject of the certification path provides proof that the subject of the
certificate owns the public key in the certificate. certificate owns the public key in the certificate.
* When public keys are used but not with a PKI (RPK, self-signed o When public keys are used but not with a PKI (RPK, self-signed
certificate), the trust anchor is the public authentication key of certificate), the trust anchor is the public authentication key of
the other party. In this case, the identity is typically directly the other party. In this case, the identity is typically directly
associated to the public authentication key of the other party. associated to the public authentication key of the other party.
For example, the name of the subject may be a canonical For example, the name of the subject may be a canonical
representation of the public key. Alternatively, if identities representation of the public key. Alternatively, if identities
can be expressed in the form of unique subject names assigned to can be expressed in the form of unique subject names assigned to
public keys, then a binding to identity can be achieved by public keys, then a binding to identity can be achieved by
including both public key and associated subject name in the including both public key and associated subject name in the
protocol message computation: CRED_I or CRED_R may be a self- protocol message computation: CRED_I or CRED_R may be a self-
signed certificate or COSE_Key containing the public signed certificate or COSE_Key containing the public
authentication key and the subject name, see Section 3.3.3. authentication key and the subject name, see Section 3.5.3.
Before running EDHOC, each endpoint needs a specific public Before running EDHOC, each endpoint needs a specific public
authentication key/unique associated subject name, or a set of authentication key/unique associated subject name, or a set of
public authentication keys/unique associated subject names, which public authentication keys/unique associated subject names, which
it is allowed to communicate with. EDHOC provides proof that the it is allowed to communicate with. EDHOC provides proof that the
other party possesses the private authentication key corresponding other party possesses the private authentication key corresponding
to the public authentication key. to the public authentication key.
3.3.3. Authentication Credentials 3.5.3. Authentication Credentials
The authentication credentials, CRED_I and CRED_R, contain the public The authentication credentials, CRED_I and CRED_R, contain the public
authentication key of the Initiator and the Responder, respectively. authentication key of the Initiator and the Responder, respectively.
The Initiator and the Responder MAY use different types of The Initiator and the Responder MAY use different types of
credentials, e.g. one uses an RPK and the other uses a public key credentials, e.g. one uses an RPK and the other uses a public key
certificate. certificate.
The credentials CRED_I and CRED_R are signed or MAC:ed (depending on The credentials CRED_I and CRED_R are signed or MAC:ed (depending on
method) by the Initiator and the Responder, respectively, see method) by the Initiator and the Responder, respectively, see
Section 5.5 and Section 5.4. Section 5.4 and Section 5.3.
When the credential is a certificate, CRED_x is an end-entity When the credential is a certificate, CRED_x is an end-entity
certificate (i.e. not the certificate chain) encoded as a CBOR bstr. certificate (i.e. not the certificate chain) encoded as a CBOR bstr.
In X.509 certificates, signature keys typically have key usage In X.509 certificates, signature keys typically have key usage
"digitalSignature" and Diffie-Hellman keys typically have key usage "digitalSignature" and Diffie-Hellman keys typically have key usage
"keyAgreement". "keyAgreement".
To prevent misbinding attacks in systems where an attacker can To prevent misbinding attacks in systems where an attacker can
register public keys without proving knowledge of the private key, register public keys without proving knowledge of the private key,
SIGMA [SIGMA] enforces a MAC to be calculated over the "Identity", SIGMA [SIGMA] enforces a MAC to be calculated over the "Identity",
skipping to change at page 14, line 32 skipping to change at page 14, line 19
key, and optionally the "Identity". CRED_x needs to be defined such key, and optionally the "Identity". CRED_x needs to be defined such
that it is identical when generated by Initiator or Responder. The that it is identical when generated by Initiator or Responder. The
parameters SHALL be encoded in bytewise lexicographic order of their parameters SHALL be encoded in bytewise lexicographic order of their
deterministic encodings as specified in Section 4.2.1 of [RFC8949]. deterministic encodings as specified in Section 4.2.1 of [RFC8949].
If the parties have agreed on an identity besides the public key, the If the parties have agreed on an identity besides the public key, the
identity is included in the CBOR map with the label "subject name", identity is included in the CBOR map with the label "subject name",
otherwise the subject name is the empty text string. The public key otherwise the subject name is the empty text string. The public key
parameters depend on key type. parameters depend on key type.
* For COSE_Keys of type OKP the CBOR map SHALL, except for subject o For COSE_Keys of type OKP the CBOR map SHALL, except for subject
name, only include the parameters 1 (kty), -1 (crv), and -2 name, only include the parameters 1 (kty), -1 (crv), and -2
(x-coordinate). (x-coordinate).
* For COSE_Keys of type EC2 the CBOR map SHALL, except for subject o For COSE_Keys of type EC2 the CBOR map SHALL, except for subject
name, only include the parameters 1 (kty), -1 (crv), -2 name, only include the parameters 1 (kty), -1 (crv), -2
(x-coordinate), and -3 (y-coordinate). (x-coordinate), and -3 (y-coordinate).
An example of CRED_x when the RPK contains an X25519 static Diffie- An example of CRED_x when the RPK contains an X25519 static Diffie-
Hellman key and the parties have agreed on an EUI-64 identity is Hellman key and the parties have agreed on an EUI-64 identity is
shown below: shown below:
CRED_x = { CRED_x = {
1: 1, 1: 1,
-1: 4, -1: 4,
-2: h'b1a3e89460e88d3a8d54211dc95f0b90 -2: h'b1a3e89460e88d3a8d54211dc95f0b90
3ff205eb71912d6db8f4af980d2db83a', 3ff205eb71912d6db8f4af980d2db83a',
"subject name" : "42-50-31-FF-EF-37-32-39" "subject name" : "42-50-31-FF-EF-37-32-39"
} }
3.3.4. Identification of Credentials 3.5.4. Identification of Credentials
ID_CRED_I and ID_CRED_R are used to identify and optionally transport ID_CRED_I and ID_CRED_R are used to identify and optionally transport
the public authentication keys of the Initiator and the Responder, the public authentication keys of the Initiator and the Responder,
respectively. ID_CRED_I and ID_CRED_R do not have any cryptographic respectively. ID_CRED_I and ID_CRED_R do not have any cryptographic
purpose in EDHOC. purpose in EDHOC.
* ID_CRED_R is intended to facilitate for the Initiator to retrieve o ID_CRED_R is intended to facilitate for the Initiator to retrieve
the Responder's public authentication key. the Responder's public authentication key.
* ID_CRED_I is intended to facilitate for the Responder to retrieve o ID_CRED_I is intended to facilitate for the Responder to retrieve
the Initiator's public authentication key. the Initiator's public authentication key.
The identifiers ID_CRED_I and ID_CRED_R are COSE header_maps, i.e. The identifiers ID_CRED_I and ID_CRED_R are COSE header_maps, i.e.
CBOR maps containing Common COSE Header Parameters, see Section 3.1 CBOR maps containing Common COSE Header Parameters, see Section 3.1
of [I-D.ietf-cose-rfc8152bis-struct]). In the following we give some of [I-D.ietf-cose-rfc8152bis-struct]). In the following we give some
examples of COSE header_maps. examples of COSE header_maps.
Raw public keys are most optimally stored as COSE_Key objects and Raw public keys are most optimally stored as COSE_Key objects and
identified with a 'kid' parameter: identified with a 'kid2' parameter (see Section 8.6 and Section 8.7):
* ID_CRED_x = { 4 : kid_x }, where kid_x : bstr, for x = I or R. o ID_CRED_x = { 4 : kid_x }, where kid_x : bstr / int, for x = I or
R.
Note that the integers -24 to 23 and the empty bytestring h'' are
encoded as one byte.
Public key certificates can be identified in different ways. Header Public key certificates can be identified in different ways. Header
parameters for identifying C509 certificates and X.509 certificates parameters for identifying C509 certificates and X.509 certificates
are defined in [I-D.ietf-cose-cbor-encoded-cert] and are defined in [I-D.ietf-cose-cbor-encoded-cert] and
[I-D.ietf-cose-x509], for example: [I-D.ietf-cose-x509], for example:
* by a hash value with the 'c5t' or 'x5t' parameters; o by a hash value with the 'c5t' or 'x5t' parameters;
- ID_CRED_x = { 34 : COSE_CertHash }, for x = I or R, * ID_CRED_x = { 34 : COSE_CertHash }, for x = I or R,
- ID_CRED_x = { TDB3 : COSE_CertHash }, for x = I or R, * ID_CRED_x = { TDB3 : COSE_CertHash }, for x = I or R,
* by a URI with the 'c5u' or 'x5u' parameters; o by a URI with the 'c5u' or 'x5u' parameters;
- ID_CRED_x = { 35 : uri }, for x = I or R, * ID_CRED_x = { 35 : uri }, for x = I or R,
- ID_CRED_x = { TBD4 : uri }, for x = I or R, * ID_CRED_x = { TBD4 : uri }, for x = I or R,
* ID_CRED_x MAY contain the actual credential used for o ID_CRED_x MAY contain the actual credential used for
authentication, CRED_x. For example, a certificate chain can be authentication, CRED_x. For example, a certificate chain can be
transported in ID_CRED_x with COSE header parameter c5c or transported in ID_CRED_x with COSE header parameter c5c or
x5chain, defined in [I-D.ietf-cose-cbor-encoded-cert] and x5chain, defined in [I-D.ietf-cose-cbor-encoded-cert] and
[I-D.ietf-cose-x509]. [I-D.ietf-cose-x509].
It is RECOMMENDED that ID_CRED_x uniquely identify the public It is RECOMMENDED that ID_CRED_x uniquely identify the public
authentication key as the recipient may otherwise have to try several authentication key as the recipient may otherwise have to try several
keys. ID_CRED_I and ID_CRED_R are transported in the 'ciphertext', keys. ID_CRED_I and ID_CRED_R are transported in the 'ciphertext',
see Section 5.5 and Section 5.4. see Section 5.4 and Section 5.3.
When ID_CRED_x does not contain the actual credential it may be very When ID_CRED_x does not contain the actual credential it may be very
short. One byte credential identifiers are realistic in many short. One byte credential identifiers are realistic in many
scenarios as most constrained devices only have a few keys. In cases scenarios as most constrained devices only have a few keys. In cases
where a node only has one key, the identifier may even be the empty where a node only has one key, the identifier may even be the empty
byte string. byte string.
3.4. Cipher Suites 3.6. Cipher Suites
An EDHOC cipher suite consists of an ordered set of algorithms from An EDHOC cipher suite consists of an ordered set of algorithms from
the "COSE Algorithms" and "COSE Elliptic Curves" registries. the "COSE Algorithms" and "COSE Elliptic Curves" registries.
Algorithms need to be specified with enough parameters to make them Algorithms need to be specified with enough parameters to make them
completely determined. Currently, none of the algorithms require completely determined. Currently, none of the algorithms require
parameters. EDHOC is only specified for use with key exchange parameters. EDHOC is only specified for use with key exchange
algorithms of type ECDH curves. Use with other types of key exchange algorithms of type ECDH curves. Use with other types of key exchange
algorithms would likely require a specification updating EDHOC. Note algorithms would likely require a specification updating EDHOC. Note
that for most signature algorithms, the signature is determined by that for most signature algorithms, the signature is determined by
the signature algorithm and the authentication key algorithm the signature algorithm and the authentication key algorithm
together, see Section 3.3.1. together, see Section 3.5.1.
* EDHOC AEAD algorithm o EDHOC AEAD algorithm
* EDHOC hash algorithm o EDHOC hash algorithm
* EDHOC key exchange algorithm (ECDH curve) o EDHOC key exchange algorithm (ECDH curve)
* EDHOC signature algorithm o EDHOC signature algorithm
* Application AEAD algorithm o Application AEAD algorithm
* Application hash algorithm o Application hash algorithm
Each cipher suite is identified with a pre-defined int label. Each cipher suite is identified with a pre-defined int label.
EDHOC can be used with all algorithms and curves defined for COSE. EDHOC can be used with all algorithms and curves defined for COSE.
Implementation can either use one of the pre-defined cipher suites Implementation can either use one of the pre-defined cipher suites
(Section 9.2) or use any combination of COSE algorithms and (Section 8.2) or use any combination of COSE algorithms and
parameters to define their own private cipher suite. Private cipher parameters to define their own private cipher suite. Private cipher
suites can be identified with any of the four values -24, -23, -22, suites can be identified with any of the four values -24, -23, -22,
-21. -21.
The following cipher suites are for constrained IoT where message The following CCM cipher suites are for constrained IoT where message
overhead is a very important factor: overhead is a very important factor. Cipher suites 1 and 3 use a
larger tag length (128-bit) in the EDHOC AEAD algorithm than the
Application AEAD algorithm (64-bit):
0. ( 10, -16, 4, -8, 10, -16 ) 0. ( 10, -16, 4, -8, 10, -16 )
(AES-CCM-16-64-128, SHA-256, X25519, EdDSA, (AES-CCM-16-64-128, SHA-256, X25519, EdDSA,
AES-CCM-16-64-128, SHA-256) AES-CCM-16-64-128, SHA-256)
1. ( 30, -16, 4, -8, 10, -16 ) 1. ( 30, -16, 4, -8, 10, -16 )
(AES-CCM-16-128-128, SHA-256, X25519, EdDSA, (AES-CCM-16-128-128, SHA-256, X25519, EdDSA,
AES-CCM-16-64-128, SHA-256) AES-CCM-16-64-128, SHA-256)
2. ( 10, -16, 1, -7, 10, -16 ) 2. ( 10, -16, 1, -7, 10, -16 )
(AES-CCM-16-64-128, SHA-256, P-256, ES256, (AES-CCM-16-64-128, SHA-256, P-256, ES256,
AES-CCM-16-64-128, SHA-256) AES-CCM-16-64-128, SHA-256)
3. ( 30, -16, 1, -7, 10, -16 ) 3. ( 30, -16, 1, -7, 10, -16 )
(AES-CCM-16-128-128, SHA-256, P-256, ES256, (AES-CCM-16-128-128, SHA-256, P-256, ES256,
AES-CCM-16-64-128, SHA-256) AES-CCM-16-64-128, SHA-256)
The following cipher suite is for general non-constrained The following ChaCha20 cipher suites are for less constrained
applications. It uses very high performance algorithms that also are applications and only use 128-bit tag lengths.
widely supported:
4. ( 1, -16, 4, -7, 1, -16 ) 4. ( 24, -16, 4, -8, 24, -16 )
(ChaCha20/Poly1305, SHA-256, X25519, EdDSA,
ChaCha20/Poly1305, SHA-256)
5. ( 24, -16, 1, -7, 24, -16 )
(ChaCha20/Poly1305, SHA-256, P-256, ES256,
ChaCha20/Poly1305, SHA-256)
The following GCM cipher suite is for general non-constrained
applications. It uses high performance algorithms that are widely
supported:
6. ( 1, -16, 4, -7, 1, -16 )
(A128GCM, SHA-256, X25519, ES256, (A128GCM, SHA-256, X25519, ES256,
A128GCM, SHA-256) A128GCM, SHA-256)
The following cipher suite is for high security application such as The following two cipher suites are for high security application
government use and financial applications. It is compatible with the such as government use and financial applications. The two cipher
CNSA suite [CNSA]. suites do not share any algorithms. The first of the two cipher
suites is compatible with the CNSA suite [CNSA].
5. ( 3, -43, 2, -35, 3, -43 ) 24. ( 3, -43, 2, -35, 3, -43 )
(A256GCM, SHA-384, P-384, ES384, (A256GCM, SHA-384, P-384, ES384,
A256GCM, SHA-384) A256GCM, SHA-384)
25. ( 24, -45, 5, -8, 24, -45 )
(ChaCha20/Poly1305, SHAKE256, X448, EdDSA,
ChaCha20/Poly1305, SHAKE256)
The different methods use the same cipher suites, but some algorithms The different methods use the same cipher suites, but some algorithms
are not used in some methods. The EDHOC signature algorithm is not are not used in some methods. The EDHOC signature algorithm is not
used in methods without signature authentication. used in methods without signature authentication.
The Initiator needs to have a list of cipher suites it supports in The Initiator needs to have a list of cipher suites it supports in
order of preference. The Responder needs to have a list of cipher order of preference. The Responder needs to have a list of cipher
suites it supports. SUITES_I is a CBOR array containing cipher suites it supports. SUITES_I is a CBOR array containing cipher
suites that the Initiator supports. SUITES_I is formatted and suites that the Initiator supports. SUITES_I is formatted and
processed as detailed in Section 5.3.1 to secure the cipher suite processed as detailed in Section 5.2.1 to secure the cipher suite
negotiation. Examples of cipher suite negotiation are given in negotiation. Examples of cipher suite negotiation are given in
Section 6.3.2. Section 6.3.2.
3.5. Ephemeral Public Keys 3.7. Ephemeral Public Keys
EDHOC always uses compact representation of elliptic curve points, EDHOC always uses compact representation of elliptic curve points,
see Appendix A. In COSE compact representation is achieved by see Appendix B. In COSE compact representation is achieved by
formatting the ECDH ephemeral public keys as COSE_Keys of type EC2 or formatting the ECDH ephemeral public keys as COSE_Keys of type EC2 or
OKP according to Sections 7.1 and 7.2 of OKP according to Sections 7.1 and 7.2 of
[I-D.ietf-cose-rfc8152bis-algs], but only including the 'x' parameter [I-D.ietf-cose-rfc8152bis-algs], but only including the 'x' parameter
in G_X and G_Y. For Elliptic Curve Keys of type EC2, compact in G_X and G_Y. For Elliptic Curve Keys of type EC2, compact
representation MAY be used also in the COSE_Key. If the COSE representation MAY be used also in the COSE_Key. If the COSE
implementation requires an 'y' parameter, the value y = false SHALL implementation requires an 'y' parameter, the value y = false SHALL
be used. COSE always use compact output for Elliptic Curve Keys of be used. COSE always use compact output for Elliptic Curve Keys of
type EC2. type EC2.
3.6. External Authorization Data 3.8. External Authorization Data
In order to reduce round trips and number of messages or to simplify In order to reduce round trips and number of messages or to simplify
processing, external security applications may be integrated into processing, external security applications may be integrated into
EDHOC by transporting authorization related data together with the EDHOC by transporting authorization related data together with the
messages. One example is the transport third-party identity and messages. One example is the transport third-party identity and
authorization information protected out of scope of EDHOC authorization information protected out of scope of EDHOC
[I-D.selander-ace-ake-authz]. Another example is the embedding of a [I-D.selander-ace-ake-authz]. Another example is the embedding of a
certificate enrolment request or a newly issued certificate. certificate enrolment request or a newly issued certificate.
EDHOC allows opaque external authorization data (EAD) to be sent in EDHOC allows opaque external authorization data (EAD) to be sent in
the EDHOC messages. External authorization data sent in message_1 the EDHOC messages. External authorization data sent in message_1
(EAD_1) or message_2 (EAD_2) must be considered unprotected by EDHOC, (EAD_1) or message_2 (EAD_2) must be considered unprotected by EDHOC,
see Section 8.4. External authorization data sent in message_3 see Section 7.4. External authorization data sent in message_3
(EAD_3) or message_4 (EAD_4) is protected between Initiator and (EAD_3) or message_4 (EAD_4) is protected between Initiator and
Responder. Responder.
External authorization data is a CBOR sequence (see Appendix B.1) as External authorization data is a CBOR sequence (see Appendix C.1) as
defined below: defined below:
EAD = ( EAD = (
type : int, type : int,
1* ext_authz_data : any, 1* ext_authz_data : any,
) )
where type is an int and is followed by one or more ext_authz_data where type is an int and is followed by one or more ext_authz_data
depending on type as defined in a separate specification. depending on type as defined in a separate specification.
The EAD fields of EDHOC are not intended for generic application The EAD fields of EDHOC are not intended for generic application
data. Since data carried in EAD_1 and EAD_2 fields may not be data. Since data carried in EAD_1 and EAD_2 fields may not be
protected, special considerations need to be made such that a) it protected, special considerations need to be made such that a) it
does not violate security, privacy etc. requirements of the service does not violate security, privacy etc. requirements of the service
which uses this data, and b) it does not violate the security which uses this data, and b) it does not violate the security
properties of EDHOC. Security applications making use of the EAD properties of EDHOC. Security applications making use of the EAD
fields must perform the necessary security analysis. fields must perform the necessary security analysis.
3.7. Applicability Statement 3.9. Applicability Statement
EDHOC requires certain parameters to be agreed upon between Initiator EDHOC requires certain parameters to be agreed upon between Initiator
and Responder. Some parameters can be agreed through the protocol and Responder. Some parameters can be agreed through the protocol
execution (specifically cipher suite negotiation, see Section 3.4) execution (specifically cipher suite negotiation, see Section 3.6)
but other parameters may need to be known out-of-band (e.g., which but other parameters may need to be known out-of-band (e.g., which
authentication method is used, see Section 3.2.1). authentication method is used, see Section 3.2).
The purpose of the applicability statement is describe the intended The purpose of the applicability statement is describe the intended
use of EDHOC to allow for the relevant processing and verifications use of EDHOC to allow for the relevant processing and verifications
to be made, including things like: to be made, including things like:
1. How the endpoint detects that an EDHOC message is received. This 1. How the endpoint detects that an EDHOC message is received. This
includes how EDHOC messages are transported, for example in the includes how EDHOC messages are transported, for example in the
payload of a CoAP message with a certain Uri-Path or Content- payload of a CoAP message with a certain Uri-Path or Content-
Format; see Section 7.2. Format; see Appendix A.3. * The method of transporting EDHOC
messages may also describe data carried along with the messages
2. Method and correlation of underlying transport messages that are needed for the transport to satisfy the requirements of
(METHOD_CORR; see Section 3.2.1 and Section 3.2.4). This gives Section 3.4, e.g., connection identifiers used with certain
information about the optional connection identifier fields. messages, see Appendix A.3.
3. How message_1 is identified, in particular if the optional 2. Authentication method (METHOD; see Section 3.2).
initial C_1 = "null" of message_1 is present; see Section 5.3.1
4. Profile for authentication credentials (CRED_I, CRED_R; see 3. Profile for authentication credentials (CRED_I, CRED_R; see
Section 3.3.3), e.g., profile for certificate or COSE_key, Section 3.5.3), e.g., profile for certificate or COSE_key,
including supported authentication key algorithms (subject public including supported authentication key algorithms (subject public
key algorithm in X.509 certificate). key algorithm in X.509 certificate).
5. Type used to identify authentication credentials (ID_CRED_I, 4. Type used to identify authentication credentials (ID_CRED_I,
ID_CRED_R; see Section 3.3.4). ID_CRED_R; see Section 3.5.4).
6. Use and type of external authorization data (EAD_1, EAD_2, EAD_3, 5. Use and type of external authorization data (EAD_1, EAD_2, EAD_3,
EAD_4; see Section 3.6). EAD_4; see Section 3.8).
7. Identifier used as identity of endpoint; see Section 3.3.2. 6. Identifier used as identity of endpoint; see Section 3.5.2.
8. If message_4 shall be sent/expected, and if not, how to ensure a 7. If message_4 shall be sent/expected, and if not, how to ensure a
protected application message is sent from the Responder to the protected application message is sent from the Responder to the
Initiator; see Section 7.1. Initiator; see Section 5.5.
The applicability statement may also contain information about The applicability statement may also contain information about
supported cipher suites. The procedure for selecting and verifying supported cipher suites. The procedure for selecting and verifying
cipher suite is still performed as specified by the protocol, but it cipher suite is still performed as specified by the protocol, but it
may become simplified by this knowledge. may become simplified by this knowledge.
An example of an applicability statement is shown in Appendix D. An example of an applicability statement is shown in Appendix E.
For some parameters, like METHOD_CORR, ID_CRED_x, type of EAD, the For some parameters, like METHOD, ID_CRED_x, type of EAD, the
receiver is able to verify compliance with applicability statement, receiver is able to verify compliance with applicability statement,
and if it needs to fail because of incompliance, to infer the reason and if it needs to fail because of incompliance, to infer the reason
why the protocol failed. why the protocol failed.
For other parameters, like CRED_x in the case that it is not For other parameters, like CRED_x in the case that it is not
transported, it may not be possible to verify that incompliance with transported, it may not be possible to verify that incompliance with
applicability statement was the reason for failure: Integrity applicability statement was the reason for failure: Integrity
verification in message_2 or message_3 may fail not only because of verification in message_2 or message_3 may fail not only because of
wrong authentication credential. For example, in case the Initiator wrong authentication credential. For example, in case the Initiator
uses public key certificate by reference (i.e. not transported within uses public key certificate by reference (i.e. not transported within
skipping to change at page 21, line 18 skipping to change at page 21, line 29
If the EDHOC hash algorithm is SHAKE256, then Extract( salt, IKM ) = If the EDHOC hash algorithm is SHAKE256, then Extract( salt, IKM ) =
KMAC256( salt, IKM, 512, "" ). KMAC256( salt, IKM, 512, "" ).
PRK_2e is used to derive a keystream to encrypt message_2. PRK_3e2m PRK_2e is used to derive a keystream to encrypt message_2. PRK_3e2m
is used to derive keys and IVs to produce a MAC in message_2 and to is used to derive keys and IVs to produce a MAC in message_2 and to
encrypt message_3. PRK_4x3m is used to derive keys and IVs to encrypt message_3. PRK_4x3m is used to derive keys and IVs to
produce a MAC in message_3 and to derive application specific data. produce a MAC in message_3 and to derive application specific data.
