draft-ietf-ace-coap-est-18.txt   rfc9148.txt 
ACE P. van der Stok Internet Engineering Task Force (IETF) P. van der Stok
Internet-Draft Consultant Request for Comments: 9148 Consultant
Intended status: Standards Track P. Kampanakis Category: Standards Track P. Kampanakis
Expires: July 9, 2020 Cisco Systems ISSN: 2070-1721 Cisco Systems
M. Richardson M. Richardson
SSW SSW
S. Raza S. Raza
RISE SICS RISE Research Institutes of Sweden
January 6, 2020 April 2022
EST over secure CoAP (EST-coaps) EST-coaps: Enrollment over Secure Transport with the Secure Constrained
draft-ietf-ace-coap-est-18 Application Protocol
Abstract Abstract
Enrollment over Secure Transport (EST) is used as a certificate Enrollment over Secure Transport (EST) is used as a certificate
provisioning protocol over HTTPS. Low-resource devices often use the provisioning protocol over HTTPS. Low-resource devices often use the
lightweight Constrained Application Protocol (CoAP) for message lightweight Constrained Application Protocol (CoAP) for message
exchanges. This document defines how to transport EST payloads over exchanges. This document defines how to transport EST payloads over
secure CoAP (EST-coaps), which allows constrained devices to use secure CoAP (EST-coaps), which allows constrained devices to use
existing EST functionality for provisioning certificates. existing EST functionality for provisioning certificates.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on July 9, 2020. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9148.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7 2. Terminology
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. DTLS and Conformance to RFC 7925 Profiles
4. DTLS and conformance to RFC7925 profiles . . . . . . . . . . 7 4. Protocol Design
5. Protocol Design . . . . . . . . . . . . . . . . . . . . . . . 10 4.1. Discovery and URIs
5.1. Discovery and URIs . . . . . . . . . . . . . . . . . . . 10 4.2. Mandatory/Optional EST Functions
5.2. Mandatory/optional EST Functions . . . . . . . . . . . . 13 4.3. Payload Formats
5.3. Payload formats . . . . . . . . . . . . . . . . . . . . . 13 4.4. Message Bindings
5.4. Message Bindings . . . . . . . . . . . . . . . . . . . . 15 4.5. CoAP Response Codes
5.5. CoAP response codes . . . . . . . . . . . . . . . . . . . 15 4.6. Message Fragmentation
5.6. Message fragmentation . . . . . . . . . . . . . . . . . . 16 4.7. Delayed Responses
5.7. Delayed Responses . . . . . . . . . . . . . . . . . . . . 17 4.8. Server-Side Key Generation
5.8. Server-side Key Generation . . . . . . . . . . . . . . . 19 5. HTTPS-CoAPS Registrar
6. HTTPS-CoAPS Registrar . . . . . . . . . . . . . . . . . . . . 21 6. Parameters
7. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 23 7. Deployment Limitations
8. Deployment limitations . . . . . . . . . . . . . . . . . . . 23 8. IANA Considerations
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 8.1. Content-Formats Registry
9.1. Content-Format Registry . . . . . . . . . . . . . . . . . 24 8.2. Resource Type Registry
9.2. Resource Type registry . . . . . . . . . . . . . . . . . 24 8.3. Well-Known URIs Registry
9.3. Well-Known URIs Registry . . . . . . . . . . . . . . . . 25 9. Security Considerations
10. Security Considerations . . . . . . . . . . . . . . . . . . . 25 9.1. EST Server Considerations
10.1. EST server considerations . . . . . . . . . . . . . . . 25 9.2. HTTPS-CoAPS Registrar Considerations
10.2. HTTPS-CoAPS Registrar considerations . . . . . . . . . . 27 10. References
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 28 10.1. Normative References
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 10.2. Informative References
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 Appendix A. EST Messages to EST-coaps
13.1. Normative References . . . . . . . . . . . . . . . . . . 28 A.1. cacerts
13.2. Informative References . . . . . . . . . . . . . . . . . 30 A.2. enroll / reenroll
Appendix A. EST messages to EST-coaps . . . . . . . . . . . . . 32 A.3. serverkeygen
A.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 33 A.4. csrattrs
A.2. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 35 Appendix B. EST-coaps Block Message Examples
A.3. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 37 B.1. cacerts
A.4. csrattrs . . . . . . . . . . . . . . . . . . . . . . . . 39 B.2. enroll / reenroll
Appendix B. EST-coaps Block message examples . . . . . . . . . . 40 Appendix C. Message Content Breakdown
B.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 40 C.1. cacerts
B.2. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 44 C.2. enroll / reenroll
Appendix C. Message content breakdown . . . . . . . . . . . . . 45 C.3. serverkeygen
C.1. cacerts . . . . . . . . . . . . . . . . . . . . . . . . . 45 Acknowledgements
C.2. enroll / reenroll . . . . . . . . . . . . . . . . . . . . 46 Contributors
C.3. serverkeygen . . . . . . . . . . . . . . . . . . . . . . 48 Authors' Addresses
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 50
1. Change Log
EDNOTE: Remove this section before publication
-18
IESG Reviews fixes.