PRK_2e is derived with the following input: PRK_2e is derived with the following input:
* The salt SHALL be the empty byte string. Note that [RFC5869] o The salt SHALL be the empty byte string. Note that [RFC5869]
specifies that if the salt is not provided, it is set to a string specifies that if the salt is not provided, it is set to a string
of zeros (see Section 2.2 of [RFC5869]). For implementation of zeros (see Section 2.2 of [RFC5869]). For implementation
purposes, not providing the salt is the same as setting the salt purposes, not providing the salt is the same as setting the salt
to the empty byte string. to the empty byte string.
* The input keying material (IKM) SHALL be the ECDH shared secret o The input keying material (IKM) SHALL be the ECDH shared secret
G_XY (calculated from G_X and Y or G_Y and X) as defined in G_XY (calculated from G_X and Y or G_Y and X) as defined in
Section 6.3.1 of [I-D.ietf-cose-rfc8152bis-algs]. Section 6.3.1 of [I-D.ietf-cose-rfc8152bis-algs].
Example: Assuming the use of SHA-256 the extract phase of HKDF Example: Assuming the use of SHA-256 the extract phase of HKDF
produces PRK_2e as follows: produces PRK_2e as follows:
PRK_2e = HMAC-SHA-256( salt, G_XY ) PRK_2e = HMAC-SHA-256( salt, G_XY )
where salt = 0x (the empty byte string). where salt = 0x (the empty byte string).
The pseudorandom keys PRK_3e2m and PRK_4x3m are defined as follow: The pseudorandom keys PRK_3e2m and PRK_4x3m are defined as follow:
* If the Responder authenticates with a static Diffie-Hellman key, o If the Responder authenticates with a static Diffie-Hellman key,
then PRK_3e2m = Extract( PRK_2e, G_RX ), where G_RX is the ECDH then PRK_3e2m = Extract( PRK_2e, G_RX ), where G_RX is the ECDH
shared secret calculated from G_R and X, or G_X and R, else shared secret calculated from G_R and X, or G_X and R, else
PRK_3e2m = PRK_2e. PRK_3e2m = PRK_2e.
* If the Initiator authenticates with a static Diffie-Hellman key, o If the Initiator authenticates with a static Diffie-Hellman key,
then PRK_4x3m = Extract( PRK_3e2m, G_IY ), where G_IY is the ECDH then PRK_4x3m = Extract( PRK_3e2m, G_IY ), where G_IY is the ECDH
shared secret calculated from G_I and Y, or G_Y and I, else shared secret calculated from G_I and Y, or G_Y and I, else
PRK_4x3m = PRK_3e2m. PRK_4x3m = PRK_3e2m.
Example: Assuming the use of curve25519, the ECDH shared secrets Example: Assuming the use of curve25519, the ECDH shared secrets
G_XY, G_RX, and G_IY are the outputs of the X25519 function G_XY, G_RX, and G_IY are the outputs of the X25519 function
[RFC7748]: [RFC7748]:
G_XY = X25519( Y, G_X ) = X25519( X, G_Y ) G_XY = X25519( Y, G_X ) = X25519( X, G_Y )
skipping to change at page 22, line 23 skipping to change at page 22, line 34
info = [ info = [
edhoc_aead_id : int / tstr, edhoc_aead_id : int / tstr,
transcript_hash : bstr, transcript_hash : bstr,
label : tstr, label : tstr,
length : uint length : uint
] ]
where where
* edhoc_aead_id is an int or tstr containing the algorithm o edhoc_aead_id is an int or tstr containing the algorithm
identifier of the EDHOC AEAD algorithm in the selected cipher identifier of the EDHOC AEAD algorithm in the selected cipher
suite encoded as defined in [I-D.ietf-cose-rfc8152bis-algs]. Note suite encoded as defined in [I-D.ietf-cose-rfc8152bis-algs]. Note
that a single fixed edhoc_aead_id is used in all invocations of that a single fixed edhoc_aead_id is used in all invocations of
EDHOC-KDF, including the derivation of KEYSTREAM_2 and invocations EDHOC-KDF, including the derivation of KEYSTREAM_2 and invocations
of the EDHOC-Exporter. of the EDHOC-Exporter.
* transcript_hash is a bstr set to one of the transcript hashes o transcript_hash is a bstr set to one of the transcript hashes
TH_2, TH_3, or TH_4 as defined in Sections 5.4.1, 5.5.1, and 4.1. TH_2, TH_3, or TH_4 as defined in Sections 5.3.1, 5.4.1, and 4.1.
* label is a tstr set to the name of the derived key or IV, i.e. o label is a tstr set to the name of the derived key or IV, i.e.
"K_2m", "IV_2m", "KEYSTREAM_2", "K_3m", "IV_3m", "K_3ae", or "K_2m", "IV_2m", "KEYSTREAM_2", "K_3m", "IV_3m", "K_3ae", or
"IV_3ae". "IV_3ae".
* length is the length of output keying material (OKM) in bytes o length is the length of output keying material (OKM) in bytes
If the EDHOC hash algorithm is SHA-2, then Expand( PRK, info, length If the EDHOC hash algorithm is SHA-2, then Expand( PRK, info, length
) = HKDF-Expand( PRK, info, length ) [RFC5869]. If the EDHOC hash ) = HKDF-Expand( PRK, info, length ) [RFC5869]. If the EDHOC hash
algorithm is SHAKE128, then Expand( PRK, info, length ) = KMAC128( algorithm is SHAKE128, then Expand( PRK, info, length ) = KMAC128(
PRK, info, L, "" ). If the EDHOC hash algorithm is SHAKE256, then PRK, info, L, "" ). If the EDHOC hash algorithm is SHAKE256, then
Expand( PRK, info, length ) = KMAC256( PRK, info, L, "" ). Expand( PRK, info, length ) = KMAC256( PRK, info, L, "" ).
KEYSTREAM_2 are derived using the transcript hash TH_2 and the KEYSTREAM_2 are derived using the transcript hash TH_2 and the
pseudorandom key PRK_2e. K_2m and IV_2m are derived using the pseudorandom key PRK_2e. K_2m and IV_2m are derived using the
transcript hash TH_2 and the pseudorandom key PRK_3e2m. K_3ae and transcript hash TH_2 and the pseudorandom key PRK_3e2m. K_3ae and
skipping to change at page 23, line 21 skipping to change at page 23, line 31
= EDHOC-KDF(PRK_4x3m, TH_4, label_context, length) = EDHOC-KDF(PRK_4x3m, TH_4, label_context, length)
label_context is a CBOR sequence: label_context is a CBOR sequence:
label_context = ( label_context = (
label : tstr, label : tstr,
context : bstr, context : bstr,
) )
where label is a registered tstr from the EDHOC Exporter Label where label is a registered tstr from the EDHOC Exporter Label
registry (Section 9.1), context is a bstr defined by the application, registry (Section 8.1), context is a bstr defined by the application,
and length is a uint defined by the application. The (label, and length is a uint defined by the application. The (label,
context) pair must be unique, i.e. a (label, context) MUST NOT be context) pair must be unique, i.e. a (label, context) MUST NOT be
used for two different purposes. However an application can re- used for two different purposes. However an application can re-
derive the same key several times as long as it is done in a secure derive the same key several times as long as it is done in a secure
way. For example, in most encryption algorithms the same (key, way. For example, in most encryption algorithms the same (key,
nonce) pair must not be reused. nonce) pair must not be reused.
The transcript hash TH_4 is a CBOR encoded bstr and the input to the The transcript hash TH_4 is a CBOR encoded bstr and the input to the
hash function is a CBOR Sequence. hash function is a CBOR Sequence.
TH_4 = H( TH_3, CIPHERTEXT_3 ) TH_4 = H( TH_3, CIPHERTEXT_3 )
where H() is the hash function in the selected cipher suite. where H() is the hash function in the selected cipher suite.
Examples of use of the EDHOC-Exporter are given in Section 7.1.2 and Examples of use of the EDHOC-Exporter are given in Section 5.5.2 and
[I-D.ietf-core-oscore-edhoc]. Appendix A.
To provide forward secrecy in an even more efficient way than re- To provide forward secrecy in an even more efficient way than re-
running EDHOC, EDHOC provides the function EDHOC-KeyUpdate. When running EDHOC, EDHOC provides the function EDHOC-KeyUpdate. When
EDHOC-KeyUpdate is called the old PRK_4x3m is deleted and the new EDHOC-KeyUpdate is called the old PRK_4x3m is deleted and the new
PRK_4x3m is calculated as a "hash" of the old key using the Extract PRK_4x3m is calculated as a "hash" of the old key using the Extract
function as illustrated by the following pseudocode: function as illustrated by the following pseudocode:
EDHOC-KeyUpdate( nonce ): EDHOC-KeyUpdate( nonce ):
PRK_4x3m = Extract( nonce, PRK_4x3m ) PRK_4x3m = Extract( nonce, PRK_4x3m )
skipping to change at page 24, line 15 skipping to change at page 24, line 25
An EDHOC message is encoded as a sequence of CBOR data (CBOR An EDHOC message is encoded as a sequence of CBOR data (CBOR
Sequence, [RFC8742]). Additional optimizations are made to reduce Sequence, [RFC8742]). Additional optimizations are made to reduce
message overhead. message overhead.
While EDHOC uses the COSE_Key, COSE_Sign1, and COSE_Encrypt0 While EDHOC uses the COSE_Key, COSE_Sign1, and COSE_Encrypt0
structures, only a subset of the parameters is included in the EDHOC structures, only a subset of the parameters is included in the EDHOC
messages. The unprotected COSE header in COSE_Sign1, and messages. The unprotected COSE header in COSE_Sign1, and
COSE_Encrypt0 (not included in the EDHOC message) MAY contain COSE_Encrypt0 (not included in the EDHOC message) MAY contain
parameters (e.g. 'alg'). parameters (e.g. 'alg').
5.1. Encoding of bstr_identifier 5.1. Message Processing Outline
Byte strings are encoded in CBOR as two or more bytes, whereas
integers in the interval -24 to 23 are encoded in CBOR as one byte.
bstr_identifier is a special encoding of byte strings, used
throughout the protocol to enable the encoding of the shortest byte
strings as integers that only require one byte of CBOR encoding.
The bstr_identifier encoding is defined as follows: Byte strings in
the interval h'00' to h'2f' are encoded as the corresponding integer
minus 24, which are all represented by one byte CBOR ints. Other
byte strings are encoded as CBOR byte strings.
For example, the byte string h'59e9' encoded as a bstr_identifier is
equal to h'59e9', while the byte string h'2a' is encoded as the
integer 18.
The CDDL definition of the bstr_identifier is given below:
bstr_identifier = bstr / int
Note that, despite what could be interpreted by the CDDL definition
only, bstr_identifier once decoded are always byte strings.
5.2. Message Processing Outline
This section outlines the message processing of EDHOC. This section outlines the message processing of EDHOC.
For each session, the endpoints are assumed to keep an associated For each session, the endpoints are assumed to keep an associated
protocol state containing connection identifiers, keys, etc. used for protocol state containing identifiers, keys, etc. used for subsequent
subsequent processing of protocol related data. The protocol state processing of protocol related data. The protocol state is assumed
is assumed to be associated to an applicability statement to be associated to an applicability statement (Section 3.9) which
(Section 3.7) which provides the context for how messages are provides the context for how messages are transported, identified and
transported, identified and processed. processed.
EDHOC messages SHALL be processed according to the current protocol EDHOC messages SHALL be processed according to the current protocol
state. The following steps are expected to be performed at reception state. The following steps are expected to be performed at reception
of an EDHOC message: of an EDHOC message:
1. Detect that an EDHOC message has been received, for example by 1. Detect that an EDHOC message has been received, for example by
means of port number, URI, or media type (Section 3.7). means of port number, URI, or media type (Section 3.9).
2. Retrieve the protocol state, e.g. using the received connection 2. Retrieve the protocol state according to the message correlation
identifier (Section 3.2.2) or with the help of message provided by the transport, see Section 3.4. If there is no
correlation provided by the transport protocol (Section 3.2.4). protocol state, in the case of message_1, a new protocol state is
If there is no protocol state, in the case of message_1, a new created. The Responder endpoint needs to make use of available
protocol state is created. An initial C_1 = "null" byte in Denial-of-Service mitigation (Section 7.5).
message_1 (Section 5.3.1) can be used to distinguish message_1
from other messages. The Responder endpoint needs to make use of
available Denial-of-Service mitigation (Section 8.5).
3. If the message received is an error message then process 3. If the message received is an error message then process
according to Section 6, else process as the expected next message according to Section 6, else process as the expected next message
according to the protocol state. according to the protocol state.
If the processing fails, then the protocol is discontinued, an error If the processing fails, then the protocol is discontinued, an error
message sent, and the protocol state erased. Further details are message sent, and the protocol state erased. Further details are
provided in the following subsections. provided in the following subsections.
Different instances of the same message MUST NOT be processed in one Different instances of the same message MUST NOT be processed in one
session. Note that processing will fail if the same message appears session. Note that processing will fail if the same message appears
a second time for EDHOC processing because the state of the protocol a second time for EDHOC processing because the state of the protocol
has moved on and now expects something else. This assumes that has moved on and now expects something else. This assumes that
message duplication due to re-transmissions is handled by the message duplication due to re-transmissions is handled by the
transport protocol, see Section 3.2.3. The case when the transport transport protocol, see Section 3.4. The case when the transport
does not support message deduplication is addressed in Appendix E. does not support message deduplication is addressed in Appendix F.
5.3. EDHOC Message 1 5.2. EDHOC Message 1
5.3.1. Formatting of Message 1 5.2.1. Formatting of Message 1
message_1 SHALL be a CBOR Sequence (see Appendix B.1) as defined message_1 SHALL be a CBOR Sequence (see Appendix C.1) as defined
below below
message_1 = ( message_1 = (
? C_1 : null, METHOD : int,
METHOD_CORR : int,
SUITES_I : [ selected : suite, supported : 2* suite ] / suite, SUITES_I : [ selected : suite, supported : 2* suite ] / suite,
G_X : bstr, G_X : bstr,
C_I : bstr_identifier, C_I : bstr / int,
? EAD ; EAD_1 ? EAD ; EAD_1
) )
suite = int suite = int
where: where:
* C_1 - an initial CBOR simple value "null" (= 0xf6) MAY be used to o METHOD = 0, 1, 2, or 3 (see Figure 4).
distinguish message_1 from other messages.
* METHOD_CORR = 4 * method + corr, where method = 0, 1, 2, or 3 (see
Figure 4) and the correlation parameter corr is chosen based on
the transport and determines which connection identifiers that are
omitted (see Section 3.2.4).
* SUITES_I - cipher suites which the Initiator supports in order of o SUITES_I - cipher suites which the Initiator supports in order of
(decreasing) preference. The list of supported cipher suites can (decreasing) preference. The list of supported cipher suites can
be truncated at the end, as is detailed in the processing steps be truncated at the end, as is detailed in the processing steps
below and Section 6.3. One of the supported cipher suites is below and Section 6.3. One of the supported cipher suites is
selected. The selected suite is the first suite in the SUITES_I selected. The selected suite is the first suite in the SUITES_I
CBOR array. If a single supported cipher suite is conveyed then CBOR array. If a single supported cipher suite is conveyed then
that cipher suite is selected and SUITES_I is encoded as an int that cipher suite is selected and SUITES_I is encoded as an int
instead of an array. instead of an array.
* G_X - the ephemeral public key of the Initiator o G_X - the ephemeral public key of the Initiator
* C_I - variable length connection identifier, encoded as a o C_I - variable length connection identifier
bstr_identifier (see Section 5.1).
* EAD_1 - unprotected external authorization data, see Section 3.6. o EAD_1 - unprotected external authorization data, see Section 3.8.
5.3.2. Initiator Processing of Message 1 5.2.2. Initiator Processing of Message 1
The Initiator SHALL compose message_1 as follows: The Initiator SHALL compose message_1 as follows:
* The supported cipher suites and the order of preference MUST NOT o The supported cipher suites and the order of preference MUST NOT
be changed based on previous error messages. However, the list be changed based on previous error messages. However, the list
SUITES_I sent to the Responder MAY be truncated such that cipher SUITES_I sent to the Responder MAY be truncated such that cipher
suites which are the least preferred are omitted. The amount of suites which are the least preferred are omitted. The amount of
truncation MAY be changed between sessions, e.g. based on previous truncation MAY be changed between sessions, e.g. based on previous
error messages (see next bullet), but all cipher suites which are error messages (see next bullet), but all cipher suites which are
more preferred than the least preferred cipher suite in the list more preferred than the least preferred cipher suite in the list
MUST be included in the list. MUST be included in the list.
* The Initiator MUST select its most preferred cipher suite, o The Initiator MUST select its most preferred cipher suite,
conditioned on what it can assume to be supported by the conditioned on what it can assume to be supported by the
Responder. If the Initiator previously received from the Responder. If the Initiator previously received from the
Responder an error message with error code 2 (see Section 6.3) Responder an error message with error code 2 (see Section 6.3)
indicating cipher suites supported by the Responder which also are indicating cipher suites supported by the Responder which also are
supported by the Initiator, then the Initiator SHOULD select the supported by the Initiator, then the Initiator SHOULD select the
most preferred cipher suite of those (note that error messages are most preferred cipher suite of those (note that error messages are
not authenticated and may be forged). not authenticated and may be forged).
* Generate an ephemeral ECDH key pair using the curve in the o Generate an ephemeral ECDH key pair using the curve in the
selected cipher suite and format it as a COSE_Key. Let G_X be the selected cipher suite and format it as a COSE_Key. Let G_X be the
'x' parameter of the COSE_Key. 'x' parameter of the COSE_Key.
* Choose a connection identifier C_I and store it for the length of o Choose a connection identifier C_I and store it for the length of
the protocol. the protocol.
* Encode message_1 as a sequence of CBOR encoded data items as o Encode message_1 as a sequence of CBOR encoded data items as
specified in Section 5.3.1 specified in Section 5.2.1
5.3.3. Responder Processing of Message 1 5.2.3. Responder Processing of Message 1
The Responder SHALL process message_1 as follows: The Responder SHALL process message_1 as follows:
* Decode message_1 (see Appendix B.1). o Decode message_1 (see Appendix C.1).
* Verify that the selected cipher suite is supported and that no o Verify that the selected cipher suite is supported and that no
prior cipher suite in SUITES_I is supported. prior cipher suite in SUITES_I is supported.
* Pass EAD_1 to the security application. o Pass EAD_1 to the security application.
If any processing step fails, the Responder SHOULD send an EDHOC If any processing step fails, the Responder SHOULD send an EDHOC
error message back, formatted as defined in Section 6, and the error message back, formatted as defined in Section 6, and the
session MUST be discontinued. Sending error messages is essential session MUST be discontinued. Sending error messages is essential
for debugging but MAY e.g. be skipped due to denial of service for debugging but MAY e.g. be skipped due to denial of service
reasons, see Section 8. reasons, see Section 7.
5.4. EDHOC Message 2 5.3. EDHOC Message 2
5.4.1. Formatting of Message 2 5.3.1. Formatting of Message 2
message_2 and data_2 SHALL be CBOR Sequences (see Appendix B.1) as message_2 and data_2 SHALL be CBOR Sequences (see Appendix C.1) as
defined below defined below
message_2 = ( message_2 = (
data_2, data_2,
CIPHERTEXT_2 : bstr, CIPHERTEXT_2 : bstr,
) )
data_2 = ( data_2 = (
? C_I : bstr_identifier,
G_Y : bstr, G_Y : bstr,
C_R : bstr_identifier, C_R : bstr / int,
) )
where: where:
* G_Y - the ephemeral public key of the Responder o G_Y - the ephemeral public key of the Responder
* C_R - variable length connection identifier, encoded as a o C_R - variable length connection identifier
bstr_identifier (see Section 5.1).
5.4.2. Responder Processing of Message 2 5.3.2. Responder Processing of Message 2
The Responder SHALL compose message_2 as follows: The Responder SHALL compose message_2 as follows:
* If corr (METHOD_CORR mod 4) equals 1 or 3, C_I is omitted, o Generate an ephemeral ECDH key pair using the curve in the
otherwise C_I is not omitted.
* Generate an ephemeral ECDH key pair using the curve in the
selected cipher suite and format it as a COSE_Key. Let G_Y be the selected cipher suite and format it as a COSE_Key. Let G_Y be the
'x' parameter of the COSE_Key. 'x' parameter of the COSE_Key.
* Choose a connection identifier C_R and store it for the length of o Choose a connection identifier C_R and store it for the length of
the protocol. the protocol.
* Compute the transcript hash TH_2 = H( H(message_1), data_2 ) where o Compute the transcript hash TH_2 = H( H(message_1), data_2 ) where
H() is the hash function in the selected cipher suite. The H() is the hash function in the selected cipher suite. The
transcript hash TH_2 is a CBOR encoded bstr and the input to the transcript hash TH_2 is a CBOR encoded bstr and the input to the
hash function is a CBOR Sequence. Note that H(message_1) can be hash function is a CBOR Sequence. Note that H(message_1) can be
computed and cached already in the processing of message_1. computed and cached already in the processing of message_1.
* Compute an inner COSE_Encrypt0 as defined in Section 5.3 of o Compute an inner COSE_Encrypt0 as defined in Section 5.3 of
[I-D.ietf-cose-rfc8152bis-struct], with the EDHOC AEAD algorithm [I-D.ietf-cose-rfc8152bis-struct], with the EDHOC AEAD algorithm
in the selected cipher suite, K_2m, IV_2m, and the following in the selected cipher suite, K_2m, IV_2m, and the following
parameters: parameters:
- protected = << ID_CRED_R >> * protected = << ID_CRED_R >>
+ ID_CRED_R - identifier to facilitate retrieval of CRED_R,
o ID_CRED_R - identifier to facilitate retrieval of CRED_R, see Section 3.5.4
see Section 3.3.4
- external_aad = << TH_2, CRED_R, ? EAD_2 >> * external_aad = << TH_2, CRED_R, ? EAD_2 >>
o CRED_R - bstr containing the credential of the Responder, + CRED_R - bstr containing the credential of the Responder,
see Section 3.3.4 see Section 3.5.4
o EAD_2 = unprotected external authorization data, see + EAD_2 = unprotected external authorization data, see
Section 3.6 Section 3.8
- plaintext = h'' * plaintext = h''
COSE constructs the input to the AEAD [RFC5116] as follows: COSE constructs the input to the AEAD [RFC5116] as follows:
- Key K = EDHOC-KDF( PRK_3e2m, TH_2, "K_2m", length ) * Key K = EDHOC-KDF( PRK_3e2m, TH_2, "K_2m", length )
- Nonce N = EDHOC-KDF( PRK_3e2m, TH_2, "IV_2m", length ) * Nonce N = EDHOC-KDF( PRK_3e2m, TH_2, "IV_2m", length )
- Plaintext P = 0x (the empty string) * Plaintext P = 0x (the empty string)
- Associated data A = * Associated data A =
[ "Encrypt0", << ID_CRED_R >>, << TH_2, CRED_R, ? EAD_2 >> ] [ "Encrypt0", << ID_CRED_R >>, << TH_2, CRED_R, ? EAD_2 >> ]
MAC_2 is the 'ciphertext' of the inner COSE_Encrypt0. MAC_2 is the 'ciphertext' of the inner COSE_Encrypt0.
* If the Responder authenticates with a static Diffie-Hellman key o If the Responder authenticates with a static Diffie-Hellman key
(method equals 1 or 3), then Signature_or_MAC_2 is MAC_2. If the (method equals 1 or 3), then Signature_or_MAC_2 is MAC_2. If the
Responder authenticates with a signature key (method equals 0 or Responder authenticates with a signature key (method equals 0 or
2), then Signature_or_MAC_2 is the 'signature' of a COSE_Sign1 2), then Signature_or_MAC_2 is the 'signature' of a COSE_Sign1
object as defined in Section 4.4 of object as defined in Section 4.4 of
[I-D.ietf-cose-rfc8152bis-struct] using the signature algorithm in [I-D.ietf-cose-rfc8152bis-struct] using the signature algorithm in
the selected cipher suite, the private authentication key of the the selected cipher suite, the private authentication key of the
Responder, and the following parameters: Responder, and the following parameters:
- protected = << ID_CRED_R >> * protected = << ID_CRED_R >>
- external_aad = << TH_2, CRED_R, ? EAD_2 >> * external_aad = << TH_2, CRED_R, ? EAD_2 >>
* payload = MAC_2
- payload = MAC_2
COSE constructs the input to the Signature Algorithm as: COSE constructs the input to the Signature Algorithm as:
- The key is the private authentication key of the Responder. * The key is the private authentication key of the Responder.
- The message M to be signed = * The message M to be signed =
[ "Signature1", << ID_CRED_R >>, << TH_2, CRED_R, ? EAD_2 >>, [ "Signature1", << ID_CRED_R >>, << TH_2, CRED_R, ? EAD_2 >>,
MAC_2 ] MAC_2 ]
* CIPHERTEXT_2 is encrypted by using the Expand function as a binary o CIPHERTEXT_2 is encrypted by using the Expand function as a binary
additive stream cipher. additive stream cipher.
- plaintext = ( ID_CRED_R / bstr_identifier, Signature_or_MAC_2, * plaintext = ( ID_CRED_R / bstr / int, Signature_or_MAC_2, ?
? EAD_2 ) EAD_2 )
o Note that if ID_CRED_R contains a single 'kid' parameter, + Note that if ID_CRED_R contains a single 'kid2' parameter,
i.e., ID_CRED_R = { 4 : kid_R }, only the byte string kid_R i.e., ID_CRED_R = { 4 : kid_R }, only the byte string or
is conveyed in the plaintext encoded as a bstr_identifier, integer kid_R is conveyed in the plaintext encoded as a bstr
see Section 3.3.4 and Section 5.1. / int.
- CIPHERTEXT_2 = plaintext XOR KEYSTREAM_2 * CIPHERTEXT_2 = plaintext XOR KEYSTREAM_2
* Encode message_2 as a sequence of CBOR encoded data items as o Encode message_2 as a sequence of CBOR encoded data items as
specified in Section 5.4.1. specified in Section 5.3.1.
5.4.3. Initiator Processing of Message 2 5.3.3. Initiator Processing of Message 2
The Initiator SHALL process message_2 as follows: The Initiator SHALL process message_2 as follows:
* Decode message_2 (see Appendix B.1). o Decode message_2 (see Appendix C.1).
* Retrieve the protocol state using the connection identifier C_I o Retrieve the protocol state using the message correlation provided
and/or other external information such as the CoAP Token and the by the transport (e.g., the CoAP Token and the 5-tuple as a
5-tuple. client, or the prepended C_I as a server).
* Decrypt CIPHERTEXT_2, see Section 5.4.2. o Decrypt CIPHERTEXT_2, see Section 5.3.2.
* Pass EAD_2 to the security application. o Pass EAD_2 to the security application.
* Verify that the identity of the Responder is an allowed identity o Verify that the identity of the Responder is an allowed identity
for this connection, see Section 3.3. for this connection, see Section 3.5.
* Verify Signature_or_MAC_2 using the algorithm in the selected o Verify Signature_or_MAC_2 using the algorithm in the selected
cipher suite. The verification process depends on the method, see cipher suite. The verification process depends on the method, see
Section 5.4.2. Section 5.3.2.
If any processing step fails, the Initiator SHOULD send an EDHOC If any processing step fails, the Initiator SHOULD send an EDHOC
error message back, formatted as defined in Section 6. Sending error error message back, formatted as defined in Section 6. Sending error
messages is essential for debugging but MAY e.g.be skipped if a messages is essential for debugging but MAY e.g.be skipped if a
session cannot be found or due to denial of service reasons, see session cannot be found or due to denial of service reasons, see
Section 8. If an error message is sent, the session MUST be Section 7. If an error message is sent, the session MUST be
discontinued. discontinued.
5.5. EDHOC Message 3 5.4. EDHOC Message 3
5.5.1. Formatting of Message 3 5.4.1. Formatting of Message 3
message_3 and data_3 SHALL be CBOR Sequences (see Appendix B.1) as message_3 SHALL be a CBOR Sequence (see Appendix C.1) as defined
defined below below
message_3 = ( message_3 = (
data_3,
CIPHERTEXT_3 : bstr, CIPHERTEXT_3 : bstr,
) )
data_3 = ( 5.4.2. Initiator Processing of Message 3
? C_R : bstr_identifier,
)
5.5.2. Initiator Processing of Message 3
The Initiator SHALL compose message_3 as follows: The Initiator SHALL compose message_3 as follows:
* If corr (METHOD_CORR mod 4) equals 2 or 3, C_R is omitted, o Compute the transcript hash TH_3 = H(TH_2, CIPHERTEXT_2) where H()
otherwise C_R is not omitted. is the hash function in the selected cipher suite. The transcript
hash TH_3 is a CBOR encoded bstr and the input to the hash
* Compute the transcript hash TH_3 = H( H(TH_2, CIPHERTEXT_2), function is a CBOR Sequence. Note that H(TH_2, CIPHERTEXT_2) can
data_3 ) where H() is the hash function in the selected cipher be computed and cached already in the processing of message_2.
suite. The transcript hash TH_3 is a CBOR encoded bstr and the
input to the hash function is a CBOR Sequence. Note that H(TH_2,
CIPHERTEXT_2) can be computed and cached already in the processing
of message_2.
* Compute an inner COSE_Encrypt0 as defined in Section 5.3 of o Compute an inner COSE_Encrypt0 as defined in Section 5.3 of
[I-D.ietf-cose-rfc8152bis-struct], with the EDHOC AEAD algorithm [I-D.ietf-cose-rfc8152bis-struct], with the EDHOC AEAD algorithm
in the selected cipher suite, K_3m, IV_3m, and the following in the selected cipher suite, K_3m, IV_3m, and the following
parameters: parameters:
- protected = << ID_CRED_I >> * protected = << ID_CRED_I >>
o ID_CRED_I - identifier to facilitate retrieval of CRED_I, + ID_CRED_I - identifier to facilitate retrieval of CRED_I,
see Section 3.3.4 see Section 3.5.4
- external_aad = << TH_3, CRED_I, ? EAD_3 >> * external_aad = << TH_3, CRED_I, ? EAD_3 >>
o CRED_I - bstr containing the credential of the Initiator,
see Section 3.3.4.
o EAD_3 = protected external authorization data, see + CRED_I - bstr containing the credential of the Initiator,
Section 3.6 see Section 3.5.4.
- plaintext = h'' + EAD_3 = protected external authorization data, see
Section 3.8
COSE constructs the input to the AEAD [RFC5116] as follows: * plaintext = h''
- Key K = EDHOC-KDF( PRK_4x3m, TH_3, "K_3m", length ) COSE constructs the input to the AEAD [RFC5116] as follows:
- Nonce N = EDHOC-KDF( PRK_4x3m, TH_3, "IV_3m", length ) * Key K = EDHOC-KDF( PRK_4x3m, TH_3, "K_3m", length )
- Plaintext P = 0x (the empty string) * Nonce N = EDHOC-KDF( PRK_4x3m, TH_3, "IV_3m", length )
- Associated data A = * Plaintext P = 0x (the empty string)
* Associated data A =
[ "Encrypt0", << ID_CRED_I >>, << TH_3, CRED_I, ? EAD_3 >> ] [ "Encrypt0", << ID_CRED_I >>, << TH_3, CRED_I, ? EAD_3 >> ]
MAC_3 is the 'ciphertext' of the inner COSE_Encrypt0. MAC_3 is the 'ciphertext' of the inner COSE_Encrypt0.
* If the Initiator authenticates with a static Diffie-Hellman key o If the Initiator authenticates with a static Diffie-Hellman key
(method equals 2 or 3), then Signature_or_MAC_3 is MAC_3. If the (method equals 2 or 3), then Signature_or_MAC_3 is MAC_3. If the
Initiator authenticates with a signature key (method equals 0 or Initiator authenticates with a signature key (method equals 0 or
1), then Signature_or_MAC_3 is the 'signature' of a COSE_Sign1 1), then Signature_or_MAC_3 is the 'signature' of a COSE_Sign1
object as defined in Section 4.4 of object as defined in Section 4.4 of
[I-D.ietf-cose-rfc8152bis-struct] using the signature algorithm in [I-D.ietf-cose-rfc8152bis-struct] using the signature algorithm in
the selected cipher suite, the private authentication key of the the selected cipher suite, the private authentication key of the
Initiator, and the following parameters: Initiator, and the following parameters:
- protected = << ID_CRED_I >> * protected = << ID_CRED_I >>
- external_aad = << TH_3, CRED_I, ? EAD_3 >> * external_aad = << TH_3, CRED_I, ? EAD_3 >>
- payload = MAC_3 * payload = MAC_3
COSE constructs the input to the Signature Algorithm as: COSE constructs the input to the Signature Algorithm as:
- The key is the private authentication key of the Initiator. * The key is the private authentication key of the Initiator.
- The message M to be signed = * The message M to be signed =
[ "Signature1", << ID_CRED_I >>, << TH_3, CRED_I, ? EAD_3 >>, [ "Signature1", << ID_CRED_I >>, << TH_3, CRED_I, ? EAD_3 >>,
MAC_3 ] MAC_3 ]
* Compute an outer COSE_Encrypt0 as defined in Section 5.3 of o Compute an outer COSE_Encrypt0 as defined in Section 5.3 of
[I-D.ietf-cose-rfc8152bis-struct], with the EDHOC AEAD algorithm [I-D.ietf-cose-rfc8152bis-struct], with the EDHOC AEAD algorithm
in the selected cipher suite, K_3ae, IV_3ae, and the following in the selected cipher suite, K_3ae, IV_3ae, and the following
parameters. The protected header SHALL be empty. parameters. The protected header SHALL be empty.
- external_aad = TH_3 * external_aad = TH_3
- plaintext = ( ID_CRED_I / bstr_identifier, Signature_or_MAC_3, * plaintext = ( ID_CRED_I / bstr / int, Signature_or_MAC_3, ?
? EAD_3 ) EAD_3 )
o Note that if ID_CRED_I contains a single 'kid' parameter, + Note that if ID_CRED_I contains a single 'kid2' parameter,
i.e., ID_CRED_I = { 4 : kid_I }, only the byte string kid_I i.e., ID_CRED_I = { 4 : kid_I }, only the byte string or
is conveyed in the plaintext encoded as a bstr_identifier, integer kid_I is conveyed in the plaintext encoded as a bstr
see Section 3.3.4 and Section 5.1. or int.
COSE constructs the input to the AEAD [RFC5116] as follows: COSE constructs the input to the AEAD [RFC5116] as follows:
- Key K = EDHOC-KDF( PRK_3e2m, TH_3, "K_3ae", length ) * Key K = EDHOC-KDF( PRK_3e2m, TH_3, "K_3ae", length )
* Nonce N = EDHOC-KDF( PRK_3e2m, TH_3, "IV_3ae", length )
- Nonce N = EDHOC-KDF( PRK_3e2m, TH_3, "IV_3ae", length )
- Plaintext P = ( ID_CRED_I / bstr_identifier, * Plaintext P = ( ID_CRED_I / bstr / int, Signature_or_MAC_3, ?
Signature_or_MAC_3, ? EAD_3 ) EAD_3 )
- Associated data A = [ "Encrypt0", h'', TH_3 ] * Associated data A = [ "Encrypt0", h'', TH_3 ]
CIPHERTEXT_3 is the 'ciphertext' of the outer COSE_Encrypt0. CIPHERTEXT_3 is the 'ciphertext' of the outer COSE_Encrypt0.
* Encode message_3 as a sequence of CBOR encoded data items as o Encode message_3 as a sequence of CBOR encoded data items as
specified in Section 5.5.1. specified in Section 5.4.1.
Pass the connection identifiers (C_I, C_R) and the application Pass the connection identifiers (C_I, C_R) and the application
algorithms in the selected cipher suite to the application. The algorithms in the selected cipher suite to the application. The
application can now derive application keys using the EDHOC-Exporter application can now derive application keys using the EDHOC-Exporter
interface. interface.
After sending message_3, the Initiator is assured that no other party After sending message_3, the Initiator is assured that no other party
than the Responder can compute the key PRK_4x3m (implicit key than the Responder can compute the key PRK_4x3m (implicit key
authentication). The Initiator can securely derive application keys authentication). The Initiator can securely derive application keys
and send protected application data. However, the Initiator does not and send protected application data. However, the Initiator does not
know that the Responder has actually computed the key PRK_4x3m and know that the Responder has actually computed the key PRK_4x3m and
therefore the Initiator SHOULD NOT permanently store the keying therefore the Initiator SHOULD NOT permanently store the keying
material PRK_4x3m and TH_4, or derived application keys, until the material PRK_4x3m and TH_4, or derived application keys, until the
Initiator is assured that the Responder has actually computed the key Initiator is assured that the Responder has actually computed the key
PRK_4x3m (explicit key confirmation). This is similar to waiting for PRK_4x3m (explicit key confirmation). This is similar to waiting for
acknowledgement (ACK) in a transport protocol. Explicit key acknowledgement (ACK) in a transport protocol. Explicit key
confirmation is e.g. assured when the Initiator has verified an confirmation is e.g. assured when the Initiator has verified an
OSCORE message or message_4 from the Responder. OSCORE message or message_4 from the Responder.
5.5.3. Responder Processing of Message 3 5.4.3. Responder Processing of Message 3
The Responder SHALL process message_3 as follows: The Responder SHALL process message_3 as follows:
* Decode message_3 (see Appendix B.1). o Decode message_3 (see Appendix C.1).
* Retrieve the protocol state using the connection identifier C_R o Retrieve the protocol state using the message correlation provided
and/or other external information such as the CoAP Token and the by the transport (e.g., the CoAP Token and the 5-tuple as a
5-tuple. client, or the prepended C_R as a server).
* Decrypt and verify the outer COSE_Encrypt0 as defined in o Decrypt and verify the outer COSE_Encrypt0 as defined in
Section 5.3 of [I-D.ietf-cose-rfc8152bis-struct], with the EDHOC Section 5.3 of [I-D.ietf-cose-rfc8152bis-struct], with the EDHOC
AEAD algorithm in the selected cipher suite, K_3ae, and IV_3ae. AEAD algorithm in the selected cipher suite, K_3ae, and IV_3ae.
* Pass EAD_3 to the security application. o Pass EAD_3 to the security application.
* Verify that the identity of the Initiator is an allowed identity o Verify that the identity of the Initiator is an allowed identity
for this connection, see Section 3.3. for this connection, see Section 3.5.
* Verify Signature_or_MAC_3 using the algorithm in the selected o Verify Signature_or_MAC_3 using the algorithm in the selected
cipher suite. The verification process depends on the method, see cipher suite. The verification process depends on the method, see
Section 5.5.2. Section 5.4.2.
* Pass the connection identifiers (C_I, C_R), and the application o Pass the connection identifiers (C_I, C_R), and the application
algorithms in the selected cipher suite to the security algorithms in the selected cipher suite to the security
application. The application can now derive application keys application. The application can now derive application keys
using the EDHOC-Exporter interface. using the EDHOC-Exporter interface.
If any processing step fails, the Responder SHOULD send an EDHOC If any processing step fails, the Responder SHOULD send an EDHOC
error message back, formatted as defined in Section 6. Sending error error message back, formatted as defined in Section 6. Sending error
messages is essential for debugging but MAY e.g.be skipped if a messages is essential for debugging but MAY e.g.be skipped if a
session cannot be found or due to denial of service reasons, see session cannot be found or due to denial of service reasons, see
Section 8. If an error message is sent, the session MUST be Section 7. If an error message is sent, the session MUST be
discontinued. discontinued.
After verifying message_3, the Responder is assured that the After verifying message_3, the Responder is assured that the
Initiator has calculated the key PRK_4x3m (explicit key confirmation) Initiator has calculated the key PRK_4x3m (explicit key confirmation)
and that no other party than the Responder can compute the key. The and that no other party than the Responder can compute the key. The
Responder can securely send protected application data and store the Responder can securely send protected application data and store the
keying material PRK_4x3m and TH_4. keying material PRK_4x3m and TH_4.
5.5. EDHOC Message 4
This section specifies message_4 which is OPTIONAL to support. Key
confirmation is normally provided by sending an application message
from the Responder to the Initiator protected with a key derived with
the EDHOC-Exporter, e.g., using OSCORE (see Appendix A). In
deployments where no protected application message is sent from the
Responder to the Initiator, the Responder MUST send message_4. Two
examples of such deployments:
1. When EDHOC is only used for authentication and no application
data is sent.
2. When application data is only sent from the Initiator to the
Responder.
Further considerations are provided in Section 3.9.
5.5.1. Formatting of Message 4
message_4 SHALL be a CBOR Sequence (see Appendix C.1) as defined
below
message_4 = (
CIPHERTEXT_4 : bstr,
)
5.5.2. Responder Processing of Message 4
The Responder SHALL compose message_4 as follows:
o Compute a COSE_Encrypt0 as defined in Section 5.3 of
[I-D.ietf-cose-rfc8152bis-struct], with the EDHOC AEAD algorithm
in the selected cipher suite, and the following parameters. The
protected header SHALL be empty.
* protected = h''
* external_aad = TH_4
* plaintext = ( ? EAD_4 )
where EAD_4 is protected external authorization data, see
Section 3.8. COSE constructs the input to the AEAD [RFC5116] as
follows:
* Key K = EDHOC-Exporter( "EDHOC_message_4_Key", h'', length )
* Nonce N = EDHOC-Exporter( "EDHOC_message_4_Nonce", h'', length
)
* Plaintext P = ( ? EAD_4 )
* Associated data A = [ "Encrypt0", h'', TH_4 ]
CIPHERTEXT_4 is the 'ciphertext' of the COSE_Encrypt0.
o Encode message_4 as a sequence of CBOR encoded data items as
specified in Section 5.5.1.
5.5.3. Initiator Processing of Message 4
The Initiator SHALL process message_4 as follows:
o Decode message_4 (see Appendix C.1).
o Retrieve the protocol state using the message correlation provided
by the transport (e.g., the CoAP Token and the 5-tuple as a
client, or the prepended C_I as a server).
o Decrypt and verify the outer COSE_Encrypt0 as defined in
Section 5.3 of [I-D.ietf-cose-rfc8152bis-struct], with the EDHOC
AEAD algorithm in the selected cipher suite, and the parameters
defined in Section 5.5.2.
o Pass EAD_4 to the security application.
If any verification step fails the Initiator MUST send an EDHOC error
message back, formatted as defined in Section 6, and the session MUST
be discontinued.
6. Error Handling 6. Error Handling
This section defines the format for error messages. This section defines the format for error messages.
An EDHOC error message can be sent by either endpoint as a reply to An EDHOC error message can be sent by either endpoint as a reply to
any non-error EDHOC message. How errors at the EDHOC layer are any non-error EDHOC message. How errors at the EDHOC layer are
transported depends on lower layers, which need to enable error transported depends on lower layers, which need to enable error
messages to be sent and processed as intended. messages to be sent and processed as intended.
Errors in EDHOC are fatal. After sending an error message, the Errors in EDHOC are fatal. After sending an error message, the
sender MUST discontinue the protocol. The receiver SHOULD treat an sender MUST discontinue the protocol. The receiver SHOULD treat an
error message as an indication that the other party likely has error message as an indication that the other party likely has
discontinued the protocol. But as the error message is not discontinued the protocol. But as the error message is not
authenticated, a received error message might also have been sent by authenticated, a received error message might also have been sent by
an attacker and the receiver MAY therefore try to continue the an attacker and the receiver MAY therefore try to continue the
protocol. protocol.
error SHALL be a CBOR Sequence (see Appendix B.1) as defined below error SHALL be a CBOR Sequence (see Appendix C.1) as defined below
error = ( error = (
? C_x : bstr_identifier,
ERR_CODE : int, ERR_CODE : int,
ERR_INFO : any ERR_INFO : any
) )
Figure 5: EDHOC Error Message Figure 5: EDHOC Error Message
where: where:
* C_x - (optional) variable length connection identifier, encoded as o ERR_CODE - error code encoded as an integer. The value 0 is used
a bstr_identifier (see Section 5.1). If error is sent by the
Responder and corr (METHOD_CORR mod 4) equals 0 or 2 then C_x is
set to C_I, else if error is sent by the Initiator and corr
(METHOD_CORR mod 4) equals 0 or 1 then C_x is set to C_R, else C_x
is omitted.
* ERR_CODE - error code encoded as an integer. The value 0 is used
for success, all other values (negative or positive) indicate for success, all other values (negative or positive) indicate
errors. errors.
* ERR_INFO - error information. Content and encoding depend on o ERR_INFO - error information. Content and encoding depend on
error code. error code.
The remainder of this section specifies the currently defined error The remainder of this section specifies the currently defined error
codes, see Figure 6. Error codes 1 and 2 MUST be supported. codes, see Figure 6. Error codes 1 and 2 MUST be supported.
Additional error codes and corresponding error information may be Additional error codes and corresponding error information may be
specified. specified.
+----------+---------------+----------------------------------------+ +----------+---------------+----------------------------------------+
| ERR_CODE | ERR_INFO Type | Description | | ERR_CODE | ERR_INFO Type | Description |
+==========+===============+========================================+ +==========+===============+========================================+
skipping to change at page 36, line 39 skipping to change at page 36, line 39
message is mainly intended for software engineers that during message is mainly intended for software engineers that during
debugging need to interpret it in the context of the EDHOC debugging need to interpret it in the context of the EDHOC
specification. The diagnostic message SHOULD be provided to the specification. The diagnostic message SHOULD be provided to the
calling application where it SHOULD be logged. calling application where it SHOULD be logged.
6.3. Wrong Selected Cipher Suite 6.3. Wrong Selected Cipher Suite
Error code 2 MUST only be used in a response to message_1 in case the Error code 2 MUST only be used in a response to message_1 in case the
cipher suite selected by the Initiator is not supported by the cipher suite selected by the Initiator is not supported by the
Responder, or if the Responder supports a cipher suite more preferred Responder, or if the Responder supports a cipher suite more preferred
by the Initiator than the selected cipher suite, see Section 5.3.3. by the Initiator than the selected cipher suite, see Section 5.2.3.
ERR_INFO is of type SUITES_R: ERR_INFO is of type SUITES_R:
SUITES_R : [ supported : 2* suite ] / suite SUITES_R : [ supported : 2* suite ] / suite
If the Responder does not support the selected cipher suite, then If the Responder does not support the selected cipher suite, then
SUITES_R MUST include one or more supported cipher suites. If the SUITES_R MUST include one or more supported cipher suites. If the
Responder does not support the selected cipher suite, but supports Responder does not support the selected cipher suite, but supports
another cipher suite in SUITES_I, then SUITES_R MUST include the another cipher suite in SUITES_I, then SUITES_R MUST include the
first supported cipher suite in SUITES_I. first supported cipher suite in SUITES_I.
skipping to change at page 37, line 31 skipping to change at page 37, line 31
Assume that the Initiator supports the five cipher suites 5, 6, 7, 8, Assume that the Initiator supports the five cipher suites 5, 6, 7, 8,
and 9 in decreasing order of preference. Figures 7 and 8 show and 9 in decreasing order of preference. Figures 7 and 8 show
examples of how the Initiator can truncate SUITES_I and how SUITES_R examples of how the Initiator can truncate SUITES_I and how SUITES_R
is used by Responders to give the Initiator information about the is used by Responders to give the Initiator information about the
cipher suites that the Responder supports. cipher suites that the Responder supports.
In the first example (Figure 7), the Responder supports cipher suite In the first example (Figure 7), the Responder supports cipher suite
6 but not the initially selected cipher suite 5. 6 but not the initially selected cipher suite 5.
Initiator Responder Initiator Responder
| METHOD_CORR, SUITES_I = 5, G_X, C_I, EAD_1 | | METHOD, SUITES_I = 5, G_X, C_I, EAD_1 |
+------------------------------------------------------------------>| +------------------------------------------------------------------>|
| message_1 | | message_1 |
| | | |
| C_I, DIAG_MSG, SUITES_R = 6 | | DIAG_MSG, SUITES_R = 6 |
|<------------------------------------------------------------------+ |<------------------------------------------------------------------+
| error | | error |
| | | |
| METHOD_CORR, SUITES_I = [6, 5, 6], G_X, C_I, EAD_1 | | METHOD, SUITES_I = [6, 5, 6], G_X, C_I, EAD_1 |
+------------------------------------------------------------------>| +------------------------------------------------------------------>|
| message_1 | | message_1 |
Figure 7: Example of Responder supporting suite 6 but not suite 5. Figure 7: Example of Responder supporting suite 6 but not suite 5.
In the second example (Figure 8), the Responder supports cipher In the second example (Figure 8), the Responder supports cipher
suites 8 and 9 but not the more preferred (by the Initiator) cipher suites 8 and 9 but not the more preferred (by the Initiator) cipher
suites 5, 6 or 7. To illustrate the negotiation mechanics we let the suites 5, 6 or 7. To illustrate the negotiation mechanics we let the
Initiator first make a guess that the Responder supports suite 6 but Initiator first make a guess that the Responder supports suite 6 but
not suite 5. Since the Responder supports neither 5 nor 6, it not suite 5. Since the Responder supports neither 5 nor 6, it
responds with an error and SUITES_R, after which the Initiator responds with an error and SUITES_R, after which the Initiator
selects its most preferred supported suite. The order of cipher selects its most preferred supported suite. The order of cipher
suites in SUITES_R does not matter. (If the Responder had supported suites in SUITES_R does not matter. (If the Responder had supported
suite 5, it would include it in SUITES_R of the response, and it suite 5, it would include it in SUITES_R of the response, and it
would in that case have become the selected suite in the second would in that case have become the selected suite in the second
message_1.) message_1.)