Removed spurious lines introduced in v-17 due to xml2rfc v3.
-17
v16 remnants by Ben K.
Typos.
-16
Updates to address Yaron S.'s Secdir review.
Updates to address David S.'s Gen-ART review.
-15
Updates to addressed Ben's AD follow up feedback.
-14
Updates to complete Ben's AD review feedback and discussions.
-13
Updates based on AD's review and discussions
Examples redone without password
-12
Updated section 5 based on Esko's comments and nits identified.
Nits and some clarifications for Esko's new review from 5/21/2019.
Nits and some clarifications for Esko's new review from 5/28/2019.
-11
Updated Server-side keygen to simplify motivation and added
paragraphs in Security considerations to point out that random
numbers are still needed (feedback from Hannes).
-10
Addressed WGLC comments
More consistent request format in the examples.
Explained root resource difference when there is resource
discovery
Clarified when the client is supposed to do discovery
Fixed nits and minor Option length inaccurracies in the examples.
-09
WGLC comments taken into account
consensus about discovery of content-format
added additional path for content-format selection
merged DTLS sections
-08
added application/pkix-cert Content-Format TBD287.
discovery text clarified
Removed text on ct negotiation in connection to multipart-core
removed text that duplicates or contradicts RFC7252 (thanks Klaus)
Stated that well-known/est is compulsory
Use of response codes clarified.
removed bugs: Max-Age and Content-Format Options in Request
Accept Option explained for est/skg and added in enroll example
Added second URI /skc for server-side key gen and a simple cert
(not PKCS#7)
Persistence of DTLS connection clarified.
Minor text fixes.
-07:
redone examples from scratch with openssl
Updated authors.
Added CoAP RST as a MAY for an equivalent to an HTTP 204 message.
Added serialization example of the /skg CBOR response.
Added text regarding expired IDevIDs and persistent DTLS
connection that will start using the Explicit TA Database in the
new DTLS connection.
Nits and fixes
Removed CBOR envelop for binary data
Replaced TBD8 with 62.
Added RFC8174 reference and text.
Clarified MTI for server-side key generation and Content-Formats.
Defined the /skg MTI (PKCS#8) and the cases where CMS encryption
will be used.
Moved Fragmentation section up because it was referenced in
sections above it.
-06:
clarified discovery section, by specifying that no discovery may
be needed for /.well-known/est URI.
added resource type values for IANA
added list of compulsory to implement and optional functions.
Fixed issues pointed out by the idnits tool.
Updated CoAP response codes section with more mappings between EST
HTTP codes and EST-coaps CoAP codes.
Minor updates to the MTI EST Functions section.
Moved Change Log section higher.
-05:
repaired again
TBD8 = 62 removed from C-F registration, to be done in CT draft.
-04:
Updated Delayed response section to reflect short and long delay
options.
-03:
Removed observe and simplified long waits
Repaired Content-Format specification
-02:
Added parameter discussion in section 8
Concluded Content-Format specification using multipart-ct draft
examples updated
-01:
Editorials done.
Redefinition of proxy to Registrar in Section 6. Explained better
the role of https-coaps Registrar, instead of "proxy"
Provide "observe" Option examples
extended block message example.
inserted new server key generation text in Section 5.8 and
motivated server key generation.