Initiator Responder Initiator Responder
| METHOD_CORR, SUITES_I = [6, 5, 6], G_X, C_I, EAD_1 | | METHOD, SUITES_I = [6, 5, 6], G_X, C_I, EAD_1 |
+------------------------------------------------------------------>| +------------------------------------------------------------------>|
| message_1 | | message_1 |
| | | |
| C_I, DIAG_MSG, SUITES_R = [9, 8] | | DIAG_MSG, SUITES_R = [9, 8] |
|<------------------------------------------------------------------+ |<------------------------------------------------------------------+
| error | | error |
| | | |
| METHOD_CORR, SUITES_I = [8, 5, 6, 7, 8], G_X, C_I, EAD_1 | | METHOD, SUITES_I = [8, 5, 6, 7, 8], G_X, C_I, EAD_1 |
+------------------------------------------------------------------>| +------------------------------------------------------------------>|
| message_1 | | message_1 |
Figure 8: Example of Responder supporting suites 8 and 9 but not Figure 8: Example of Responder supporting suites 8 and 9 but not 5, 6
5, 6 or 7. or 7.
Note that the Initiator's list of supported cipher suites and order Note that the Initiator's list of supported cipher suites and order
of preference is fixed (see Section 5.3.1 and Section 5.3.2). of preference is fixed (see Section 5.2.1 and Section 5.2.2).
Furthermore, the Responder shall only accept message_1 if the Furthermore, the Responder shall only accept message_1 if the
selected cipher suite is the first cipher suite in SUITES_I that the selected cipher suite is the first cipher suite in SUITES_I that the
Responder supports (see Section 5.3.3). Following this procedure Responder supports (see Section 5.2.3). Following this procedure
ensures that the selected cipher suite is the most preferred (by the ensures that the selected cipher suite is the most preferred (by the
Initiator) cipher suite supported by both parties. Initiator) cipher suite supported by both parties.
If the selected cipher suite is not the first cipher suite which the If the selected cipher suite is not the first cipher suite which the
Responder supports in SUITES_I received in message_1, then Responder Responder supports in SUITES_I received in message_1, then Responder
MUST discontinue the protocol, see Section 5.3.3. If SUITES_I in MUST discontinue the protocol, see Section 5.2.3. If SUITES_I in
message_1 is manipulated then the integrity verification of message_2 message_1 is manipulated then the integrity verification of message_2
containing the transcript hash TH_2 will fail and the Initiator will containing the transcript hash TH_2 will fail and the Initiator will
discontinue the protocol. discontinue the protocol.
7. Transferring EDHOC and Deriving an OSCORE Context 7. Security Considerations
7.1. EDHOC Message 4
This section specifies message_4 which is OPTIONAL to support. Key
confirmation is normally provided by sending an application message
from the Responder to the Initiator protected with a key derived with
the EDHOC-Exporter, e.g., using OSCORE (see
[I-D.ietf-core-oscore-edhoc]). In deployments where no protected
application message is sent from the Responder to the Initiator, the
Responder MUST send message_4. Two examples of such deployments:
1. When EDHOC is only used for authentication and no application
data is sent.
2. When application data is only sent from the Initiator to the
Responder.
Further considerations are provided in Section 3.7.
7.1.1. Formatting of Message 4
message_4 and data_4 SHALL be CBOR Sequences (see Appendix B.1) as
defined below
message_4 = (
data_4,
CIPHERTEXT_4 : bstr,
)
data_4 = (
? C_I : bstr_identifier,
)
7.1.2. Responder Processing of Message 4
The Responder SHALL compose message_4 as follows:
* If corr (METHOD_CORR mod 4) equals 1 or 3, C_I is omitted,
otherwise C_I is not omitted.
* Compute a COSE_Encrypt0 as defined in Section 5.3 of
[I-D.ietf-cose-rfc8152bis-struct], with the EDHOC AEAD algorithm
in the selected cipher suite, and the following parameters. The
protected header SHALL be empty.
- protected = h''
- external_aad = TH_4
- plaintext = ( ? EAD_4 )
where EAD_4 is protected external authorization data, see
Section 3.6. COSE constructs the input to the AEAD [RFC5116] as
follows:
- Key K = EDHOC-Exporter( "EDHOC_message_4_Key", length )
- Nonce N = EDHOC-Exporter( "EDHOC_message_4_Nonce", length )
- Plaintext P = ( ? EAD_4 )
- Associated data A = [ "Encrypt0", h'', TH_4 ]
CIPHERTEXT_4 is the 'ciphertext' of the COSE_Encrypt0.
* Encode message_4 as a sequence of CBOR encoded data items as
specified in Section 7.1.1.
7.1.3. Initiator Processing of Message 4
The Initiator SHALL process message_4 as follows:
* Decode message_4 (see Appendix B.1).
* Retrieve the protocol state using the connection identifier C_I
and/or other external information such as the CoAP Token and the
5-tuple.
* Decrypt and verify the outer COSE_Encrypt0 as defined in
Section 5.3 of [I-D.ietf-cose-rfc8152bis-struct], with the EDHOC
AEAD algorithm in the selected cipher suite, and the parameters
defined in Section 7.1.2.
* Pass EAD_4 to the security application.
If any verification step fails the Initiator MUST send an EDHOC error
message back, formatted as defined in Section 6, and the session MUST
be discontinued.
7.2. Transferring EDHOC in CoAP
It is recommended to transport EDHOC as an exchange of CoAP [RFC7252]
messages. CoAP is a reliable transport that can preserve packet
ordering and handle message duplication. CoAP can also perform
fragmentation and protect against denial of service attacks. It is
recommended to carry the EDHOC messages in Confirmable messages,
especially if fragmentation is used.
By default, the CoAP client is the Initiator and the CoAP server is
the Responder, but the roles SHOULD be chosen to protect the most
sensitive identity, see Section 8. By default, EDHOC is transferred
in POST requests and 2.04 (Changed) responses to the Uri-Path:
"/.well-known/edhoc", but an application may define its own path that
can be discovered e.g. using resource directory
[I-D.ietf-core-resource-directory].
By default, the message flow is as follows: EDHOC message_1 is sent
in the payload of a POST request from the client to the server's
resource for EDHOC. EDHOC message_2 or the EDHOC error message is
sent from the server to the client in the payload of a 2.04 (Changed)
response. EDHOC message_3 or the EDHOC error message is sent from
the client to the server's resource in the payload of a POST request.
If needed, an EDHOC error message is sent from the server to the
client in the payload of a 2.04 (Changed) response. Alternatively,
if EDHOC message_4 is used, it is sent from the server to the client
in the payload of a 2.04 (Changed) response analogously to message_2.
An example of a successful EDHOC exchange using CoAP is shown in
Figure 9. In this case the CoAP Token enables the Initiator to
correlate message_1 and message_2 so the correlation parameter corr =
1.
Client Server
| |
+--------->| Header: POST (Code=0.02)
| POST | Uri-Path: "/.well-known/edhoc"
| | Content-Format: application/edhoc
| | Payload: EDHOC message_1
| |
|<---------+ Header: 2.04 Changed
| 2.04 | Content-Format: application/edhoc
| | Payload: EDHOC message_2
| |
+--------->| Header: POST (Code=0.02)
| POST | Uri-Path: "/.well-known/edhoc"
| | Content-Format: application/edhoc
| | Payload: EDHOC message_3
| |
|<---------+ Header: 2.04 Changed
| 2.04 |
| |
Figure 9: Transferring EDHOC in CoAP when the Initiator is CoAP
Client
The exchange in Figure 9 protects the client identity against active
attackers and the server identity against passive attackers. An
alternative exchange that protects the server identity against active
attackers and the client identity against passive attackers is shown
in Figure 10. In this case the CoAP Token enables the Responder to
correlate message_2 and message_3 so the correlation parameter corr =
2. If EDHOC message_4 is used, it is transported with CoAP in the
payload of a POST request with a 2.04 (Changed) response.
Client Server
| |
+--------->| Header: POST (Code=0.02)
| POST | Uri-Path: "/.well-known/edhoc"
| |
|<---------+ Header: 2.04 Changed
| 2.04 | Content-Format: application/edhoc
| | Payload: EDHOC message_1
| |
+--------->| Header: POST (Code=0.02)
| POST | Uri-Path: "/.well-known/edhoc"
| | Content-Format: application/edhoc
| | Payload: EDHOC message_2
| |
|<---------+ Header: 2.04 Changed
| 2.04 | Content-Format: application/edhoc
| | Payload: EDHOC message_3
| |
Figure 10: Transferring EDHOC in CoAP when the Initiator is CoAP
Server
To protect against denial-of-service attacks, the CoAP server MAY
respond to the first POST request with a 4.01 (Unauthorized)
containing an Echo option [I-D.ietf-core-echo-request-tag]. This
forces the initiator to demonstrate its reachability at its apparent
network address. If message fragmentation is needed, the EDHOC
messages may be fragmented using the CoAP Block-Wise Transfer
mechanism [RFC7959]. EDHOC does not restrict how error messages are
transported with CoAP, as long as the appropriate error message can
to be transported in response to a message that failed (see
Section 6). The use of EDHOC with OSCORE is specified in
[I-D.ietf-core-oscore-edhoc].
8. Security Considerations
8.1. Security Properties 7.1. Security Properties
EDHOC inherits its security properties from the theoretical SIGMA-I EDHOC inherits its security properties from the theoretical SIGMA-I
protocol [SIGMA]. Using the terminology from [SIGMA], EDHOC provides protocol [SIGMA]. Using the terminology from [SIGMA], EDHOC provides
perfect forward secrecy, mutual authentication with aliveness, perfect forward secrecy, mutual authentication with aliveness,
consistency, and peer awareness. As described in [SIGMA], peer consistency, and peer awareness. As described in [SIGMA], peer
awareness is provided to the Responder, but not to the Initiator. awareness is provided to the Responder, but not to the Initiator.
EDHOC protects the credential identifier of the Initiator against EDHOC protects the credential identifier of the Initiator against
active attacks and the credential identifier of the Responder against active attacks and the credential identifier of the Responder against
passive attacks. The roles should be assigned to protect the most passive attacks. The roles should be assigned to protect the most
sensitive identity/identifier, typically that which is not possible sensitive identity/identifier, typically that which is not possible
to infer from routing information in the lower layers. to infer from routing information in the lower layers.
Compared to [SIGMA], EDHOC adds an explicit method type and expands Compared to [SIGMA], EDHOC adds an explicit method type and expands
the message authentication coverage to additional elements such as the message authentication coverage to additional elements such as
algorithms, external authorization data, and previous messages. This algorithms, external authorization data, and previous messages. This
protects against an attacker replaying messages or injecting messages protects against an attacker replaying messages or injecting messages
from another session. from another session.
EDHOC also adds negotiation of connection identifiers and downgrade EDHOC also adds selection of connection identifiers and downgrade
protected negotiation of cryptographic parameters, i.e. an attacker protected negotiation of cryptographic parameters, i.e. an attacker
cannot affect the negotiated parameters. A single session of EDHOC cannot affect the negotiated parameters. A single session of EDHOC
does not include negotiation of cipher suites, but it enables the does not include negotiation of cipher suites, but it enables the
Responder to verify that the selected cipher suite is the most Responder to verify that the selected cipher suite is the most
preferred cipher suite by the Initiator which is supported by both preferred cipher suite by the Initiator which is supported by both
the Initiator and the Responder. the Initiator and the Responder.
As required by [RFC7258], IETF protocols need to mitigate pervasive As required by [RFC7258], IETF protocols need to mitigate pervasive
monitoring when possible. One way to mitigate pervasive monitoring monitoring when possible. One way to mitigate pervasive monitoring
is to use a key exchange that provides perfect forward secrecy. is to use a key exchange that provides perfect forward secrecy.
skipping to change at page 45, line 5 skipping to change at page 40, line 45
run of the protocol by presenting the private ephemeral key, and vice run of the protocol by presenting the private ephemeral key, and vice
versa. Note that storing the private ephemeral keys violates the versa. Note that storing the private ephemeral keys violates the
protocol requirements. With static Diffie-Hellman key protocol requirements. With static Diffie-Hellman key
authentication, both parties can always deny having participated in authentication, both parties can always deny having participated in
the protocol. the protocol.
Two earlier versions of EDHOC have been formally analyzed [Norrman20] Two earlier versions of EDHOC have been formally analyzed [Norrman20]
[Bruni18] and the specification has been updated based on the [Bruni18] and the specification has been updated based on the
analysis. analysis.
8.2. Cryptographic Considerations 7.2. Cryptographic Considerations
The security of the SIGMA protocol requires the MAC to be bound to The security of the SIGMA protocol requires the MAC to be bound to
the identity of the signer. Hence the message authenticating the identity of the signer. Hence the message authenticating
functionality of the authenticated encryption in EDHOC is critical: functionality of the authenticated encryption in EDHOC is critical:
authenticated encryption MUST NOT be replaced by plain encryption authenticated encryption MUST NOT be replaced by plain encryption
only, even if authentication is provided at another level or through only, even if authentication is provided at another level or through
a different mechanism. EDHOC implements SIGMA-I using a MAC-then- a different mechanism. EDHOC implements SIGMA-I using a MAC-then-
Sign approach. Sign approach.
To reduce message overhead EDHOC does not use explicit nonces and To reduce message overhead EDHOC does not use explicit nonces and
skipping to change at page 46, line 5 skipping to change at page 41, line 41
parties can derive application keys with other labels or run EDHOC parties can derive application keys with other labels or run EDHOC
again. again.
Requirement for how to securely generate, validate, and process the Requirement for how to securely generate, validate, and process the
ephermeral public keys depend on the elliptic curve. For X25519 and ephermeral public keys depend on the elliptic curve. For X25519 and
X448, the requirements are defined in [RFC7748]. For secp256r1, X448, the requirements are defined in [RFC7748]. For secp256r1,
secp384r1, and secp521r1, the requirements are defined in Section 5 secp384r1, and secp521r1, the requirements are defined in Section 5
of [SP-800-56A]. For secp256r1, secp384r1, and secp521r1, at least of [SP-800-56A]. For secp256r1, secp384r1, and secp521r1, at least
partial public-key validation MUST be done. partial public-key validation MUST be done.
8.3. Cipher Suites and Cryptographic Algorithms 7.3. Cipher Suites and Cryptographic Algorithms
For many constrained IoT devices it is problematic to support more For many constrained IoT devices it is problematic to support more
than one cipher suite. Existing devices can be expected to support than one cipher suite. Existing devices can be expected to support
either ECDSA or EdDSA. To enable as much interoperability as we can either ECDSA or EdDSA. To enable as much interoperability as we can
reasonably achieve, less constrained devices SHOULD implement both reasonably achieve, less constrained devices SHOULD implement both
cipher suite 0 (AES-CCM-16-64-128, SHA-256, X25519, EdDSA, AES-CCM- cipher suite 0 (AES-CCM-16-64-128, SHA-256, X25519, EdDSA, AES-CCM-
16-64-128, SHA-256) and cipher suite 2 (AES-CCM-16-64-128, SHA-256, 16-64-128, SHA-256) and cipher suite 2 (AES-CCM-16-64-128, SHA-256,
P-256, ES256, AES-CCM-16-64-128, SHA-256). Constrained endpoints P-256, ES256, AES-CCM-16-64-128, SHA-256). Constrained endpoints
SHOULD implement cipher suite 0 or cipher suite 2. Implementations SHOULD implement cipher suite 0 or cipher suite 2. Implementations
only need to implement the algorithms needed for their supported only need to implement the algorithms needed for their supported
skipping to change at page 46, line 29 skipping to change at page 42, line 18
choice of key length used in the different algorithms needs to be choice of key length used in the different algorithms needs to be
harmonized, so that a sufficient security level is maintained for harmonized, so that a sufficient security level is maintained for
certificates, EDHOC, and the protection of application data. The certificates, EDHOC, and the protection of application data. The
Initiator and the Responder should enforce a minimum security level. Initiator and the Responder should enforce a minimum security level.
The hash algorithms SHA-1 and SHA-256/64 (256-bit Hash truncated to The hash algorithms SHA-1 and SHA-256/64 (256-bit Hash truncated to
64-bits) SHALL NOT be supported for use in EDHOC except for 64-bits) SHALL NOT be supported for use in EDHOC except for
certificate identification with x5u and c5u. Note that secp256k1 is certificate identification with x5u and c5u. Note that secp256k1 is
only defined for use with ECDSA and not for ECDH. only defined for use with ECDSA and not for ECDH.
8.4. Unprotected Data 7.4. Unprotected Data
The Initiator and the Responder must make sure that unprotected data The Initiator and the Responder must make sure that unprotected data
and metadata do not reveal any sensitive information. This also and metadata do not reveal any sensitive information. This also
applies for encrypted data sent to an unauthenticated party. In applies for encrypted data sent to an unauthenticated party. In
particular, it applies to EAD_1, ID_CRED_R, EAD_2, and error particular, it applies to EAD_1, ID_CRED_R, EAD_2, and error
messages. Using the same EAD_1 in several EDHOC sessions allows messages. Using the same EAD_1 in several EDHOC sessions allows
passive eavesdroppers to correlate the different sessions. Another passive eavesdroppers to correlate the different sessions. Another
consideration is that the list of supported cipher suites may consideration is that the list of supported cipher suites may
potentially be used to identify the application. potentially be used to identify the application.
The Initiator and the Responder must also make sure that The Initiator and the Responder must also make sure that
unauthenticated data does not trigger any harmful actions. In unauthenticated data does not trigger any harmful actions. In
particular, this applies to EAD_1 and error messages. particular, this applies to EAD_1 and error messages.
8.5. Denial-of-Service 7.5. Denial-of-Service
EDHOC itself does not provide countermeasures against Denial-of- EDHOC itself does not provide countermeasures against Denial-of-
Service attacks. By sending a number of new or replayed message_1 an Service attacks. By sending a number of new or replayed message_1 an
attacker may cause the Responder to allocate state, perform attacker may cause the Responder to allocate state, perform
cryptographic operations, and amplify messages. To mitigate such cryptographic operations, and amplify messages. To mitigate such
attacks, an implementation SHOULD rely on lower layer mechanisms such attacks, an implementation SHOULD rely on lower layer mechanisms such
as the Echo option in CoAP [I-D.ietf-core-echo-request-tag] that as the Echo option in CoAP [I-D.ietf-core-echo-request-tag] that
forces the initiator to demonstrate reachability at its apparent forces the initiator to demonstrate reachability at its apparent
network address. network address.
An attacker can also send faked message_2, message_3, message_4, or An attacker can also send faked message_2, message_3, message_4, or
error in an attempt to trick the receiving party to send an error error in an attempt to trick the receiving party to send an error
message and discontinue the session. EDHOC implementations MAY message and discontinue the session. EDHOC implementations MAY
evaluate if a received message is likely to have be forged by and evaluate if a received message is likely to have be forged by and
attacker and ignore it without sending an error message or attacker and ignore it without sending an error message or
discontinuing the session. discontinuing the session.
8.6. Implementation Considerations 7.6. Implementation Considerations
The availability of a secure random number generator is essential for The availability of a secure random number generator is essential for
the security of EDHOC. If no true random number generator is the security of EDHOC. If no true random number generator is
available, a truly random seed MUST be provided from an external available, a truly random seed MUST be provided from an external
source and used with a cryptographically secure pseudorandom number source and used with a cryptographically secure pseudorandom number
generator. As each pseudorandom number must only be used once, an generator. As each pseudorandom number must only be used once, an
implementation need to get a new truly random seed after reboot, or implementation need to get a new truly random seed after reboot, or
continuously store state in nonvolatile memory, see ([RFC8613], continuously store state in nonvolatile memory, see ([RFC8613],
Appendix B.1.1) for issues and solution approaches for writing to Appendix B.1.1) for issues and solution approaches for writing to
nonvolatile memory. Intentionally or unintentionally weak or nonvolatile memory. Intentionally or unintentionally weak or
skipping to change at page 49, line 12 skipping to change at page 44, line 42
outside that environment. Note that non-EDHOC code inside the TEE outside that environment. Note that non-EDHOC code inside the TEE
might still be able to read EDHOC data and tamper with EDHOC code, to might still be able to read EDHOC data and tamper with EDHOC code, to
protect against such attacks EDHOC needs to be in its own zone. To protect against such attacks EDHOC needs to be in its own zone. To
provide better protection against some forms of physical attacks, provide better protection against some forms of physical attacks,
sensitive EDHOC data should be stored inside the SoC or encrypted and sensitive EDHOC data should be stored inside the SoC or encrypted and
integrity protected when sent on a data bus (e.g. between the CPU and integrity protected when sent on a data bus (e.g. between the CPU and
RAM or Flash). Secure boot can be used to increase the security of RAM or Flash). Secure boot can be used to increase the security of
code and data in the Rich Execution Environment (REE) by validating code and data in the Rich Execution Environment (REE) by validating
the REE image. the REE image.
9. IANA Considerations 8. IANA Considerations
9.1. EDHOC Exporter Label 8.1. EDHOC Exporter Label
IANA has created a new registry titled "EDHOC Exporter Label" under IANA has created a new registry titled "EDHOC Exporter Label" under
the new heading "EDHOC". The registration procedure is "Expert the new heading "EDHOC". The registration procedure is "Expert
Review". The columns of the registry are Label, Description, and Review". The columns of the registry are Label, Description, and
Reference. All columns are text strings. The initial contents of Reference. All columns are text strings. The initial contents of
the registry are: the registry are:
Label: EDHOC_message_4_Key Label: EDHOC_message_4_Key
Description: Key used to protect EDHOC message_4 Description: Key used to protect EDHOC message_4
Reference: [[this document]] Reference: [[this document]]
Label: EDHOC_message_4_Nonce Label: EDHOC_message_4_Nonce
Description: Nonce used to protect EDHOC message_4 Description: Nonce used to protect EDHOC message_4
Reference: [[this document]] Reference: [[this document]]
9.2. EDHOC Cipher Suites Registry Label: OSCORE Master Secret
Description: Derived OSCORE Master Secret
Reference: [[this document]]
Label: OSCORE Master Salt
Description: Derived OSCORE Master Salt
Reference: [[this document]]
8.2. EDHOC Cipher Suites Registry
IANA has created a new registry titled "EDHOC Cipher Suites" under IANA has created a new registry titled "EDHOC Cipher Suites" under
the new heading "EDHOC". The registration procedure is "Expert the new heading "EDHOC". The registration procedure is "Expert
Review". The columns of the registry are Value, Array, Description, Review". The columns of the registry are Value, Array, Description,
and Reference, where Value is an integer and the other columns are and Reference, where Value is an integer and the other columns are
text strings. The initial contents of the registry are: text strings. The initial contents of the registry are:
Value: -24 Value: -24
Algorithms: N/A Algorithms: N/A
Desc: Reserved for Private Use Desc: Reserved for Private Use
skipping to change at page 50, line 34 skipping to change at page 46, line 29
AES-CCM-16-64-128, SHA-256 AES-CCM-16-64-128, SHA-256
Reference: [[this document]] Reference: [[this document]]
Value: 3 Value: 3
Array: 30, -16, 1, -7, 10, -16 Array: 30, -16, 1, -7, 10, -16
Desc: AES-CCM-16-128-128, SHA-256, P-256, ES256, Desc: AES-CCM-16-128-128, SHA-256, P-256, ES256,
AES-CCM-16-64-128, SHA-256 AES-CCM-16-64-128, SHA-256
Reference: [[this document]] Reference: [[this document]]
Value: 4 Value: 4
Array: 24, -16, 4, -8, 24, -16
Desc: ChaCha20/Poly1305, SHA-256, X25519, EdDSA,
ChaCha20/Poly1305, SHA-256
Reference: [[this document]]
Value: 5
Array: 24, -16, 1, -7, 24, -16
Desc: ChaCha20/Poly1305, SHA-256, P-256, ES256,
ChaCha20/Poly1305, SHA-256
Reference: [[this document]]
Value: 6
Array: 1, -16, 4, -7, 1, -16 Array: 1, -16, 4, -7, 1, -16
Desc: A128GCM, SHA-256, X25519, ES256, Desc: A128GCM, SHA-256, X25519, ES256,
A128GCM, SHA-256 A128GCM, SHA-256
Reference: [[this document]] Reference: [[this document]]
Value: 5 Value: 24
Array: 3, -43, 2, -35, 3, -43 Array: 3, -43, 2, -35, 3, -43
Desc: A256GCM, SHA-384, P-384, ES384, Desc: A256GCM, SHA-384, P-384, ES384,
A256GCM, SHA-384 A256GCM, SHA-384
Reference: [[this document]] Reference: [[this document]]
Value: 25
Array: 24, -45, 5, -8, 24, -45
Desc: ChaCha20/Poly1305, SHAKE256, X448, EdDSA,
ChaCha20/Poly1305, SHAKE256
Reference: [[this document]]
9.3. EDHOC Method Type Registry 8.3. EDHOC Method Type Registry
IANA has created a new registry entitled "EDHOC Method Type" under IANA has created a new registry entitled "EDHOC Method Type" under
the new heading "EDHOC". The registration procedure is "Expert the new heading "EDHOC". The registration procedure is "Expert
Review". The columns of the registry are Value, Description, and Review". The columns of the registry are Value, Description, and
Reference, where Value is an integer and the other columns are text Reference, where Value is an integer and the other columns are text
strings. The initial contents of the registry is shown in Figure 4. strings. The initial contents of the registry is shown in Figure 4.
9.4. EDHOC Error Codes Registry 8.4. EDHOC Error Codes Registry
IANA has created a new registry entitled "EDHOC Error Codes" under IANA has created a new registry entitled "EDHOC Error Codes" under
the new heading "EDHOC". The registration procedure is the new heading "EDHOC". The registration procedure is
"Specification Required". The columns of the registry are ERR_CODE, "Specification Required". The columns of the registry are ERR_CODE,
ERR_INFO Type and Description, where ERR_CODE is an integer, ERR_INFO ERR_INFO Type and Description, where ERR_CODE is an integer, ERR_INFO
is a CDDL defined type, and Description is a text string. The is a CDDL defined type, and Description is a text string. The
initial contents of the registry is shown in Figure 6. initial contents of the registry is shown in Figure 6.
9.5. The Well-Known URI Registry 8.5. COSE Header Parameters Registry
This document registers the following entries in the "COSE Header
Parameters" registry under the "CBOR Object Signing and Encryption
(COSE)" heading. The value of the 'cwt' header parameter is a CWT
[RFC8392] or an unprotected CWT Claims Set [I-D.ietf-rats-uccs].
+-----------+-------+----------------+------------------------------+
| Name | Label | Value Type | Description |
+===========+=======+================+==============================+
| cwt | TBD1 | COSE_Messages | A CBOR Web Token (CWT) or an |
| | | / map | unprotected CWT Claims Set |
+-----------+-------+----------------+------------------------------+
8.6. COSE Header Parameters Registry
IANA has added the COSE header parameter 'kid2' to the COSE Header
Parameters registry. The kid2 parameter may point to a COSE key
common parameter 'kid' or 'kid2'. The kid2 parameter can be used to
identify a key stored in a "raw" COSE_Key, in a CWT, or in a
certificate. The Value Reference for this item is empty and omitted
from the table below.
+------+-------+------------+----------------+-------------------+
| Name | Label | Value Type | Description | Reference |
+------+-------+------------+----------------+-------------------+
| kid2 | TBD | bstr / int | Key identifier | [[This document]] |
+------+-------+------------+----------------+-------------------+
8.7. COSE Key Common Parameters Registry
IANA has added the COSE key common parameter 'kid2' to the COSE Key
Common Parameters registry. The Value Reference for this item is
empty and omitted from the table below.
+------+-------+------------+----------------+-------------------+
| Name | Label | Value Type | Description | Reference |
+------+-------+------------+----------------+-------------------+
| kid2 | TBD | bstr / int | Key identifi- | [[This document]] |
| | | | cation value - | |
| | | | match to kid2 | |
| | | | in message | |
+------+-------+------------+----------------+-------------------+
8.8. The Well-Known URI Registry
IANA has added the well-known URI 'edhoc' to the Well-Known URIs IANA has added the well-known URI 'edhoc' to the Well-Known URIs
registry. registry.
* URI suffix: edhoc o URI suffix: edhoc
* Change controller: IETF o Change controller: IETF
* Specification document(s): [[this document]] o Specification document(s): [[this document]]
* Related information: None o Related information: None
9.6. Media Types Registry 8.9. Media Types Registry
IANA has added the media type 'application/edhoc' to the Media Types IANA has added the media type 'application/edhoc' to the Media Types
registry. registry.
* Type name: application o Type name: application
* Subtype name: edhoc
* Required parameters: N/A o Subtype name: edhoc
* Optional parameters: N/A o Required parameters: N/A
* Encoding considerations: binary o Optional parameters: N/A
* Security considerations: See Section 7 of this document. o Encoding considerations: binary
o Security considerations: See Section 7 of this document.
* Interoperability considerations: N/A o Interoperability considerations: N/A
* Published specification: [[this document]] (this document) o Published specification: [[this document]] (this document)
* Applications that use this media type: To be identified o Applications that use this media type: To be identified
* Fragment identifier considerations: N/A o Fragment identifier considerations: N/A
* Additional information: o Additional information:
- Magic number(s): N/A * Magic number(s): N/A
- File extension(s): N/A * File extension(s): N/A
- Macintosh file type code(s): N/A * Macintosh file type code(s): N/A
* Person & email address to contact for further information: See o Person & email address to contact for further information: See
"Authors' Addresses" section. "Authors' Addresses" section.
* Intended usage: COMMON o Intended usage: COMMON
* Restrictions on usage: N/A o Restrictions on usage: N/A
* Author: See "Authors' Addresses" section. o Author: See "Authors' Addresses" section.
* Change Controller: IESG o Change Controller: IESG
9.7. CoAP Content-Formats Registry 8.10. CoAP Content-Formats Registry
IANA has added the media type 'application/edhoc' to the CoAP IANA has added the media type 'application/edhoc' to the CoAP
Content-Formats registry. Content-Formats registry.
* Media Type: application/edhoc o Media Type: application/edhoc
* Encoding: o Encoding:
* ID: TBD42 o ID: TBD42
* Reference: [[this document]] o Reference: [[this document]]
9.8. Expert Review Instructions 8.11. EDHOC External Authorization Data
IANA has created a new registry entitled "EDHOC External
Authorization Data" under the new heading "EDHOC". The registration
procedure is "Expert Review". The columns of the registry are Value,
Description, and Reference, where Value is an integer and the other
columns are text strings.
8.12. Expert Review Instructions
The IANA Registries established in this document is defined as The IANA Registries established in this document is defined as
"Expert Review". This section gives some general guidelines for what "Expert Review". This section gives some general guidelines for what
the experts should be looking for, but they are being designated as the experts should be looking for, but they are being designated as
experts for a reason so they should be given substantial latitude. experts for a reason so they should be given substantial latitude.
Expert reviewers should take into consideration the following points: Expert reviewers should take into consideration the following points:
* Clarity and correctness of registrations. Experts are expected to o Clarity and correctness of registrations. Experts are expected to
check the clarity of purpose and use of the requested entries. check the clarity of purpose and use of the requested entries.
Expert needs to make sure the values of algorithms are taken from Expert needs to make sure the values of algorithms are taken from
the right registry, when that's required. Expert should consider the right registry, when that's required. Expert should consider
requesting an opinion on the correctness of registered parameters requesting an opinion on the correctness of registered parameters
from relevant IETF working groups. Encodings that do not meet from relevant IETF working groups. Encodings that do not meet
these objective of clarity and completeness should not be these objective of clarity and completeness should not be
registered. registered.
* Experts should take into account the expected usage of fields when o Experts should take into account the expected usage of fields when
approving point assignment. The length of the encoded value approving point assignment. The length of the encoded value
should be weighed against how many code points of that length are should be weighed against how many code points of that length are
left, the size of device it will be used on, and the number of left, the size of device it will be used on, and the number of
code points left that encode to that size. code points left that encode to that size.
* Specifications are recommended. When specifications are not o Specifications are recommended. When specifications are not
provided, the description provided needs to have sufficient provided, the description provided needs to have sufficient
information to verify the points above. information to verify the points above.
10. References 9. References
10.1. Normative References 9.1. Normative References
[I-D.ietf-core-echo-request-tag]
Amsuess, C., Mattsson, J. P., and G. Selander, "CoAP:
Echo, Request-Tag, and Token Processing", draft-ietf-core-
echo-request-tag-12 (work in progress), February 2021.
[I-D.ietf-cose-rfc8152bis-algs]
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", draft-ietf-cose-rfc8152bis-algs-12
(work in progress), September 2020.
[I-D.ietf-cose-rfc8152bis-struct]
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", draft-ietf-cose-rfc8152bis-
struct-15 (work in progress), February 2021.
[I-D.ietf-cose-x509]
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Header parameters for carrying and referencing X.509
certificates", draft-ietf-cose-x509-08 (work in progress),
December 2020.
[I-D.ietf-lake-reqs]
Vucinic, M., Selander, G., Mattsson, J. P., and D. Garcia-
Carrillo, "Requirements for a Lightweight AKE for OSCORE",
draft-ietf-lake-reqs-04 (work in progress), June 2020.
[I-D.ietf-rats-uccs]
Birkholz, H., O'Donoghue, J., Cam-Winget, N., and C.
Bormann, "A CBOR Tag for Unprotected CWT Claims Sets",
draft-ietf-rats-uccs-00 (work in progress), May 2021.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
<https://www.rfc-editor.org/info/rfc5116>. <https://www.rfc-editor.org/info/rfc5116>.
skipping to change at page 54, line 5 skipping to change at page 52, line 14
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014, DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>. <https://www.rfc-editor.org/info/rfc7252>.
[RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves [RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
for Security", RFC 7748, DOI 10.17487/RFC7748, January for Security", RFC 7748, DOI 10.17487/RFC7748, January
2016, <https://www.rfc-editor.org/info/rfc7748>. 2016, <https://www.rfc-editor.org/info/rfc7748>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>.
[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in [RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959, the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016, DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/info/rfc7959>. <https://www.rfc-editor.org/info/rfc7959>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8376] Farrell, S., Ed., "Low-Power Wide Area Network (LPWAN) [RFC8376] Farrell, S., Ed., "Low-Power Wide Area Network (LPWAN)
Overview", RFC 8376, DOI 10.17487/RFC8376, May 2018, Overview", RFC 8376, DOI 10.17487/RFC8376, May 2018,
<https://www.rfc-editor.org/info/rfc8376>. <https://www.rfc-editor.org/info/rfc8376>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/info/rfc8392>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/info/rfc8610>. June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[RFC8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz, [RFC8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments "Object Security for Constrained RESTful Environments
(OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019, (OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,
<https://www.rfc-editor.org/info/rfc8613>. <https://www.rfc-editor.org/info/rfc8613>.
[RFC8724] Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC. [RFC8724] Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC.
Zúñiga, "SCHC: Generic Framework for Static Context Header Zuniga, "SCHC: Generic Framework for Static Context Header
Compression and Fragmentation", RFC 8724, Compression and Fragmentation", RFC 8724,
DOI 10.17487/RFC8724, April 2020, DOI 10.17487/RFC8724, April 2020,
<https://www.rfc-editor.org/info/rfc8724>. <https://www.rfc-editor.org/info/rfc8724>.
[RFC8742] Bormann, C., "Concise Binary Object Representation (CBOR) [RFC8742] Bormann, C., "Concise Binary Object Representation (CBOR)
Sequences", RFC 8742, DOI 10.17487/RFC8742, February 2020, Sequences", RFC 8742, DOI 10.17487/RFC8742, February 2020,
<https://www.rfc-editor.org/info/rfc8742>. <https://www.rfc-editor.org/info/rfc8742>.
[I-D.ietf-cose-rfc8152bis-struct] [RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Schaad, J., "CBOR Object Signing and Encryption (COSE): Representation (CBOR)", STD 94, RFC 8949,
Structures and Process", Work in Progress, Internet-Draft, DOI 10.17487/RFC8949, December 2020,
draft-ietf-cose-rfc8152bis-struct-15, 1 February 2021, <https://www.rfc-editor.org/info/rfc8949>.
<https://www.ietf.org/archive/id/draft-ietf-cose-
rfc8152bis-struct-15.txt>.
[I-D.ietf-cose-rfc8152bis-algs] 9.2. Informative References
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", Work in Progress, Internet-Draft,
draft-ietf-cose-rfc8152bis-algs-12, 24 September 2020,
<https://www.ietf.org/archive/id/draft-ietf-cose-
rfc8152bis-algs-12.txt>.
[I-D.ietf-cose-x509] [Bruni18] Bruni, A., Sahl Joergensen, T., Groenbech Petersen, T.,
Schaad, J., "CBOR Object Signing and Encryption (COSE): and C. Schuermann, "Formal Verification of Ephemeral
Header parameters for carrying and referencing X.509 Diffie-Hellman Over COSE (EDHOC)", November 2018,
certificates", Work in Progress, Internet-Draft, draft- <https://www.springerprofessional.de/en/formal-
ietf-cose-x509-08, 14 December 2020, verification-of-ephemeral-diffie-hellman-over-cose-
<https://www.ietf.org/internet-drafts/draft-ietf-cose- edhoc/16284348>.
x509-08.txt>.
[I-D.ietf-core-echo-request-tag] [CborMe] Bormann, C., "CBOR Playground", May 2018,
Amsüss, C., Mattsson, J. P., and G. Selander, "CoAP: Echo, <http://cbor.me/>.
Request-Tag, and Token Processing", Work in Progress,
Internet-Draft, draft-ietf-core-echo-request-tag-12, 1
February 2021, <https://www.ietf.org/archive/id/draft-
ietf-core-echo-request-tag-12.txt>.
[I-D.ietf-lake-reqs] [CNSA] (Placeholder), ., "Commercial National Security Algorithm
Vucinic, M., Selander, G., Mattsson, J. P., and D. Garcia- Suite", August 2015,
Carrillo, "Requirements for a Lightweight AKE for OSCORE", <https://apps.nsa.gov/iaarchive/programs/iad-initiatives/
Work in Progress, Internet-Draft, draft-ietf-lake-reqs-04, cnsa-suite.cfm>.
8 June 2020, <https://www.ietf.org/archive/id/draft-ietf-
lake-reqs-04.txt>.
10.2. Informative References [I-D.ietf-core-oscore-edhoc]
Palombini, F., Tiloca, M., Hoeglund, R., Hristozov, S.,
and G. Selander, "Combining EDHOC and OSCORE", draft-ietf-
core-oscore-edhoc-00 (work in progress), April 2021.
[I-D.ietf-core-resource-directory]
Amsuess, C., Shelby, Z., Koster, M., Bormann, C., and P.
V. D. Stok, "CoRE Resource Directory", draft-ietf-core-
resource-directory-28 (work in progress), March 2021.
[I-D.ietf-cose-cbor-encoded-cert]
Raza, S., Hoeglund, J., Selander, G., Mattsson, J. P., and
M. Furuhed, "CBOR Encoded X.509 Certificates (C509
Certificates)", draft-ietf-cose-cbor-encoded-cert-00 (work
in progress), April 2021.
[I-D.ietf-lwig-security-protocol-comparison]
Mattsson, J. P., Palombini, F., and M. Vucinic,
"Comparison of CoAP Security Protocols", draft-ietf-lwig-
security-protocol-comparison-05 (work in progress),
November 2020.
[I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", draft-ietf-tls-dtls13-43 (work in progress), April
2021.
[I-D.mattsson-cfrg-det-sigs-with-noise]
Mattsson, J. P., Thormarker, E., and S. Ruohomaa,
"Deterministic ECDSA and EdDSA Signatures with Additional
Randomness", draft-mattsson-cfrg-det-sigs-with-noise-02
(work in progress), March 2020.
[I-D.selander-ace-ake-authz]
Selander, G., Mattsson, J. P., Vucinic, M., Richardson,
M., and A. Schellenbaum, "Lightweight Authorization for
Authenticated Key Exchange.", draft-selander-ace-ake-
authz-02 (work in progress), November 2020.
[Norrman20]
Norrman, K., Sundararajan, V., and A. Bruni, "Formal
Analysis of EDHOC Key Establishment for Constrained IoT
Devices", September 2020,
<https://arxiv.org/abs/2007.11427>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228, Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014, DOI 10.17487/RFC7228, May 2014,
<https://www.rfc-editor.org/info/rfc7228>. <https://www.rfc-editor.org/info/rfc7228>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <https://www.rfc-editor.org/info/rfc7258>. 2014, <https://www.rfc-editor.org/info/rfc7258>.
skipping to change at page 56, line 10 skipping to change at page 55, line 5
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>. <https://www.rfc-editor.org/info/rfc8446>.
[RFC8937] Cremers, C., Garratt, L., Smyshlyaev, S., Sullivan, N., [RFC8937] Cremers, C., Garratt, L., Smyshlyaev, S., Sullivan, N.,
and C. Wood, "Randomness Improvements for Security and C. Wood, "Randomness Improvements for Security
Protocols", RFC 8937, DOI 10.17487/RFC8937, October 2020, Protocols", RFC 8937, DOI 10.17487/RFC8937, October 2020,
<https://www.rfc-editor.org/info/rfc8937>. <https://www.rfc-editor.org/info/rfc8937>.
[I-D.ietf-core-resource-directory] [SECG] "Standards for Efficient Cryptography 1 (SEC 1)", May
Amsüss, C., Shelby, Z., Koster, M., Bormann, C., and P. V. 2009, <https://www.secg.org/sec1-v2.pdf>.
D. Stok, "CoRE Resource Directory", Work in Progress,
Internet-Draft, draft-ietf-core-resource-directory-28, 7
March 2021, <https://www.ietf.org/archive/id/draft-ietf-
core-resource-directory-28.txt>.
[I-D.ietf-lwig-security-protocol-comparison]
Mattsson, J. P., Palombini, F., and M. Vucinic,
"Comparison of CoAP Security Protocols", Work in Progress,
Internet-Draft, draft-ietf-lwig-security-protocol-
comparison-05, 2 November 2020,
<https://www.ietf.org/archive/id/draft-ietf-lwig-security-
protocol-comparison-05.txt>.
[I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", Work in Progress, Internet-Draft, draft-ietf-tls-
dtls13-43, 30 April 2021, <https://www.ietf.org/internet-
drafts/draft-ietf-tls-dtls13-43.txt>.
[I-D.selander-ace-ake-authz]
Selander, G., Mattsson, J. P., Vucinic, M., Richardson,
M., and A. Schellenbaum, "Lightweight Authorization for
Authenticated Key Exchange.", Work in Progress, Internet-
Draft, draft-selander-ace-ake-authz-02, 2 November 2020,
<https://www.ietf.org/archive/id/draft-selander-ace-ake-
authz-02.txt>.
[I-D.ietf-core-oscore-edhoc]
Palombini, F., Tiloca, M., Hoeglund, R., Hristozov, S.,
and G. Selander, "Combining EDHOC and OSCORE", Work in
Progress, Internet-Draft, draft-ietf-core-oscore-edhoc-00,
1 April 2021, <https://www.ietf.org/internet-drafts/draft-
ietf-core-oscore-edhoc-00.txt>.
[I-D.ietf-cose-cbor-encoded-cert]
Raza, S., Höglund, J., Selander, G., Mattsson, J. P., and
M. Furuhed, "CBOR Encoded X.509 Certificates (C509
Certificates)", Work in Progress, Internet-Draft, draft-
ietf-cose-cbor-encoded-cert-00, 28 April 2021,
<https://www.ietf.org/archive/id/draft-ietf-cose-cbor-
encoded-cert-00.txt>.
[I-D.mattsson-cfrg-det-sigs-with-noise] [SIGMA] Krawczyk, H., "SIGMA - The 'SIGn-and-MAc' Approach to
Mattsson, J. P., Thormarker, E., and S. Ruohomaa, Authenticated Diffie-Hellman and Its Use in the IKE-
"Deterministic ECDSA and EdDSA Signatures with Additional Protocols (Long version)", June 2003,
Randomness", Work in Progress, Internet-Draft, draft- <http://webee.technion.ac.il/~hugo/sigma-pdf.pdf>.
mattsson-cfrg-det-sigs-with-noise-02, 11 March 2020,
<https://www.ietf.org/archive/id/draft-mattsson-cfrg-det-
sigs-with-noise-02.txt>.
[SP-800-56A] [SP-800-56A]
Barker, E., Chen, L., Roginsky, A., Vassilev, A., and R. Barker, E., Chen, L., Roginsky, A., Vassilev, A., and R.
Davis, "Recommendation for Pair-Wise Key-Establishment Davis, "Recommendation for Pair-Wise Key-Establishment
Schemes Using Discrete Logarithm Cryptography", Schemes Using Discrete Logarithm Cryptography",
NIST Special Publication 800-56A Revision 3, April 2018, NIST Special Publication 800-56A Revision 3, April 2018,
<https://doi.org/10.6028/NIST.SP.800-56Ar3>. <https://doi.org/10.6028/NIST.SP.800-56Ar3>.
[SECG] "Standards for Efficient Cryptography 1 (SEC 1)", May Appendix A. Use with OSCORE and Transfer over CoAP
2009, <https://www.secg.org/sec1-v2.pdf>.
[SIGMA] Krawczyk, H., "SIGMA - The 'SIGn-and-MAc' Approach to This sppendix describes how to select EDHOC connection identifiers
Authenticated Diffie-Hellman and Its Use in the IKE- and derive an OSCORE security context when OSCORE is used with EDHOC,
Protocols (Long version)", June 2003, and how to transfer EDHOC messages over CoAP.
<http://webee.technion.ac.il/~hugo/sigma-pdf.pdf>.
[CNSA] (Placeholder), ., "Commercial National Security Algorithm A.1. Selecting EDHOC Connection Identifier
Suite", August 2015,
<https://apps.nsa.gov/iaarchive/programs/iad-initiatives/
cnsa-suite.cfm>.
[Norrman20] This section specifies a rule for converting from EDHOC connection
Norrman, K., Sundararajan, V., and A. Bruni, "Formal identifier to OSCORE Sender/Recipient ID. (An identifier is Sender
Analysis of EDHOC Key Establishment for Constrained IoT ID or Recipient ID depending on from which endpoint is the point of
Devices", September 2020, view, see Section 3.1 of [RFC8613].)
<https://arxiv.org/abs/2007.11427>.
[Bruni18] Bruni, A., Sahl Jørgensen, T., Grønbech Petersen, T., and o If the EDHOC connection identifier is numeric, i.e. encoded as a
C. Schürmann, "Formal Verification of Ephemeral Diffie- CBOR integer on the wire, it is converted to a (naturally byte-
Hellman Over COSE (EDHOC)", November 2018, string shaped) OSCORE Sender/Recipient ID equal to its CBOR
<https://www.springerprofessional.de/en/formal- encoded form.
verification-of-ephemeral-diffie-hellman-over-cose-
edhoc/16284348>.
[CborMe] Bormann, C., "CBOR Playground", May 2018, For example, a numeric C_R equal to 10 (0x0A in CBOR encoding) is
<http://cbor.me/>. converted to a (typically client) Sender ID equal to 0x0A, while a
numeric C_I equal to -12 (0x2B in CBOR encoding) is converted to a
(typically client) Sender ID equal to 0x2B.
Appendix A. Compact Representation o If the EDHOC connection identifier is byte-valued, hence encoded
as a CBOR byte string on the wire, it is converted to an OSCORE
Sender/Recipient ID equal to the byte string.
For example, a byte-string valued C_R equal to 0xFF (0x41FF in CBOR
encoding) is converted to a (typically client) Sender ID equal to
0xFF.
Two EDHOC connection identifiers are called "equivalent" if and only
if, by applying the conversion above, they both result in the same
OSCORE Sender/Recipient ID. For example, the two EDHOC connection
identifiers with CBOR encoding 0x0A (numeric) and 0x410A (byte-
valued) are equivalent since they both result in the same OSCORE
Sender/Recipient ID 0x0A.
When EDHOC is used to establish an OSCORE security context, the
connection identifiers C_I and C_R MUST NOT be equivalent.
Furthermore, in case of multiple OSCORE security contexts with
potentially different endpoints, to facilitate retrieval of the
correct OSCORE security context, an endpoint SHOULD select an EDHOC
connection identifier that when converted to OSCORE Recipient ID does
not coincide with its other Recipient IDs.
A.2. Deriving the OSCORE Security Context
This section specifies how to use EDHOC output to derive the OSCORE
security context.
After successful processing of EDHOC message_3, Client and Server
derive Security Context parameters for OSCORE as follows (see
Section 3.2 of [RFC8613]):
o The Master Secret and Master Salt are derived by using the EDHOC-
Exporter interface, see Section 4.1.
The EDHOC Exporter Labels for deriving the OSCORE Master Secret and
the OSCORE Master Salt, are "OSCORE Master Secret" and "OSCORE Master
Salt", respectively.
The context parameter is h'' (0x40), the empty CBOR byte string.
By default, key_length is the key length (in bytes) of the
application AEAD Algorithm of the selected cipher suite for the EDHOC
session. Also by default, salt_length has value 8. The Initiator
and Responder MAY agree out-of-band on a longer key_length than the
default and on a different salt_length.
Master Secret = EDHOC-Exporter( "OSCORE Master Secret", h'', key_length )
Master Salt = EDHOC-Exporter( "OSCORE Master Salt", h'', salt_length )
o The AEAD Algorithm is the application AEAD algorithm of the
selected cipher suite for the EDHOC session.
o The HKDF Algorithm is the one based on the application hash
algorithm of the selected cipher suite for the EDHOC session. For
example, if SHA-256 is the application hash algorithm of the
selected ciphersuite, HKDF SHA-256 is used as HKDF Algorithm in
the OSCORE Security Context.
o In case the Client is Initiator and the Server is Responder, the
Client's OSCORE Sender ID and the Server's OSCORE Sender ID are
determined from the EDHOC connection identifiers C_R and C_I for
the EDHOC session, respectively, by applying the conversion in
Appendix A.1. The reverse applies in case the Client is the
Responder and the Server is the Initiator.
Client and Server use the parameters above to establish an OSCORE
Security Context, as per Section 3.2.1 of [RFC8613].
From then on, Client and Server retrieve the OSCORE protocol state
using the Recipient ID, and optionally other transport information
such as the 5-tuple.
A.3. Transferring EDHOC over CoAP
This section specifies one instance for how EDHOC can be transferred
as an exchange of CoAP [RFC7252] messages. CoAP is a reliable
transport that can preserve packet ordering and handle message
duplication. CoAP can also perform fragmentation and protect against
denial of service attacks. According to this specification, EDHOC
messages are carried in Confirmable messages, which is beneficial
especially if fragmentation is used.
By default, the CoAP client is the Initiator and the CoAP server is
the Responder, but the roles SHOULD be chosen to protect the most
sensitive identity, see Section 7. According to this specification,
EDHOC is transferred in POST requests and 2.04 (Changed) responses to
the Uri-Path: "/.well-known/edhoc". An application may define its
own path that can be discovered, e.g., using resource directory
[I-D.ietf-core-resource-directory].