Broke down details for DTLS 1.3
New Media-Type uses CBOR array for multiple Content-Format
payloads
provided new Content-Format tables
new media format for IANA
-00
copied from vanderstok-ace-coap-04
2. Introduction 1. Introduction
"Classical" Enrollment over Secure Transport (EST) [RFC7030] is used "Classical" Enrollment over Secure Transport (EST) [RFC7030] is used
for authenticated/authorized endpoint certificate enrollment (and for authenticated/authorized endpoint certificate enrollment (and
optionally key provisioning) through a Certificate Authority (CA) or optionally key provisioning) through a Certification Authority (CA)
Registration Authority (RA). EST transports messages over HTTPS. or Registration Authority (RA). EST transports messages over HTTPS.
This document defines a new transport for EST based on the This document defines a new transport for EST based on the
Constrained Application Protocol (CoAP) since some Internet of Things Constrained Application Protocol (CoAP) since some Internet of Things
(IoT) devices use CoAP instead of HTTP. Therefore, this (IoT) devices use CoAP instead of HTTP. Therefore, this
specification utilizes DTLS [RFC6347] and CoAP [RFC7252] instead of specification utilizes DTLS [RFC6347] and CoAP [RFC7252] instead of
TLS [RFC8446] and HTTP [RFC7230]. TLS [RFC8446] and HTTP [RFC7230].
EST responses can be relatively large and for this reason this EST responses can be relatively large, and for this reason, this
specification also uses CoAP Block-Wise Transfer [RFC7959] to offer a specification also uses CoAP Block-Wise Transfer [RFC7959] to offer a
fragmentation mechanism of EST messages at the CoAP layer. fragmentation mechanism of EST messages at the CoAP layer.
This document also profiles the use of EST to only support This document also profiles the use of EST to support certificate-
certificate-based client authentication. HTTP Basic or Digest based client authentication only. Neither HTTP Basic nor Digest
authentication (as described in Section 3.2.3 of [RFC7030]) are not authentication (as described in Section 3.2.3 of [RFC7030]) is
supported. supported.
3. Terminology 2. Terminology
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
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
Many of the concepts in this document are taken from [RFC7030]. Many of the concepts in this document are taken from [RFC7030].
Consequently, much text is directly traceable to [RFC7030]. Consequently, much text is directly traceable to [RFC7030].
4. DTLS and conformance to RFC7925 profiles 3. DTLS and Conformance to RFC 7925 Profiles
This section describes how EST-coaps conforms to the profiles of low- This section describes how EST-coaps conforms to the profiles of low-
resource devices described in [RFC7925]. EST-coaps can transport resource devices described in [RFC7925]. EST-coaps can transport
certificates and private keys. Certificates are responses to certificates and private keys. Certificates are responses to
(re-)enrollment requests or requests for a trusted certificate list. (re-)enrollment requests or requests for a trusted certificate list.
Private keys can be transported as responses to a server-side key Private keys can be transported as responses to a server-side key
generation request as described in Section 4.4 of [RFC7030] (and generation request as described in Section 4.4 of [RFC7030] (and
subsections) and discussed in Section 5.8 of this document. subsections) and discussed in Section 4.8 of this document.
EST-coaps depends on a secure transport mechanism that secures the EST-coaps depends on a secure transport mechanism that secures the
exchanged CoAP messages. DTLS is one such secure protocol. No other exchanged CoAP messages. DTLS is one such secure protocol. No other
changes are necessary regarding the secure transport of EST messages. changes are necessary regarding the secure transport of EST messages.