By default, the message flow is as follows: EDHOC message_1 is sent
in the payload of a POST request from the client to the server's
resource for EDHOC. EDHOC message_2 or the EDHOC error message is
sent from the server to the client in the payload of a 2.04 (Changed)
response. EDHOC message_3 or the EDHOC error message is sent from
the client to the server's resource in the payload of a POST request.
If needed, an EDHOC error message is sent from the server to the
client in the payload of a 2.04 (Changed) response. Alternatively,
if EDHOC message_4 is used, it is sent from the server to the client
in the payload of a 2.04 (Changed) response analogously to message_2.
In order to correlate a message received from a client to a message
previously sent by the server, messages sent by the client are
prepended with the CBOR serialization of the connection identifier
which the server has chosen. This applies independently of if the
CoAP server is Responder or Initiator. For the default case when the
server is Responder, the prepended connection identifier is C_R, and
C_I if the server is Initiator. If message_1 is sent to the server,
the CBOR simple value "null" (0xf6) is sent in its place (given that
the server has not selected C_R yet).
These identifiers are encoded in CBOR and thus self-delimiting. They
are sent in front of the actual EDHOC message, and only the part of
the body following the identifier is used for EDHOC processing.
Consequently, the application/edhoc media type does not apply to
these messages; their media type is unnamed.
An example of a successful EDHOC exchange using CoAP is shown in
Figure 9. In this case the CoAP Token enables correlation on the
Initiator side, and the prepended C_R enables correlation on the
Responder (server) side.
Client Server
| |
+--------->| Header: POST (Code=0.02)
| POST | Uri-Path: "/.well-known/edhoc"
| | Payload: null, EDHOC message_1
| |
|<---------+ Header: 2.04 Changed
| 2.04 | Content-Format: application/edhoc
| | Payload: EDHOC message_2
| |
+--------->| Header: POST (Code=0.02)
| POST | Uri-Path: "/.well-known/edhoc"
| | Payload: C_R, EDHOC message_3
| |
|<---------+ Header: 2.04 Changed
| 2.04 |
| |
Figure 9: Transferring EDHOC in CoAP when the Initiator is CoAP
Client
The exchange in Figure 9 protects the client identity against active
attackers and the server identity against passive attackers.
An alternative exchange that protects the server identity against
active attackers and the client identity against passive attackers is
shown in Figure 10. In this case the CoAP Token enables the
Responder to correlate message_2 and message_3, and the prepended C_I
enables correlation on the Initiator (server) side. If EDHOC
message_4 is used, C_I is prepended, and it is transported with CoAP
in the payload of a POST request with a 2.04 (Changed) response.
Client Server
| |
+--------->| Header: POST (Code=0.02)
| POST | Uri-Path: "/.well-known/edhoc"
| |
|<---------+ Header: 2.04 Changed
| 2.04 | Content-Format: application/edhoc
| | Payload: EDHOC message_1
| |
+--------->| Header: POST (Code=0.02)
| POST | Uri-Path: "/.well-known/edhoc"
| | Payload: C_I, EDHOC message_2
| |
|<---------+ Header: 2.04 Changed
| 2.04 | Content-Format: application/edhoc
| | Payload: EDHOC message_3
| |
Figure 10: Transferring EDHOC in CoAP when the Initiator is CoAP
Server
To protect against denial-of-service attacks, the CoAP server MAY
respond to the first POST request with a 4.01 (Unauthorized)
containing an Echo option [I-D.ietf-core-echo-request-tag]. This
forces the initiator to demonstrate its reachability at its apparent
network address. If message fragmentation is needed, the EDHOC
messages may be fragmented using the CoAP Block-Wise Transfer
mechanism [RFC7959]. EDHOC does not restrict how error messages are
transported with CoAP, as long as the appropriate error message can
to be transported in response to a message that failed (see
Section 6).
A.3.1. Transferring EDHOC and OSCORE over CoAP
A method for combining EDHOC and OSCORE protocols in two round-trips
is specified in [I-D.ietf-core-oscore-edhoc].
When using EDHOC over CoAP for establishing an OSCORE Security
Context, EDHOC error messages sent as CoAP responses MUST be error
responses, i.e., they MUST specify a CoAP error response code. In
particular, it is RECOMMENDED that such error responses have response
code either 4.00 (Bad Request) in case of client error (e.g., due to
a malformed EDHOC message), or 5.00 (Internal Server Error) in case
of server error (e.g., due to failure in deriving EDHOC key
material).
Appendix B. Compact Representation
As described in Section 4.2 of [RFC6090] the x-coordinate of an As described in Section 4.2 of [RFC6090] the x-coordinate of an
elliptic curve public key is a suitable representative for the entire elliptic curve public key is a suitable representative for the entire
point whenever scalar multiplication is used as a one-way function. point whenever scalar multiplication is used as a one-way function.
One example is ECDH with compact output, where only the x-coordinate One example is ECDH with compact output, where only the x-coordinate
of the computed value is used as the shared secret. of the computed value is used as the shared secret.
This section defines a format for compact representation based on the This section defines a format for compact representation based on the
Elliptic-Curve-Point-to-Octet-String Conversion defined in Elliptic-Curve-Point-to-Octet-String Conversion defined in
Section 2.3.3 of [SECG]. Using the notation from [SECG], the output Section 2.3.3 of [SECG]. Using the notation from [SECG], the output
skipping to change at page 58, line 44 skipping to change at page 60, line 41
format by prepending it with the single byte 0x02 (i.e. M = 0x02 || format by prepending it with the single byte 0x02 (i.e. M = 0x02 ||
X). X).
Using compact representation have some security benefits. An Using compact representation have some security benefits. An
implementation does not need to check that the point is not the point implementation does not need to check that the point is not the point
at infinity (the identity element). Similarly, as not even the sign at infinity (the identity element). Similarly, as not even the sign
of the y-coordinate is encoded, compact representation trivially of the y-coordinate is encoded, compact representation trivially
avoids so called "benign malleability" attacks where an attacker avoids so called "benign malleability" attacks where an attacker
changes the sign, see [SECG]. changes the sign, see [SECG].
Appendix B. Use of CBOR, CDDL and COSE in EDHOC Appendix C. Use of CBOR, CDDL and COSE in EDHOC
This Appendix is intended to simplify for implementors not familiar This Appendix is intended to simplify for implementors not familiar
with CBOR [RFC8949], CDDL [RFC8610], COSE with CBOR [RFC8949], CDDL [RFC8610], COSE
[I-D.ietf-cose-rfc8152bis-struct], and HKDF [RFC5869]. [I-D.ietf-cose-rfc8152bis-struct], and HKDF [RFC5869].
B.1. CBOR and CDDL C.1. CBOR and CDDL
The Concise Binary Object Representation (CBOR) [RFC8949] is a data The Concise Binary Object Representation (CBOR) [RFC8949] is a data
format designed for small code size and small message size. CBOR format designed for small code size and small message size. CBOR
builds on the JSON data model but extends it by e.g. encoding binary builds on the JSON data model but extends it by e.g. encoding binary
data directly without base64 conversion. In addition to the binary data directly without base64 conversion. In addition to the binary
CBOR encoding, CBOR also has a diagnostic notation that is readable CBOR encoding, CBOR also has a diagnostic notation that is readable
and editable by humans. The Concise Data Definition Language (CDDL) and editable by humans. The Concise Data Definition Language (CDDL)
[RFC8610] provides a way to express structures for protocol messages [RFC8610] provides a way to express structures for protocol messages
and APIs that use CBOR. [RFC8610] also extends the diagnostic and APIs that use CBOR. [RFC8610] also extends the diagnostic
notation. notation.
skipping to change at page 59, line 46 skipping to change at page 61, line 39
h'12cd' 0x4212cd byte string h'12cd' 0x4212cd byte string
'12cd' 0x4431326364 byte string '12cd' 0x4431326364 byte string
"12cd" 0x6431326364 text string "12cd" 0x6431326364 text string
{ 4 : h'cd' } 0xa10441cd map { 4 : h'cd' } 0xa10441cd map
<< 1, 2, null >> 0x430102f6 byte string << 1, 2, null >> 0x430102f6 byte string
[ 1, 2, null ] 0x830102f6 array [ 1, 2, null ] 0x830102f6 array
( 1, 2, null ) 0x0102f6 sequence ( 1, 2, null ) 0x0102f6 sequence
1, 2, null 0x0102f6 sequence 1, 2, null 0x0102f6 sequence
------------------------------------------------------------------ ------------------------------------------------------------------
B.2. CDDL Definitions C.2. CDDL Definitions
This sections compiles the CDDL definitions for ease of reference. This sections compiles the CDDL definitions for ease of reference.
bstr_identifier = bstr / int
suite = int suite = int
SUITES_R : [ supported : 2* suite ] / suite SUITES_R : [ supported : 2* suite ] / suite
message_1 = ( message_1 = (
? C_1 : null, METHOD : int,
METHOD_CORR : int,
SUITES_I : [ selected : suite, supported : 2* suite ] / suite, SUITES_I : [ selected : suite, supported : 2* suite ] / suite,
G_X : bstr, G_X : bstr,
C_I : bstr_identifier, C_I : bstr / int,
? EAD ; EAD_1 ? EAD ; EAD_1
) )
message_2 = ( message_2 = (
data_2, data_2,
CIPHERTEXT_2 : bstr, CIPHERTEXT_2 : bstr,
) )
data_2 = ( data_2 = (
? C_I : bstr_identifier,
G_Y : bstr, G_Y : bstr,
C_R : bstr_identifier, C_R : bstr / int,
) )
message_3 = ( message_3 = (
data_3,
CIPHERTEXT_3 : bstr, CIPHERTEXT_3 : bstr,
) )
data_3 = (
? C_R : bstr_identifier,
)
message_4 = ( message_4 = (
data_4,
CIPHERTEXT_4 : bstr, CIPHERTEXT_4 : bstr,
) )
data_4 = (
? C_I : bstr_identifier,
)
error = ( error = (
? C_x : bstr_identifier,
ERR_CODE : int, ERR_CODE : int,
ERR_INFO : any ERR_INFO : any
) )
info = [ info = [
edhoc_aead_id : int / tstr, edhoc_aead_id : int / tstr,
transcript_hash : bstr, transcript_hash : bstr,
label : tstr, label : tstr,
length : uint length : uint
] ]
B.3. COSE C.3. COSE
CBOR Object Signing and Encryption (COSE) CBOR Object Signing and Encryption (COSE)
[I-D.ietf-cose-rfc8152bis-struct] describes how to create and process [I-D.ietf-cose-rfc8152bis-struct] describes how to create and process
signatures, message authentication codes, and encryption using CBOR. signatures, message authentication codes, and encryption using CBOR.
COSE builds on JOSE, but is adapted to allow more efficient COSE builds on JOSE, but is adapted to allow more efficient
processing in constrained devices. EDHOC makes use of COSE_Key, processing in constrained devices. EDHOC makes use of COSE_Key,
COSE_Encrypt0, and COSE_Sign1 objects. COSE_Encrypt0, and COSE_Sign1 objects.
Appendix C. Test Vectors Appendix D. Test Vectors
Note: The test vectors are not updated to version -07 of the draft. NOTE 0. These test vectors are compatible with versions -05 and -06
More changes affecting the test vectors are anticipated for -08. of the specification.
This appendix provides detailed test vectors to ease implementation This appendix provides detailed test vectors to ease implementation
and ensure interoperability. The test vectors in this version are and ensure interoperability. In addition to hexadecimal, all CBOR
compatible with versions -05 and -06 of the specification. In data items and sequences are given in CBOR diagnostic notation. The
addition to hexadecimal, all CBOR data items and sequences are given test vectors use the default mapping to CoAP where the Initiator acts
in CBOR diagnostic notation. The test vectors use the default as CoAP client (this means that corr = 1).
mapping to CoAP where the Initiator acts as CoAP client (this means
that corr = 1).
A more extensive test vector suite covering more combinations of A more extensive test vector suite covering more combinations of
authentication method used between Initiator and Responder and authentication method used between Initiator and Responder and
related code to generate them can be found at https://github.com/ related code to generate them can be found at https://github.com/
lake-wg/edhoc/tree/master/test-vectors-05. lake-wg/edhoc/tree/master/test-vectors-05.
NOTE 1. In the previous and current test vectors the same name is NOTE 1. In the previous and current test vectors the same name is
used for certain byte strings and their CBOR bstr encodings. For used for certain byte strings and their CBOR bstr encodings. For
example the transcript hash TH_2 is used to denote both the output of example the transcript hash TH_2 is used to denote both the output of
the hash function and the input into the key derivation function, the hash function and the input into the key derivation function,
whereas the latter is a CBOR bstr encoding of the former. Some whereas the latter is a CBOR bstr encoding of the former. Some
attempts are made to clarify that in this Appendix (e.g. using "CBOR attempts are made to clarify that in this Appendix (e.g. using "CBOR
encoded"/"CBOR unencoded"). encoded"/"CBOR unencoded").
NOTE 2. If not clear from the context, remember that CBOR sequences NOTE 2. If not clear from the context, remember that CBOR sequences
and CBOR arrays assume CBOR encoded data items as elements. and CBOR arrays assume CBOR encoded data items as elements.
C.1. Test Vectors for EDHOC Authenticated with Signature Keys (x5t) D.1. Test Vectors for EDHOC Authenticated with Signature Keys (x5t)
EDHOC with signature authentication and X.509 certificates is used. EDHOC with signature authentication and X.509 certificates is used.
In this test vector, the hash value 'x5t' is used to identify the In this test vector, the hash value 'x5t' is used to identify the
certificate. The optional C_1 in message_1 is omitted. No external certificate. The optional C_1 in message_1 is omitted. No external
authorization data is sent in the message exchange. authorization data is sent in the message exchange.
method (Signature Authentication) method (Signature Authentication)
0 0
CoAP is used as transport and the Initiator acts as CoAP client: CoAP is used as transport and the Initiator acts as CoAP client:
skipping to change at page 62, line 37 skipping to change at page 64, line 20
Supported Cipher Suites (1 byte) Supported Cipher Suites (1 byte)
00 00
The Initiator selected the indicated cipher suite. The Initiator selected the indicated cipher suite.
Selected Cipher Suite (int) Selected Cipher Suite (int)
0 0
Cipher suite 0 is supported by both the Initiator and the Responder, Cipher suite 0 is supported by both the Initiator and the Responder,
see Section 3.4. see Section 3.6.
C.1.1. Message_1 D.1.1. Message_1
The Initiator generates its ephemeral key pair. The Initiator generates its ephemeral key pair.
X (Initiator's ephemeral private key) (32 bytes) X (Initiator's ephemeral private key) (32 bytes)
8f 78 1a 09 53 72 f8 5b 6d 9f 61 09 ae 42 26 11 73 4d 7d bf a0 06 9a 2d 8f 78 1a 09 53 72 f8 5b 6d 9f 61 09 ae 42 26 11 73 4d 7d bf a0 06 9a 2d
f2 93 5b b2 e0 53 bf 35 f2 93 5b b2 e0 53 bf 35
G_X (Initiator's ephemeral public key, CBOR unencoded) (32 bytes) G_X (Initiator's ephemeral public key, CBOR unencoded) (32 bytes)
89 8f f7 9a 02 06 7a 16 ea 1e cc b9 0f a5 22 46 f5 aa 4d d6 ec 07 6b ba 89 8f f7 9a 02 06 7a 16 ea 1e cc b9 0f a5 22 46 f5 aa 4d d6 ec 07 6b ba
02 59 d9 04 b7 ec 8b 0c 02 59 d9 04 b7 ec 8b 0c
The Initiator chooses a connection identifier C_I: The Initiator chooses a connection identifier C_I:
Connection identifier chosen by Initiator (1 byte) Connection identifier chosen by Initiator (1 byte)
09 09
Note that since C_I is a byte string in the interval h'00' to h'2f', Note that since C_I is a byte string in the interval h'00' to h'2f',
it is encoded as the corresponding integer subtracted by 24 (see it is encoded as the corresponding integer subtracted by 24. Thus
bstr_identifier in Section 5.1). Thus 0x09 = 09, 9 - 24 = -15, and 0x09 = 09, 9 - 24 = -15, and -15 in CBOR encoding is equal to 0x2e.
-15 in CBOR encoding is equal to 0x2e.
C_I (1 byte) C_I (1 byte)
2e 2e
Since no external authorization data is sent: Since no external authorization data is sent:
EAD_1 (0 bytes) EAD_1 (0 bytes)
The list of supported cipher suites needs to contain the selected The list of supported cipher suites needs to contain the selected
cipher suite. The initiator truncates the list of supported cipher cipher suite. The initiator truncates the list of supported cipher
skipping to change at page 63, line 48 skipping to change at page 65, line 30
h'898FF79A02067A16EA1ECCB90FA52246F5AA4DD6EC076BBA0259D904B7EC8B0C', h'898FF79A02067A16EA1ECCB90FA52246F5AA4DD6EC076BBA0259D904B7EC8B0C',
-15 -15
) )
Which as a CBOR encoded data item is: Which as a CBOR encoded data item is:
message_1 (CBOR Sequence) (37 bytes) message_1 (CBOR Sequence) (37 bytes)
01 00 58 20 89 8f f7 9a 02 06 7a 16 ea 1e cc b9 0f a5 22 46 f5 aa 4d d6 01 00 58 20 89 8f f7 9a 02 06 7a 16 ea 1e cc b9 0f a5 22 46 f5 aa 4d d6
ec 07 6b ba 02 59 d9 04 b7 ec 8b 0c 2e ec 07 6b ba 02 59 d9 04 b7 ec 8b 0c 2e
C.1.2. Message_2 D.1.2. Message_2
Since METHOD_CORR mod 4 equals 1, C_I is omitted from data_2. Since METHOD_CORR mod 4 equals 1, C_I is omitted from data_2.
The Responder generates the following ephemeral key pair. The Responder generates the following ephemeral key pair.
Y (Responder's ephemeral private key) (32 bytes) Y (Responder's ephemeral private key) (32 bytes)
fd 8c d8 77 c9 ea 38 6e 6a f3 4f f7 e6 06 c4 b6 4c a8 31 c8 ba 33 13 4f fd 8c d8 77 c9 ea 38 6e 6a f3 4f f7 e6 06 c4 b6 4c a8 31 c8 ba 33 13 4f
d4 cd 71 67 ca ba ec da d4 cd 71 67 ca ba ec da
G_Y (Responder's ephemeral public key, CBOR unencoded) (32 bytes) G_Y (Responder's ephemeral public key, CBOR unencoded) (32 bytes)
skipping to change at page 65, line 4 skipping to change at page 66, line 35
PK_R (Responder's public authentication key) (32 bytes) PK_R (Responder's public authentication key) (32 bytes)
db d9 dc 8c d0 3f b7 c3 91 35 11 46 2b b2 38 16 47 7c 6b d8 d6 6e f5 a1 db d9 dc 8c d0 3f b7 c3 91 35 11 46 2b b2 38 16 47 7c 6b d8 d6 6e f5 a1
a0 70 ac 85 4e d7 3f d2 a0 70 ac 85 4e d7 3f d2
Since neither the Initiator nor the Responder authenticates with a Since neither the Initiator nor the Responder authenticates with a
static Diffie-Hellman key, PRK_3e2m = PRK_2e static Diffie-Hellman key, PRK_3e2m = PRK_2e
PRK_3e2m (32 bytes) PRK_3e2m (32 bytes)
ec 62 92 a0 67 f1 37 fc 7f 59 62 9d 22 6f bf c4 e0 68 89 49 f6 62 a9 7f ec 62 92 a0 67 f1 37 fc 7f 59 62 9d 22 6f bf c4 e0 68 89 49 f6 62 a9 7f
d8 2f be b7 99 71 39 4a d8 2f be b7 99 71 39 4a
The Responder chooses a connection identifier C_R. The Responder chooses a connection identifier C_R.
Connection identifier chosen by Responder (1 byte) Connection identifier chosen by Responder (1 byte)
00 00
Note that since C_R is a byte string in the interval h'00' to h'2f', Note that since C_R is a byte string in the interval h'00' to h'2f',
it is encoded as the corresponding integer subtracted by 24 (see it is encoded as the corresponding integer subtracted by 24. Thus
bstr_identifier in Section 5.1). Thus 0x00 = 0, 0 - 24 = -24, and 0x00 = 0, 0 - 24 = -24, and -24 in CBOR encoding is equal to 0x37.
-24 in CBOR encoding is equal to 0x37.
C_R (1 byte) C_R (1 byte)
37 37
Data_2 is constructed as the CBOR Sequence of G_Y and C_R, encoded as Data_2 is constructed as the CBOR Sequence of G_Y and C_R, encoded as
CBOR byte strings. The CBOR diagnostic notation is: CBOR byte strings. The CBOR diagnostic notation is:
data_2 = data_2 =
( (
h'71a3d599c21da18902a1aea810b2b6382ccd8d5f9bf0195281754c5ebcaf301e', h'71a3d599c21da18902a1aea810b2b6382ccd8d5f9bf0195281754c5ebcaf301e',
skipping to change at page 68, line 35 skipping to change at page 70, line 18
From these parameters, IV_2m is computed. IV_2m is the output of From these parameters, IV_2m is computed. IV_2m is the output of
HKDF-Expand(PRK_3e2m, info, L), where L is the length of IV_2m, so 13 HKDF-Expand(PRK_3e2m, info, L), where L is the length of IV_2m, so 13
bytes. bytes.
IV_2m (13 bytes) IV_2m (13 bytes)
c8 1e 1a 95 cc 93 b3 36 69 6e d5 02 55 c8 1e 1a 95 cc 93 b3 36 69 6e d5 02 55
Finally, COSE_Encrypt0 is computed from the parameters above. Finally, COSE_Encrypt0 is computed from the parameters above.
* protected header = CBOR-encoded ID_CRED_R o protected header = CBOR-encoded ID_CRED_R
* external_aad = A_2m o external_aad = A_2m
* empty plaintext = P_2m o empty plaintext = P_2m
MAC_2 (CBOR unencoded) (8 bytes) MAC_2 (CBOR unencoded) (8 bytes)
fa bb a4 7e 56 71 a1 82 fa bb a4 7e 56 71 a1 82
To compute the Signature_or_MAC_2, the key is the private To compute the Signature_or_MAC_2, the key is the private
authentication key of the Responder and the message M_2 to be signed authentication key of the Responder and the message M_2 to be signed
= [ "Signature1", << ID_CRED_R >>, << TH_2, CRED_R, ? EAD_2 >>, MAC_2 = [ "Signature1", << ID_CRED_R >>, << TH_2, CRED_R, ? EAD_2 >>, MAC_2
]. ID_CRED_R is encoded as a CBOR byte string, the concatenation of ]. ID_CRED_R is encoded as a CBOR byte string, the concatenation of
the CBOR byte strings TH_2 and CRED_R is wrapped as a CBOR bstr, and the CBOR byte strings TH_2 and CRED_R is wrapped as a CBOR bstr, and
MAC_2 is encoded as a CBOR bstr. MAC_2 is encoded as a CBOR bstr.
skipping to change at page 69, line 41 skipping to change at page 71, line 28
Signature_or_MAC_2 (CBOR unencoded) (64 bytes) Signature_or_MAC_2 (CBOR unencoded) (64 bytes)
1f 17 00 6a 98 48 c9 77 cb bd ca a7 57 b6 fd 46 82 c8 17 39 e1 5c 99 37 1f 17 00 6a 98 48 c9 77 cb bd ca a7 57 b6 fd 46 82 c8 17 39 e1 5c 99 37
c2 1c f5 e9 a0 e6 03 9f 54 fd 2a 6c 3a 11 18 f2 b9 d8 eb cd 48 23 48 b9 c2 1c f5 e9 a0 e6 03 9f 54 fd 2a 6c 3a 11 18 f2 b9 d8 eb cd 48 23 48 b9
9c 3e d7 ed 1b d9 80 6c 93 c8 90 68 e8 36 b4 0f 9c 3e d7 ed 1b d9 80 6c 93 c8 90 68 e8 36 b4 0f
CIPHERTEXT_2 is the ciphertext resulting from XOR between plaintext CIPHERTEXT_2 is the ciphertext resulting from XOR between plaintext
and KEYSTREAM_2 which is derived from TH_2 and the pseudorandom key and KEYSTREAM_2 which is derived from TH_2 and the pseudorandom key
PRK_2e. PRK_2e.
* plaintext = CBOR Sequence of the items ID_CRED_R and o plaintext = CBOR Sequence of the items ID_CRED_R and
Signature_or_MAC_2 encoded as CBOR byte strings, in this order Signature_or_MAC_2 encoded as CBOR byte strings, in this order
(EAD_2 is empty). (EAD_2 is empty).
The plaintext is the following: The plaintext is the following:
P_2e (CBOR Sequence) (80 bytes) P_2e (CBOR Sequence) (80 bytes)
a1 18 22 82 2e 48 68 44 07 8a 53 f3 12 f5 58 40 1f 17 00 6a 98 48 c9 77 a1 18 22 82 2e 48 68 44 07 8a 53 f3 12 f5 58 40 1f 17 00 6a 98 48 c9 77
cb bd ca a7 57 b6 fd 46 82 c8 17 39 e1 5c 99 37 c2 1c f5 e9 a0 e6 03 9f cb bd ca a7 57 b6 fd 46 82 c8 17 39 e1 5c 99 37 c2 1c f5 e9 a0 e6 03 9f
54 fd 2a 6c 3a 11 18 f2 b9 d8 eb cd 48 23 48 b9 9c 3e d7 ed 1b d9 80 6c 54 fd 2a 6c 3a 11 18 f2 b9 d8 eb cd 48 23 48 b9 9c 3e d7 ed 1b d9 80 6c
93 c8 90 68 e8 36 b4 0f 93 c8 90 68 e8 36 b4 0f
skipping to change at page 71, line 12 skipping to change at page 72, line 47
Which as a CBOR encoded data item is: Which as a CBOR encoded data item is:
message_2 (CBOR Sequence) (117 bytes) message_2 (CBOR Sequence) (117 bytes)
58 20 71 a3 d5 99 c2 1d a1 89 02 a1 ae a8 10 b2 b6 38 2c cd 8d 5f 9b f0 58 20 71 a3 d5 99 c2 1d a1 89 02 a1 ae a8 10 b2 b6 38 2c cd 8d 5f 9b f0
19 52 81 75 4c 5e bc af 30 1e 37 58 50 0f f2 ac 2d 7e 87 ae 34 0e 50 bb 19 52 81 75 4c 5e bc af 30 1e 37 58 50 0f f2 ac 2d 7e 87 ae 34 0e 50 bb
de 9f 70 e8 a7 7f 86 bf 65 9f 43 b0 24 a7 3e e9 7b 6a 2b 9c 55 92 fd 83 de 9f 70 e8 a7 7f 86 bf 65 9f 43 b0 24 a7 3e e9 7b 6a 2b 9c 55 92 fd 83
5a 15 17 8b 7c 28 af 54 74 a9 75 81 48 64 7d 3d 98 a8 73 1e 16 4c 9c 70 5a 15 17 8b 7c 28 af 54 74 a9 75 81 48 64 7d 3d 98 a8 73 1e 16 4c 9c 70
52 81 07 f4 0f 21 46 3b a8 11 bf 03 97 19 e7 cf fa a7 f2 f4 40 52 81 07 f4 0f 21 46 3b a8 11 bf 03 97 19 e7 cf fa a7 f2 f4 40
C.1.3. Message_3 D.1.3. Message_3
Since corr equals 1, C_R is not omitted from data_3. Since corr equals 1, C_R is not omitted from data_3.
The Initiator's sign/verify key pair is the following: The Initiator's sign/verify key pair is the following:
SK_I (Initiator's private authentication key) (32 bytes) SK_I (Initiator's private authentication key) (32 bytes)
2f fc e7 a0 b2 b8 25 d3 97 d0 cb 54 f7 46 e3 da 3f 27 59 6e e0 6b 53 71 2f fc e7 a0 b2 b8 25 d3 97 d0 cb 54 f7 46 e3 da 3f 27 59 6e e0 6b 53 71
48 1d c0 e0 12 bc 34 d7 48 1d c0 e0 12 bc 34 d7
PK_I (Responder's public authentication key) (32 bytes) PK_I (Responder's public authentication key) (32 bytes)
skipping to change at page 74, line 32 skipping to change at page 76, line 22
9c 83 9c 0e e8 36 42 50 5a 8e 1c 9f b2 9c 83 9c 0e e8 36 42 50 5a 8e 1c 9f b2
MAC_3 is the 'ciphertext' of the COSE_Encrypt0: MAC_3 is the 'ciphertext' of the COSE_Encrypt0:
MAC_3 (CBOR unencoded) (8 bytes) MAC_3 (CBOR unencoded) (8 bytes)
2f a1 e3 9e ae 7d 5f 8d 2f a1 e3 9e ae 7d 5f 8d
Since the method = 0, Signature_or_MAC_3 is a signature. The Since the method = 0, Signature_or_MAC_3 is a signature. The
algorithm with selected cipher suite 0 is Ed25519. algorithm with selected cipher suite 0 is Ed25519.
* The message M_3 to be signed = [ "Signature1", << ID_CRED_I >>, o The message M_3 to be signed = [ "Signature1", << ID_CRED_I >>,
<< TH_3, CRED_I >>, MAC_3 ], i.e. ID_CRED_I encoded as CBOR bstr, << TH_3, CRED_I >>, MAC_3 ], i.e. ID_CRED_I encoded as CBOR bstr,
the concatenation of the CBOR byte strings TH_3 and CRED_I wrapped the concatenation of the CBOR byte strings TH_3 and CRED_I wrapped
as a CBOR bstr, and MAC_3 encoded as a CBOR bstr. as a CBOR bstr, and MAC_3 encoded as a CBOR bstr.
* The signing key is the private authentication key of the o The signing key is the private authentication key of the
Initiator. Initiator.
M_3 = M_3 =
[ [
"Signature1", "Signature1",
h'A11822822E48705D5845F36FC6A6', h'A11822822E48705D5845F36FC6A6',
h'5820F24D18CAFCE374D4E3736329C152AB3AEA9C7C0F650C3070B6F51E68E2AEBB6 h'5820F24D18CAFCE374D4E3736329C152AB3AEA9C7C0F650C3070B6F51E68E2AEBB6
058655413204C3EBC3428A6CF57E24C9DEF59651770449BCE7EC6561E52433AA55E71 058655413204C3EBC3428A6CF57E24C9DEF59651770449BCE7EC6561E52433AA55E71
F1FA34B22A9CA4A1E12924EAE1D1766088098449CB848FFC795F88AFC49CBE8AFDD1B F1FA34B22A9CA4A1E12924EAE1D1766088098449CB848FFC795F88AFC49CBE8AFDD1B
A009F21675E8F6C77A4A2C30195601F6F0A0852978BD43D28207D44486502FF7BDD A009F21675E8F6C77A4A2C30195601F6F0A0852978BD43D28207D44486502FF7BDD
skipping to change at page 77, line 12 skipping to change at page 79, line 4
From the parameter above, message_3 is computed, as the CBOR Sequence From the parameter above, message_3 is computed, as the CBOR Sequence
of the following CBOR encoded data items: (C_R, CIPHERTEXT_3). of the following CBOR encoded data items: (C_R, CIPHERTEXT_3).
message_3 = message_3 =
( (
-24, -24,
h'F5F6DEBD8214051CD583C84096C4801DEBF35B15363DD16EBD8530DFDCFB34FCD2EB h'F5F6DEBD8214051CD583C84096C4801DEBF35B15363DD16EBD8530DFDCFB34FCD2EB
6CAD1DAC66A479FB38DEAAF1D30A7E6817A22AB04F3D5B1E972A0D13EA86C66B60514C 6CAD1DAC66A479FB38DEAAF1D30A7E6817A22AB04F3D5B1E972A0D13EA86C66B60514C
9657EA89C57B0401EDC5AA8BBCAB813CC5D6E7' 9657EA89C57B0401EDC5AA8BBCAB813CC5D6E7'
) )
Which encodes to the following byte string: Which encodes to the following byte string:
message_3 (CBOR Sequence) (91 bytes) message_3 (CBOR Sequence) (91 bytes)
37 58 58 f5 f6 de bd 82 14 05 1c d5 83 c8 40 96 c4 80 1d eb f3 5b 15 36 37 58 58 f5 f6 de bd 82 14 05 1c d5 83 c8 40 96 c4 80 1d eb f3 5b 15 36
3d d1 6e bd 85 30 df dc fb 34 fc d2 eb 6c ad 1d ac 66 a4 79 fb 38 de aa 3d d1 6e bd 85 30 df dc fb 34 fc d2 eb 6c ad 1d ac 66 a4 79 fb 38 de aa
f1 d3 0a 7e 68 17 a2 2a b0 4f 3d 5b 1e 97 2a 0d 13 ea 86 c6 6b 60 51 4c f1 d3 0a 7e 68 17 a2 2a b0 4f 3d 5b 1e 97 2a 0d 13 ea 86 c6 6b 60 51 4c
96 57 ea 89 c5 7b 04 01 ed c5 aa 8b bc ab 81 3c c5 d6 e7 96 57 ea 89 c5 7b 04 01 ed c5 aa 8b bc ab 81 3c c5 d6 e7
C.1.4. OSCORE Security Context Derivation D.1.4. OSCORE Security Context Derivation
From here, the Initiator and the Responder can derive an OSCORE From here, the Initiator and the Responder can derive an OSCORE
Security Context, using the EDHOC-Exporter interface. Security Context, using the EDHOC-Exporter interface.
From TH_3 and CIPHERTEXT_3, compute the input to the transcript hash From TH_3 and CIPHERTEXT_3, compute the input to the transcript hash
TH_4 = H( TH_3, CIPHERTEXT_3 ), as a CBOR Sequence of these 2 data TH_4 = H( TH_3, CIPHERTEXT_3 ), as a CBOR Sequence of these 2 data
items. items.
Input to calculate TH_4 (CBOR Sequence) (124 bytes) Input to calculate TH_4 (CBOR Sequence) (124 bytes)
58 20 f2 4d 18 ca fc e3 74 d4 e3 73 63 29 c1 52 ab 3a ea 9c 7c 0f 65 0c 58 20 f2 4d 18 ca fc e3 74 d4 e3 73 63 29 c1 52 ab 3a ea 9c 7c 0f 65 0c
skipping to change at page 79, line 10 skipping to change at page 81, line 4
5e c3 ee 41 7c fb ba e9 5e c3 ee 41 7c fb ba e9
The client's OSCORE Sender ID is C_R and the server's OSCORE Sender The client's OSCORE Sender ID is C_R and the server's OSCORE Sender
ID is C_I. ID is C_I.
Client's OSCORE Sender ID (1 byte) Client's OSCORE Sender ID (1 byte)
00 00
Server's OSCORE Sender ID (1 byte) Server's OSCORE Sender ID (1 byte)
09 09
The AEAD Algorithm and the hash algorithm are the application AEAD The AEAD Algorithm and the hash algorithm are the application AEAD
and hash algorithms in the selected cipher suite. and hash algorithms in the selected cipher suite.
OSCORE AEAD Algorithm (int) OSCORE AEAD Algorithm (int)
10 10
OSCORE Hash Algorithm (int) OSCORE Hash Algorithm (int)
-16 -16
C.2. Test Vectors for EDHOC Authenticated with Static Diffie-Hellman D.2. Test Vectors for EDHOC Authenticated with Static Diffie-Hellman
Keys Keys
EDHOC with static Diffie-Hellman keys and raw public keys is used. EDHOC with static Diffie-Hellman keys and raw public keys is used.
In this test vector, a key identifier is used to identify the raw In this test vector, a key identifier is used to identify the raw
public key. The optional C_1 in message_1 is omitted. No external public key. The optional C_1 in message_1 is omitted. No external
authorization data is sent in the message exchange. authorization data is sent in the message exchange.
method (Static DH Based Authentication) method (Static DH Based Authentication)
3 3
skipping to change at page 80, line 4 skipping to change at page 81, line 44
The Initiator indicates only one cipher suite in the (potentially The Initiator indicates only one cipher suite in the (potentially
truncated) list of cipher suites. truncated) list of cipher suites.
Supported Cipher Suites (1 byte) Supported Cipher Suites (1 byte)
00 00
The Initiator selected the indicated cipher suite. The Initiator selected the indicated cipher suite.
Selected Cipher Suite (int) Selected Cipher Suite (int)
0 0
Cipher suite 0 is supported by both the Initiator and the Responder, Cipher suite 0 is supported by both the Initiator and the Responder,
see Section 3.4. see Section 3.6.
C.2.1. Message_1 D.2.1. Message_1
The Initiator generates its ephemeral key pair. The Initiator generates its ephemeral key pair.
X (Initiator's ephemeral private key) (32 bytes) X (Initiator's ephemeral private key) (32 bytes)
ae 11 a0 db 86 3c 02 27 e5 39 92 fe b8 f5 92 4c 50 d0 a7 ba 6e ea b4 ad ae 11 a0 db 86 3c 02 27 e5 39 92 fe b8 f5 92 4c 50 d0 a7 ba 6e ea b4 ad
1f f2 45 72 f4 f5 7c fa 1f f2 45 72 f4 f5 7c fa
G_X (Initiator's ephemeral public key, CBOR unencoded) (32 bytes) G_X (Initiator's ephemeral public key, CBOR unencoded) (32 bytes)
8d 3e f5 6d 1b 75 0a 43 51 d6 8a c2 50 a0 e8 83 79 0e fc 80 a5 38 a4 44 8d 3e f5 6d 1b 75 0a 43 51 d6 8a c2 50 a0 e8 83 79 0e fc 80 a5 38 a4 44
ee 9e 2b 57 e2 44 1a 7c ee 9e 2b 57 e2 44 1a 7c
The Initiator chooses a connection identifier C_I: The Initiator chooses a connection identifier C_I:
Connection identifier chosen by Initiator (1 byte) Connection identifier chosen by Initiator (1 byte)
16 16
Note that since C_I is a byte string in the interval h'00' to h'2f', Note that since C_I is a byte string in the interval h'00' to h'2f',
it is encoded as the corresponding integer - 24 (see bstr_identifier it is encoded as the corresponding integer - 24, i.e. 0x16 = 22, 22 -
in Section 5.1), i.e. 0x16 = 22, 22 - 24 = -2, and -2 in CBOR 24 = -2, and -2 in CBOR encoding is equal to 0x21.
encoding is equal to 0x21.
C_I (1 byte) C_I (1 byte)
21 21
Since no external authorization data is sent: Since no external authorization data is sent:
EAD_1 (0 bytes) EAD_1 (0 bytes)
Since the list of supported cipher suites needs to contain the Since the list of supported cipher suites needs to contain the
selected cipher suite, the initiator truncates the list of supported selected cipher suite, the initiator truncates the list of supported
skipping to change at page 81, line 12 skipping to change at page 83, line 4
message_1 is constructed as the CBOR Sequence of the data items above message_1 is constructed as the CBOR Sequence of the data items above
encoded as CBOR. In CBOR diagnostic notation: encoded as CBOR. In CBOR diagnostic notation:
message_1 = message_1 =
( (
13, 13,
0, 0,
h'8D3EF56D1B750A4351D68AC250A0E883790EFC80A538A444EE9E2B57E2441A7C', h'8D3EF56D1B750A4351D68AC250A0E883790EFC80A538A444EE9E2B57E2441A7C',
-2 -2
) )
Which as a CBOR encoded data item is: Which as a CBOR encoded data item is:
message_1 (CBOR Sequence) (37 bytes) message_1 (CBOR Sequence) (37 bytes)
0d 00 58 20 8d 3e f5 6d 1b 75 0a 43 51 d6 8a c2 50 a0 e8 83 79 0e fc 80 0d 00 58 20 8d 3e f5 6d 1b 75 0a 43 51 d6 8a c2 50 a0 e8 83 79 0e fc 80
a5 38 a4 44 ee 9e 2b 57 e2 44 1a 7c 21 a5 38 a4 44 ee 9e 2b 57 e2 44 1a 7c 21
C.2.2. Message_2 D.2.2. Message_2
Since METHOD_CORR mod 4 equals 1, C_I is omitted from data_2. Since METHOD_CORR mod 4 equals 1, C_I is omitted from data_2.
The Responder generates the following ephemeral key pair. The Responder generates the following ephemeral key pair.
Y (Responder's ephemeral private key) (32 bytes) Y (Responder's ephemeral private key) (32 bytes)
c6 46 cd dc 58 12 6e 18 10 5f 01 ce 35 05 6e 5e bc 35 f4 d4 cc 51 07 49 c6 46 cd dc 58 12 6e 18 10 5f 01 ce 35 05 6e 5e bc 35 f4 d4 cc 51 07 49
a3 a5 e0 69 c1 16 16 9a a3 a5 e0 69 c1 16 16 9a
G_Y (Responder's ephemeral public key, CBOR unencoded) (32 bytes) G_Y (Responder's ephemeral public key, CBOR unencoded) (32 bytes)
skipping to change at page 82, line 14 skipping to change at page 84, line 4
PRK_2e (32 bytes) PRK_2e (32 bytes)
93 9f cb 05 6d 2e 41 4f 1b ec 61 04 61 99 c2 c7 63 d2 7f 0c 3d 15 fa 16 93 9f cb 05 6d 2e 41 4f 1b ec 61 04 61 99 c2 c7 63 d2 7f 0c 3d 15 fa 16
71 fa 13 4e 0d c5 a0 4d 71 fa 13 4e 0d c5 a0 4d
The Responder's static Diffie-Hellman key pair is the following: The Responder's static Diffie-Hellman key pair is the following:
R (Responder's private authentication key) (32 bytes) R (Responder's private authentication key) (32 bytes)
bb 50 1a ac 67 b9 a9 5f 97 e0 ed ed 6b 82 a6 62 93 4f bb fc 7a d1 b7 4c bb 50 1a ac 67 b9 a9 5f 97 e0 ed ed 6b 82 a6 62 93 4f bb fc 7a d1 b7 4c
1f ca d6 6a 07 94 22 d0 1f ca d6 6a 07 94 22 d0
G_R (Responder's public authentication key) (32 bytes) G_R (Responder's public authentication key) (32 bytes)
a3 ff 26 35 95 be b3 77 d1 a0 ce 1d 04 da d2 d4 09 66 ac 6b cb 62 20 51 a3 ff 26 35 95 be b3 77 d1 a0 ce 1d 04 da d2 d4 09 66 ac 6b cb 62 20 51
b8 46 59 18 4d 5d 9a 32 b8 46 59 18 4d 5d 9a 32
Since the Responder authenticates with a static Diffie-Hellman key, Since the Responder authenticates with a static Diffie-Hellman key,
PRK_3e2m = HKDF-Extract( PRK_2e, G_RX ), where G_RX is the ECDH PRK_3e2m = HKDF-Extract( PRK_2e, G_RX ), where G_RX is the ECDH
shared secret calculated from G_R and X, or G_X and R. shared secret calculated from G_R and X, or G_X and R.
From the Responder's authentication key and the Initiator's ephemeral From the Responder's authentication key and the Initiator's ephemeral
key (see Appendix C.2.1), the ECDH shared secret G_RX is calculated. key (see Appendix D.2.1), the ECDH shared secret G_RX is calculated.
G_RX (ECDH shared secret) (32 bytes) G_RX (ECDH shared secret) (32 bytes)
21 c7 ef f4 fb 69 fa 4b 67 97 d0 58 84 31 5d 84 11 a3 fd a5 4f 6d ad a6 21 c7 ef f4 fb 69 fa 4b 67 97 d0 58 84 31 5d 84 11 a3 fd a5 4f 6d ad a6
1d 4f cd 85 e7 90 66 68 1d 4f cd 85 e7 90 66 68
PRK_3e2m (32 bytes) PRK_3e2m (32 bytes)
75 07 7c 69 1e 35 01 2d 48 bc 24 c8 4f 2b ab 89 f5 2f ac 03 fe dd 81 3e 75 07 7c 69 1e 35 01 2d 48 bc 24 c8 4f 2b ab 89 f5 2f ac 03 fe dd 81 3e
43 8c 93 b1 0b 39 93 07 43 8c 93 b1 0b 39 93 07
The Responder chooses a connection identifier C_R. The Responder chooses a connection identifier C_R.
Connection identifier chosen by Responder (1 byte) Connection identifier chosen by Responder (1 byte)
00 00
Note that since C_R is a byte string in the interval h'00' to h'2f', Note that since C_R is a byte string in the interval h'00' to h'2f',
it is encoded as the corresponding integer - 24 (see bstr_identifier it is encoded as the corresponding integer - 24, i.e. 0x00 = 0, 0 -
in Section 5.1), i.e. 0x00 = 0, 0 - 24 = -24, and -24 in CBOR 24 = -24, and -24 in CBOR encoding is equal to 0x37.
encoding is equal to 0x37.
C_R (1 byte) C_R (1 byte)
37 37
Data_2 is constructed as the CBOR Sequence of G_Y and C_R. Data_2 is constructed as the CBOR Sequence of G_Y and C_R.
data_2 = data_2 =
( (
h'52FBA0BDC8D953DD86CE1AB2FD7C05A4658C7C30AFDBFC3301047069451BAF35', h'52FBA0BDC8D953DD86CE1AB2FD7C05A4658C7C30AFDBFC3301047069451BAF35',
-24 -24
skipping to change at page 84, line 7 skipping to change at page 85, line 36
4: h'05' 4: h'05'
} }
ID_CRED_R (4 bytes) ID_CRED_R (4 bytes)
a1 04 41 05 a1 04 41 05
CRED_R is the following COSE_Key: CRED_R is the following COSE_Key:
{ {
1: 1, 1: 1,
-1: 4, -1: 4,
-2: h'A3FF263595BEB377D1A0CE1D04DAD2D40966AC6BCB622051B84659184D5D9A32, -2: h'A3FF263595BEB377D1A0CE1D04DAD2D40966AC6BCB622051B84659184D5D9A32,
"subject name": "" "subject name": ""
} }
Which encodes to the following byte string: Which encodes to the following byte string:
CRED_R (54 bytes) CRED_R (54 bytes)
a4 01 01 20 04 21 58 20 a3 ff 26 35 95 be b3 77 d1 a0 ce 1d 04 da d2 d4 a4 01 01 20 04 21 58 20 a3 ff 26 35 95 be b3 77 d1 a0 ce 1d 04 da d2 d4
09 66 ac 6b cb 62 20 51 b8 46 59 18 4d 5d 9a 32 6c 73 75 62 6a 65 63 74 09 66 ac 6b cb 62 20 51 b8 46 59 18 4d 5d 9a 32 6c 73 75 62 6a 65 63 74
20 6e 61 6d 65 60 20 6e 61 6d 65 60
skipping to change at page 85, line 51 skipping to change at page 87, line 29
From these parameters, IV_2m is computed. IV_2m is the output of From these parameters, IV_2m is computed. IV_2m is the output of
HKDF-Expand(PRK_3e2m, info, L), where L is the length of IV_2m, so 13 HKDF-Expand(PRK_3e2m, info, L), where L is the length of IV_2m, so 13
bytes. bytes.
IV_2m (13 bytes) IV_2m (13 bytes)
e9 b8 e4 b1 bd 02 f4 9a 82 0d d3 53 4f e9 b8 e4 b1 bd 02 f4 9a 82 0d d3 53 4f
Finally, COSE_Encrypt0 is computed from the parameters above. Finally, COSE_Encrypt0 is computed from the parameters above.
* protected header = CBOR-encoded ID_CRED_R o protected header = CBOR-encoded ID_CRED_R
* external_aad = A_2m
* empty plaintext = P_2m o external_aad = A_2m
o empty plaintext = P_2m
MAC_2 is the 'ciphertext' of the COSE_Encrypt0 with empty plaintext. MAC_2 is the 'ciphertext' of the COSE_Encrypt0 with empty plaintext.
In case of cipher suite 0 the AEAD is AES-CCM truncated to 8 bytes: In case of cipher suite 0 the AEAD is AES-CCM truncated to 8 bytes:
MAC_2 (CBOR unencoded) (8 bytes) MAC_2 (CBOR unencoded) (8 bytes)
42 e7 99 78 43 1e 6b 8f 42 e7 99 78 43 1e 6b 8f
Since method = 2, Signature_or_MAC_2 is MAC_2: Since method = 2, Signature_or_MAC_2 is MAC_2:
Signature_or_MAC_2 (CBOR unencoded) (8 bytes) Signature_or_MAC_2 (CBOR unencoded) (8 bytes)
skipping to change at page 86, line 29 skipping to change at page 88, line 8
CIPHERTEXT_2 is the ciphertext resulting from XOR between plaintext CIPHERTEXT_2 is the ciphertext resulting from XOR between plaintext
and KEYSTREAM_2 which is derived from TH_2 and the pseudorandom key and KEYSTREAM_2 which is derived from TH_2 and the pseudorandom key
PRK_2e. PRK_2e.
The plaintext is the CBOR Sequence of the items ID_CRED_R and the The plaintext is the CBOR Sequence of the items ID_CRED_R and the
CBOR encoded Signature_or_MAC_2, in this order (EAD_2 is empty). CBOR encoded Signature_or_MAC_2, in this order (EAD_2 is empty).
Note that since ID_CRED_R contains a single 'kid' parameter, i.e., Note that since ID_CRED_R contains a single 'kid' parameter, i.e.,
ID_CRED_R = { 4 : kid_R }, only the byte string kid_R is conveyed in ID_CRED_R = { 4 : kid_R }, only the byte string kid_R is conveyed in
the plaintext encoded as a bstr_identifier. kid_R is encoded as the the plaintext encoded as a bstr_identifier. kid_R is encoded as the
corresponding integer - 24 (see bstr_identifier in Section 5.1), i.e. corresponding integer - 24, i.e. 0x05 = 5, 5 - 24 = -19, and -19 in
0x05 = 5, 5 - 24 = -19, and -19 in CBOR encoding is equal to 0x32. CBOR encoding is equal to 0x32.