+------------------------------------------------+ +------------------------------------------------+
| EST request/response messages | | EST request/response messages |
+------------------------------------------------+ +------------------------------------------------+
| CoAP for message transfer and signaling | | CoAP for message transfer and signaling |
+------------------------------------------------+ +------------------------------------------------+
| Secure Transport | | Secure Transport |
+------------------------------------------------+ +------------------------------------------------+
Figure 1: EST-coaps protocol layers Figure 1: EST-coaps Protocol Layers
In accordance with sections 3.3 and 4.4 of [RFC7925], the mandatory In accordance with Sections 3.3 and 4.4 of [RFC7925], the mandatory
cipher suite for DTLS in EST-coaps is cipher suite for DTLS in EST-coaps is
TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 [RFC7251]. Curve secp256r1 MUST TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 [RFC7251]. Curve secp256r1 MUST
be supported [RFC8422]; this curve is equivalent to the NIST P-256 be supported [RFC8422]; this curve is equivalent to the NIST P-256
curve. After the publication of [RFC7748], support for Curve25519 curve. After the publication of [RFC7748], support for Curve25519
will likely be required in the future by (D)TLS Profiles for the will likely be required in the future by (D)TLS profiles for the
Internet of Things [RFC7925]. Internet of Things [RFC7925].
DTLS 1.2 implementations must use the Supported Elliptic Curves and DTLS 1.2 implementations must use the Supported Elliptic Curves and
Supported Point Formats Extensions in [RFC8422]. Uncompressed point Supported Point Formats Extensions in [RFC8422]. Uncompressed point
format must also be supported. DTLS 1.3 [I-D.ietf-tls-dtls13] format must also be supported. DTLS 1.3 [RFC9147] implementations
implementations differ from DTLS 1.2 because they do not support differ from DTLS 1.2 because they do not support point format
point format negotiation in favor of a single point format for each negotiation in favor of a single point format for each curve. Thus,
curve. Thus, support for DTLS 1.3 does not mandate point format support for DTLS 1.3 does not mandate point format extensions and
extensions and negotiation. In addition, in DTLS 1.3 the Supported negotiation. In addition, in DTLS 1.3, the Supported Elliptic Curves
Elliptic Curves extension has been renamed to Supported Groups. extension has been renamed to Supported Groups.
CoAP was designed to avoid IP fragmentation. DTLS is used to secure CoAP was designed to avoid IP fragmentation. DTLS is used to secure
CoAP messages. However, fragmentation is still possible at the DTLS CoAP messages. However, fragmentation is still possible at the DTLS
layer during the DTLS handshake when using ECC ciphersuites. If layer during the DTLS handshake even when using Elliptic Curve
fragmentation is necessary, "DTLS provides a mechanism for Cryptography (ECC) cipher suites. If fragmentation is necessary,
fragmenting a handshake message over several records, each of which "DTLS provides a mechanism for fragmenting a handshake message over a
can be transmitted separately, thus avoiding IP fragmentation" number of records, each of which can be transmitted separately, thus
[RFC6347]. avoiding IP fragmentation" [RFC6347].
The authentication of the EST-coaps server by the EST-coaps client is The authentication of the EST-coaps server by the EST-coaps client is
based on certificate authentication in the DTLS handshake. The EST- based on certificate authentication in the DTLS handshake. The EST-
coaps client MUST be configured with at least an Implicit TA database coaps client MUST be configured with at least an Implicit Trust
which will enable the authentication of the server the first time Anchor database, which will enable the authentication of the server
before updating its trust anchor (Explicit TA) [RFC7030]. the first time before updating its trust anchor (Explicit TA)
[RFC7030].
The authentication of the EST-coaps client MUST be with a client The authentication of the EST-coaps client MUST be with a client
certificate in the DTLS handshake. This can either be certificate in the DTLS handshake. This can either be:
o a previously issued client certificate (e.g., an existing
* A previously issued client certificate (e.g., an existing
certificate issued by the EST CA); this could be a common case for certificate issued by the EST CA); this could be a common case for
simple re-enrollment of clients. simple re-enrollment of clients.
o a previously installed certificate (e.g., manufacturer IDevID * A previously installed certificate (e.g., manufacturer IDevID
[ieee802.1ar] or a certificate issued by some other party). [IEEE802.1AR] or a certificate issued by some other party).
IDevID's are expected to have a very long life, as long as the IDevID's are expected to have a very long life, as long as the
device, but under some conditions could expire. In that case, the device, but under some conditions could expire. In that case, the
server MAY authenticate a client certificate against its trust server MAY authenticate a client certificate against its trust
store although the certificate is expired (Section 10). store though the certificate is expired (Section 9).
EST-coaps supports the certificate types and Trust Anchors (TA) that EST-coaps supports the certificate types and TAs that are specified
are specified for EST in Section 3 of [RFC7030]. for EST in Section 3 of [RFC7030].