The plaintext is the following: The plaintext is the following:
P_2e (CBOR Sequence) (10 bytes) P_2e (CBOR Sequence) (10 bytes)
32 48 42 e7 99 78 43 1e 6b 8f 32 48 42 e7 99 78 43 1e 6b 8f
KEYSTREAM_2 = HKDF-Expand( PRK_2e, info, length ), where length is KEYSTREAM_2 = HKDF-Expand( PRK_2e, info, length ), where length is
the length of the plaintext, so 10. the length of the plaintext, so 10.
info for KEYSTREAM_2 = info for KEYSTREAM_2 =
skipping to change at page 87, line 29 skipping to change at page 89, line 4
a3 f1 bd 5d 02 8d 19 cf 3c 99 a3 f1 bd 5d 02 8d 19 cf 3c 99
message_2 is the CBOR Sequence of data_2 and CIPHERTEXT_2, in this message_2 is the CBOR Sequence of data_2 and CIPHERTEXT_2, in this
order: order:
message_2 = message_2 =
( (
data_2, data_2,
h'A3F1BD5D028D19CF3C99' h'A3F1BD5D028D19CF3C99'
) )
Which as a CBOR encoded data item is: Which as a CBOR encoded data item is:
message_2 (CBOR Sequence) (46 bytes) message_2 (CBOR Sequence) (46 bytes)
58 20 52 fb a0 bd c8 d9 53 dd 86 ce 1a b2 fd 7c 05 a4 65 8c 7c 30 af db 58 20 52 fb a0 bd c8 d9 53 dd 86 ce 1a b2 fd 7c 05 a4 65 8c 7c 30 af db
fc 33 01 04 70 69 45 1b af 35 37 4a a3 f1 bd 5d 02 8d 19 cf 3c 99 fc 33 01 04 70 69 45 1b af 35 37 4a a3 f1 bd 5d 02 8d 19 cf 3c 99
C.2.3. Message_3 D.2.3. Message_3
Since corr equals 1, C_R is not omitted from data_3. Since corr equals 1, C_R is not omitted from data_3.
The Initiator's static Diffie-Hellman key pair is the following: The Initiator's static Diffie-Hellman key pair is the following:
I (Initiator's private authentication key) (32 bytes) I (Initiator's private authentication key) (32 bytes)
2b be a6 55 c2 33 71 c3 29 cf bd 3b 1f 02 c6 c0 62 03 38 37 b8 b5 90 99 2b be a6 55 c2 33 71 c3 29 cf bd 3b 1f 02 c6 c0 62 03 38 37 b8 b5 90 99
a4 43 6f 66 60 81 b0 8e a4 43 6f 66 60 81 b0 8e
G_I (Initiator's public authentication key, CBOR unencoded) (32 bytes) G_I (Initiator's public authentication key, CBOR unencoded) (32 bytes)
2c 44 0c c1 21 f8 d7 f2 4c 3b 0e 41 ae da fe 9c aa 4f 4e 7a bb 83 5e c3 2c 44 0c c1 21 f8 d7 f2 4c 3b 0e 41 ae da fe 9c aa 4f 4e 7a bb 83 5e c3
0f 1d e8 8a db 96 ff 71 0f 1d e8 8a db 96 ff 71
HKDF SHA-256 is the HKDF used (as defined by cipher suite 0). HKDF SHA-256 is the HKDF used (as defined by cipher suite 0).
From the Initiator's authentication key and the Responder's ephemeral From the Initiator's authentication key and the Responder's ephemeral
key (see Appendix C.2.2), the ECDH shared secret G_IY is calculated. key (see Appendix D.2.2), the ECDH shared secret G_IY is calculated.
G_IY (ECDH shared secret) (32 bytes) G_IY (ECDH shared secret) (32 bytes)
cb ff 8c d3 4a 81 df ec 4c b6 5d 9a 57 2e bd 09 64 45 0c 78 56 3d a4 98 cb ff 8c d3 4a 81 df ec 4c b6 5d 9a 57 2e bd 09 64 45 0c 78 56 3d a4 98
1d 80 d3 6c 8b 1a 75 2a 1d 80 d3 6c 8b 1a 75 2a
PRK_4x3m = HMAC-SHA-256 (PRK_3e2m, G_IY). PRK_4x3m = HMAC-SHA-256 (PRK_3e2m, G_IY).
PRK_4x3m (32 bytes) PRK_4x3m (32 bytes)
02 56 2f 1f 01 78 5c 0a a5 f5 94 64 0c 49 cb f6 9f 72 2e 9e 6c 57 83 7d 02 56 2f 1f 01 78 5c 0a a5 f5 94 64 0c 49 cb f6 9f 72 2e 9e 6c 57 83 7d
8e 15 79 ec 45 fe 64 7a 8e 15 79 ec 45 fe 64 7a
skipping to change at page 89, line 4 skipping to change at page 90, line 25
And its credential is: And its credential is:
ID_CRED_I = ID_CRED_I =
{ {
4: h'23' 4: h'23'
} }
ID_CRED_I (4 bytes) ID_CRED_I (4 bytes)
a1 04 41 23 a1 04 41 23
CRED_I is the following COSE_Key: CRED_I is the following COSE_Key:
{ {
1: 1, 1:1,
-1: 4, -1:4,
-2: h'2C440CC121F8D7F24C3B0E41AEDAFE9CAA4F4E7ABB835EC30F1DE88ADB96FF71', -2:h'2C440CC121F8D7F24C3B0E41AEDAFE9CAA4F4E7ABB835EC30F1DE88ADB96FF71',
"subject name": "" "subject name":""
} }
Which encodes to the following byte string: Which encodes to the following byte string:
CRED_I (54 bytes) CRED_I (54 bytes)
a4 01 01 20 04 21 58 20 2c 44 0c c1 21 f8 d7 f2 4c 3b 0e 41 ae da fe 9c a4 01 01 20 04 21 58 20 2c 44 0c c1 21 f8 d7 f2 4c 3b 0e 41 ae da fe 9c
aa 4f 4e 7a bb 83 5e c3 0f 1d e8 8a db 96 ff 71 6c 73 75 62 6a 65 63 74 aa 4f 4e 7a bb 83 5e c3 0f 1d e8 8a db 96 ff 71 6c 73 75 62 6a 65 63 74
20 6e 61 6d 65 60 20 6e 61 6d 65 60
Since no external authorization data is exchanged: Since no external authorization data is exchanged:
skipping to change at page 91, line 11 skipping to change at page 92, line 28
ee 59 8e a6 61 17 dc c3 ee 59 8e a6 61 17 dc c3
Finally, the outer COSE_Encrypt0 is computed. Finally, the outer COSE_Encrypt0 is computed.
The plaintext is the CBOR Sequence of the items ID_CRED_I and the The plaintext is the CBOR Sequence of the items ID_CRED_I and the
CBOR encoded Signature_or_MAC_3, in this order (EAD_3 is empty). CBOR encoded Signature_or_MAC_3, in this order (EAD_3 is empty).
Note that since ID_CRED_I contains a single 'kid' parameter, i.e., Note that since ID_CRED_I contains a single 'kid' parameter, i.e.,
ID_CRED_I = { 4 : kid_I }, only the byte string kid_I is conveyed in ID_CRED_I = { 4 : kid_I }, only the byte string kid_I is conveyed in
the plaintext encoded as a bstr_identifier. kid_I is encoded as the the plaintext encoded as a bstr_identifier. kid_I is encoded as the
corresponding integer - 24 (see bstr_identifier in Section 5.1), i.e. corresponding integer - 24, i.e. 0x23 = 35, 35 - 24 = 11, and 11 in
0x23 = 35, 35 - 24 = 11, and 11 in CBOR encoding is equal to 0x0b. CBOR encoding is equal to 0x0b.
P_3ae (CBOR Sequence) (10 bytes) P_3ae (CBOR Sequence) (10 bytes)
0b 48 ee 59 8e a6 61 17 dc c3 0b 48 ee 59 8e a6 61 17 dc c3
The Associated data A is the following: Associated data A = [ The Associated data A is the following: Associated data A = [
"Encrypt0", h'', TH_3 ] "Encrypt0", h'', TH_3 ]
A_3ae (CBOR-encoded) (45 bytes) A_3ae (CBOR-encoded) (45 bytes)
83 68 45 6e 63 72 79 70 74 30 40 58 20 b6 cd 80 4f c4 b9 d7 ca c5 02 ab 83 68 45 6e 63 72 79 70 74 30 40 58 20 b6 cd 80 4f c4 b9 d7 ca c5 02 ab
d7 7c da 74 e4 1c b0 11 82 d7 cb 8b 84 db 03 ff a5 83 a3 5f cb d7 7c da 74 e4 1c b0 11 82 d7 cb 8b 84 db 03 ff a5 83 a3 5f cb
skipping to change at page 92, line 46 skipping to change at page 94, line 16
( (
-24, -24,
h'D5535F3147E85F1CFACD9E78ABF9E0A81BBF' h'D5535F3147E85F1CFACD9E78ABF9E0A81BBF'
) )
Which encodes to the following byte string: Which encodes to the following byte string:
message_3 (CBOR Sequence) (20 bytes) message_3 (CBOR Sequence) (20 bytes)
37 52 d5 53 5f 31 47 e8 5f 1c fa cd 9e 78 ab f9 e0 a8 1b bf 37 52 d5 53 5f 31 47 e8 5f 1c fa cd 9e 78 ab f9 e0 a8 1b bf
C.2.4. OSCORE Security Context Derivation D.2.4. OSCORE Security Context Derivation
From here, the Initiator and the Responder can derive an OSCORE From here, the Initiator and the Responder can derive an OSCORE
Security Context, using the EDHOC-Exporter interface. Security Context, using the EDHOC-Exporter interface.
From TH_3 and CIPHERTEXT_3, compute the input to the transcript hash From TH_3 and CIPHERTEXT_3, compute the input to the transcript hash
TH_4 = H( TH_3, CIPHERTEXT_3 ), as a CBOR Sequence of these 2 data TH_4 = H( TH_3, CIPHERTEXT_3 ), as a CBOR Sequence of these 2 data
items. items.
Input to calculate TH_4 (CBOR Sequence) (53 bytes) Input to calculate TH_4 (CBOR Sequence) (53 bytes)
58 20 b6 cd 80 4f c4 b9 d7 ca c5 02 ab d7 7c da 74 e4 1c b0 11 82 d7 cb 58 20 b6 cd 80 4f c4 b9 d7 ca c5 02 ab d7 7c da 74 e4 1c b0 11 82 d7 cb
skipping to change at page 94, line 36 skipping to change at page 96, line 4
c2 24 34 9d 9b 34 ca 8c c2 24 34 9d 9b 34 ca 8c
The client's OSCORE Sender ID is C_R and the server's OSCORE Sender The client's OSCORE Sender ID is C_R and the server's OSCORE Sender
ID is C_I. ID is C_I.
Client's OSCORE Sender ID (1 byte) Client's OSCORE Sender ID (1 byte)
00 00
Server's OSCORE Sender ID (1 byte) Server's OSCORE Sender ID (1 byte)
16 16
The AEAD Algorithm and the hash algorithm are the application AEAD The AEAD Algorithm and the hash algorithm are the application AEAD
and hash algorithms in the selected cipher suite. and hash algorithms in the selected cipher suite.
OSCORE AEAD Algorithm (int) OSCORE AEAD Algorithm (int)
10 10
OSCORE Hash Algorithm (int) OSCORE Hash Algorithm (int)
-16 -16
Appendix D. Applicability Template Appendix E. Applicability Template
This appendix contains an example of an applicability statement, see This appendix contains an example of an applicability statement, see
Section 3.7. Section 3.9.
For use of EDHOC in the XX protocol, the following assumptions are For use of EDHOC in the XX protocol, the following assumptions are
made on the parameters: made on the parameters:
* METHOD_CORR = 5 o METHOD = 1 (I uses signature key, R uses static DH key.)
- method = 1 (I uses signature key, R uses static DH key.)
- corr = 1 (CoAP Token or other transport data enables
correlation between message_1 and message_2.)
* EDHOC requests are expected by the server at /app1-edh, no o EDHOC requests are expected by the server at /app1-edh, no
Content-Format needed. Content-Format needed.
* C_1 = "null" is present to identify message_1 o CRED_I is an 802.1AR IDevID encoded as a C509 Certificate of type
* CRED_I is an 802.1AR IDevID encoded as a C509 Certificate of type
0 [I-D.ietf-cose-cbor-encoded-cert]. 0 [I-D.ietf-cose-cbor-encoded-cert].
- R acquires CRED_I out-of-band, indicated in EAD_1 * R acquires CRED_I out-of-band, indicated in EAD_1
- ID_CRED_I = {4: h''} is a kid with value empty byte string * ID_CRED_I = {4: h''} is a kid with value empty byte string
* CRED_R is a COSE_Key of type OKP as specified in Section 3.3.4. o CRED_R is a COSE_Key of type OKP as specified in Section 3.5.4.
- The CBOR map has parameters 1 (kty), -1 (crv), and -2 * The CBOR map has parameters 1 (kty), -1 (crv), and -2
(x-coordinate). (x-coordinate).
* ID_CRED_R = CRED_R o ID_CRED_R = CRED_R
* No use of message_4: the application sends protected messages from o No use of message_4: the application sends protected messages from
R to I. R to I.
* External authorization data is defined and processed as specified o External authorization data is defined and processed as specified
in [I-D.selander-ace-ake-authz]. in [I-D.selander-ace-ake-authz].
Appendix E. EDHOC Message Deduplication Appendix F. EDHOC Message Deduplication
EDHOC by default assumes that message duplication is handled by the EDHOC by default assumes that message duplication is handled by the
transport, in this section exemplified with CoAP. transport, in this section exemplified with CoAP.
Deduplication of CoAP messages is described in Section 4.5 of Deduplication of CoAP messages is described in Section 4.5 of
[RFC7252]. This handles the case when the same Confirmable (CON) [RFC7252]. This handles the case when the same Confirmable (CON)
message is received multiple times due to missing acknowledgement on message is received multiple times due to missing acknowledgement on
CoAP messaging layer. The recommended processing in [RFC7252] is CoAP messaging layer. The recommended processing in [RFC7252] is
that the duplicate message is acknowledged (ACK), but the received that the duplicate message is acknowledged (ACK), but the received
message is only processed once by the CoAP stack. message is only processed once by the CoAP stack.
Message deduplication is resource demanding and therefore not Message deduplication is resource demanding and therefore not
supported in all CoAP implementations. Since EDHOC is targeting supported in all CoAP implementations. Since EDHOC is targeting
constrained environments, it is desirable that EDHOC can optionally constrained environments, it is desirable that EDHOC can optionally
support transport layers which does not handle message duplication. support transport layers which does not handle message duplication.
Special care is needed to avoid issues with duplicate messages, see Special care is needed to avoid issues with duplicate messages, see
Section 5.2. Section 5.1.
The guiding principle here is similar to the deduplication processing The guiding principle here is similar to the deduplication processing
on CoAP messaging layer: a received duplicate EDHOC message SHALL NOT on CoAP messaging layer: a received duplicate EDHOC message SHALL NOT
result in a response consisting of another instance of the next EDHOC result in a response consisting of another instance of the next EDHOC
message. The result MAY be that a duplicate EDHOC response is sent, message. The result MAY be that a duplicate EDHOC response is sent,
provided it is still relevant with respect the current protocol provided it is still relevant with respect the current protocol
state. In any case, the received message MUST NOT be processed more state. In any case, the received message MUST NOT be processed more
than once in the same EDHOC session. This is called "EDHOC message than once in the same EDHOC session. This is called "EDHOC message
deduplication". deduplication".
An EDHOC implementation MAY store the previously sent EDHOC message An EDHOC implementation MAY store the previously sent EDHOC message
to be able to resend it. An EDHOC implementation MAY keep the to be able to resend it. An EDHOC implementation MAY keep the
protocol state to be able to recreate the previously sent EDHOC protocol state to be able to recreate the previously sent EDHOC
message and resend it. The previous message or protocol state MUST message and resend it. The previous message or protocol state MUST
NOT be kept longer than what is required for retransmission, for NOT be kept longer than what is required for retransmission, for
example, in the case of CoAP transport, no longer than the example, in the case of CoAP transport, no longer than the
EXCHANGE_LIFETIME (see Section 4.8.2 of [RFC7252]). EXCHANGE_LIFETIME (see Section 4.8.2 of [RFC7252]).
Note that the requirements in Section 5.2 still apply because Note that the requirements in Section 5.1 still apply because
duplicate messages are not processed by the EDHOC state machine: duplicate messages are not processed by the EDHOC state machine:
* EDHOC messages SHALL be processed according to the current o EDHOC messages SHALL be processed according to the current
protocol state. protocol state.
* Different instances of the same message MUST NOT be processed in o Different instances of the same message MUST NOT be processed in
one session. one session.
Appendix F. Change Log Appendix G. Transports Not Natively Providing Correlation
Protocols that do not natively provide full correlation between a
series of messages can send the C_I and C_R identifiers along as
needed.
The transport over CoAP (Appendix A.3) can serve as a blueprint for
other server-client protocols: The client prepends the C_x which the
server selected (or, for message 1, a sentinel null value which is
not a valid C_x) to any request message it sends. The server does
not send any such indicator, as responses are matched to request by
the client-server protocol design.
Protocols that do not provide any correlation at all can prescribe
prepending of the peer's chosen C_x to all messages.
Appendix H. Change Log
Main changes: Main changes:
* From -06 to -07: o From -07 to -08:
- Changed transcript hash definition for TH_2 and TH_3 * Prepended C_x moved from the EDHOC protocol itself to the
transport mapping
- Removed "EDHOC signature algorithm curve" from cipher suite * METHOD_CORR renamed to METHOD, corr removed
- New IANA registry "EDHOC Exporter Label" * Removed bstr_identifier and use bstr / int instead; C_x can now
be int without any implied bstr semantics
- New application defined parameter "context" in EDHOC-Exporter * Defined COSE header parameter 'kid2' with value type bstr / int
- Changed normative language for failure from MUST to SHOULD send for use with ID_CRED_x
* Updated message sizes
* New cipher suites with AES-GCM and ChaCha20 / Poly1305
* Changed from one- to two-byte identifier of CNSA compliant
suite
* Separate sections on transport and connection id with further
sub-structure
* Moved back key derivation for OSCORE from draft-ietf-core-
oscore-edhoc
* OSCORE and CoAP specific processing moved to new appendix
* Message 4 section moved to message processing section
o From -06 to -07:
* Changed transcript hash definition for TH_2 and TH_3
* Removed "EDHOC signature algorithm curve" from cipher suite
* New IANA registry "EDHOC Exporter Label"
* New application defined parameter "context" in EDHOC-Exporter
* Changed normative language for failure from MUST to SHOULD send
error error
- Made error codes non-negative and 0 for success * Made error codes non-negative and 0 for success
- Added detail on success error code * Added detail on success error code
- Aligned terminology "protocol instance" -> "session" * Aligned terminology "protocol instance" -> "session"
- New appendix on compact EC point representation * New appendix on compact EC point representation
- Added detail on use of ephemeral public keys * Added detail on use of ephemeral public keys
- Moved key derivation for OSCORE to draft-ietf-core-oscore-edhoc * Moved key derivation for OSCORE to draft-ietf-core-oscore-edhoc
- Additional security considerations * Additional security considerations
- Renamed "Auxililary Data" as "External Authorization Data" * Renamed "Auxililary Data" as "External Authorization Data"
- Added encrypted EAD_4 to message_4 * Added encrypted EAD_4 to message_4
* From -05 to -06: o From -05 to -06:
- New section 5.2 "Message Processing Outline" * New section 5.2 "Message Processing Outline"
- Optional inital byte C_1 = null in message_1 * Optional inital byte C_1 = null in message_1
- New format of error messages, table of error codes, IANA * New format of error messages, table of error codes, IANA
registry registry
- Change of recommendation transport of error in CoAP * Change of recommendation transport of error in CoAP
- Merge of content in 3.7 and appendix C into new section 3.7 * Merge of content in 3.7 and appendix C into new section 3.7
"Applicability Statement" "Applicability Statement"
- Requiring use of deterministic CBOR * Requiring use of deterministic CBOR
- New section on message deduplication
- New appendix containin all CDDL definitions * New section on message deduplication
- New appendix with change log * New appendix containin all CDDL definitions
- Removed section "Other Documents Referencing EDHOC" * New appendix with change log
- Clarifications based on review comments * Removed section "Other Documents Referencing EDHOC"
* Clarifications based on review comments
* From -04 to -05: o From -04 to -05:
- EDHOC-Rekey-FS -> EDHOC-KeyUpdate * EDHOC-Rekey-FS -> EDHOC-KeyUpdate
- Clarification of cipher suite negotiation * Clarification of cipher suite negotiation
- Updated security considerations * Updated security considerations
- Updated test vectors * Updated test vectors
- Updated applicability statement template * Updated applicability statement template
* From -03 to -04: o From -03 to -04:
- Restructure of section 1 * Restructure of section 1
- Added references to C509 Certificates * Added references to C509 Certificates
- Change in CIPHERTEXT_2 -> plaintext XOR KEYSTREAM_2 (test * Change in CIPHERTEXT_2 -> plaintext XOR KEYSTREAM_2 (test
vector not updated) vector not updated)
- "K_2e", "IV_2e" -> KEYSTREAM_2 * "K_2e", "IV_2e" -> KEYSTREAM_2
- Specified optional message 4 * Specified optional message 4
- EDHOC-Exporter-FS -> EDHOC-Rekey-FS * EDHOC-Exporter-FS -> EDHOC-Rekey-FS
- Less constrained devices SHOULD implement both suite 0 and 2 * Less constrained devices SHOULD implement both suite 0 and 2
- Clarification of error message * Clarification of error message
- Added exporter interface test vector * Added exporter interface test vector
* From -02 to -03: o From -02 to -03:
- Rearrangements of section 3 and beginning of section 4 * Rearrangements of section 3 and beginning of section 4
- Key derivation new section 4 * Key derivation new section 4
- Cipher suites 4 and 5 added * Cipher suites 4 and 5 added
- EDHOC-EXPORTER-FS - generate a new PRK_4x3m from an old one * EDHOC-EXPORTER-FS - generate a new PRK_4x3m from an old one
- Change in CIPHERTEXT_2 -> COSE_Encrypt0 without tag (no change * Change in CIPHERTEXT_2 -> COSE_Encrypt0 without tag (no change
to test vector) to test vector)
- Clarification of error message * Clarification of error message
- New appendix C applicability statement * New appendix C applicability statement
* From -01 to -02: o From -01 to -02:
- New section 1.2 Use of EDHOC * New section 1.2 Use of EDHOC
- Clarification of identities * Clarification of identities
- New section 4.3 clarifying bstr_identifier * New section 4.3 clarifying bstr_identifier
- Updated security considerations * Updated security considerations
- Updated text on cipher suite negotiation and key confirmation * Updated text on cipher suite negotiation and key confirmation
- Test vector for static DH * Test vector for static DH
* From -00 to -01: o From -00 to -01:
- Removed PSK method * Removed PSK method
- Removed references to certificate by value * Removed references to certificate by value
Acknowledgments Acknowledgments
The authors want to thank Alessandro Bruni, Karthikeyan Bhargavan, The authors want to thank Christian Amsuess, Alessandro Bruni,
Timothy Claeys, Martin Disch, Theis Groenbech Petersen, Dan Harkins, Karthikeyan Bhargavan, Timothy Claeys, Martin Disch, Theis Groenbech
Klaus Hartke, Russ Housley, Stefan Hristozov, Alexandros Krontiris, Petersen, Dan Harkins, Klaus Hartke, Russ Housley, Stefan Hristozov,
Ilari Liusvaara, Karl Norrman, Salvador Perez, Eric Rescorla, Michael Alexandros Krontiris, Ilari Liusvaara, Karl Norrman, Salvador Perez,
Richardson, Thorvald Sahl Joergensen, Jim Schaad, Carsten Schuermann, Eric Rescorla, Michael Richardson, Thorvald Sahl Joergensen, Jim
Ludwig Seitz, Stanislav Smyshlyaev, Valery Smyslov, Peter van der Schaad, Carsten Schuermann, Ludwig Seitz, Stanislav Smyshlyaev,
Stok, Rene Struik, Vaishnavi Sundararajan, Erik Thormarker, Marco Valery Smyslov, Peter van der Stok, Rene Struik, Vaishnavi
Tiloca, Michel Veillette, and Malisa Vucinic for reviewing and Sundararajan, Erik Thormarker, Marco Tiloca, Michel Veillette, and
commenting on intermediate versions of the draft. We are especially Malisa Vucinic for reviewing and commenting on intermediate versions
indebted to Jim Schaad for his continuous reviewing and of the draft. We are especially indebted to Jim Schaad for his
implementation of different versions of the draft. continuous reviewing and implementation of different versions of the
draft.
Work on this document has in part been supported by the H2020 project Work on this document has in part been supported by the H2020 project
SIFIS-Home (grant agreement 952652). SIFIS-Home (grant agreement 952652).
Authors' Addresses Authors' Addresses
Göran Selander Goeran Selander
Ericsson AB Ericsson AB
Email: goran.selander@ericsson.com Email: goran.selander@ericsson.com
John Preuss Mattsson
John Preuß Mattsson
Ericsson AB Ericsson AB
Email: john.mattsson@ericsson.com Email: john.mattsson@ericsson.com
Francesca Palombini Francesca Palombini
Ericsson AB Ericsson AB
Email: francesca.palombini@ericsson.com Email: francesca.palombini@ericsson.com
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