As described in Section 2.1 of [RFC5272] proof-of-identity refers to As described in Section 2.1 of [RFC5272], proof-of-identity refers to
a value that can be used to prove that an end-entity or client is in a value that can be used to prove that an end entity or client is in
the possession of and can use the private key corresponding to the the possession of and can use the private key corresponding to the
certified public key. Additionally, channel-binding information can certified public key. Additionally, channel-binding information can
link proof-of-identity with an established connection. Connection- link proof-of-identity with an established connection. Connection-
based proof-of-possession is OPTIONAL for EST-coaps clients and based proof-of-possession is OPTIONAL for EST-coaps clients and
servers. When proof-of-possession is desired, a set of actions are servers. When proof-of-possession is desired, a set of actions are
required regarding the use of tls-unique, described in Section 3.5 in required regarding the use of tls-unique, described in Section 3.5 of
[RFC7030]. The tls-unique information consists of the contents of [RFC7030]. The tls-unique information consists of the contents of
the first "Finished" message in the (D)TLS handshake between server the first Finished message in the (D)TLS handshake between server and
and client [RFC5929]. The client adds the "Finished" message as a client [RFC5929]. The client adds the Finished message as a
ChallengePassword in the attributes section of the PKCS#10 Request challengePassword in the attributes section of the PKCS #10
[RFC5967] to prove that the client is indeed in control of the CertificationRequest [RFC5967] to prove that the client is indeed in
private key at the time of the (D)TLS session establishment. control of the private key at the time of the (D)TLS session
establishment. In the case of handshake message fragmentation, if
proof-of-possession is desired, the Finished message added as the
challengePassword in the Certificate Signing Request (CSR) is
calculated as specified by (D)TLS. We summarize it here for
convenience. For DTLS 1.2, in the event of handshake message
fragmentation, the hash of the handshake messages used in the Message
Authentication Code (MAC) calculation of the Finished message must be
computed on each reassembled message, as if each message had not been
fragmented (Section 4.2.6 of [RFC6347]). The Finished message is
calculated as shown in Section 7.4.9 of [RFC5246].
In the case of handshake message fragmentation, if proof-of- For (D)TLS 1.3, Appendix C.5 of [RFC8446] describes the lack of
possession is desired, the Finished message added as the channel bindings similar to tls-unique. [TLS13-CHANNEL-BINDINGS] can
ChallengePassword in the CSR is calculated as specified by the DTLS be used instead to derive a 32-byte tls-exporter binding from the
standards. We summarize it here for convenience. For DTLS 1.2, in (D)TLS 1.3 master secret by using a PRF negotiated in the (D)TLS 1.3
the event of handshake message fragmentation, the Hash of the handshake, "EXPORTER-Channel-Binding" with no terminating NUL as the
handshake messages used in the MAC calculation of the Finished label, the ClientHello.random and ServerHello.random, and a zero-
message must be computed on each reassembled message, as if each length context string. When proof-of-possession is desired, the
message had not been fragmented (Section 4.2.6 of [RFC6347]). The client adds the tls-exporter value as a challengePassword in the
Finished message is calculated as shown in Section 7.4.9 of attributes section of the PKCS #10 CertificationRequest [RFC5967] to
[RFC5246]. Similarly, for DTLS 1.3, the Finished message must be prove that the client is indeed in control of the private key at the
computed as if each handshake message had been sent as a single time of the (D)TLS session establishment.
fragment (Section 5.8 of [I-D.ietf-tls-dtls13]) following the
algorithm described in 4.4.4 of [RFC8446].
In a constrained CoAP environment, endpoints can't always afford to In a constrained CoAP environment, endpoints can't always afford to
establish a DTLS connection for every EST transaction. An EST-coaps establish a DTLS connection for every EST transaction. An EST-coaps
DTLS connection MAY remain open for sequential EST transactions, DTLS connection MAY remain open for sequential EST transactions,
which was not the case with [RFC7030]. For example, if a /crts which was not the case with [RFC7030]. For example, if a /crts
request is followed by a /sen request, both can use the same request is followed by a /sen request, both can use the same
authenticated DTLS connection. However, when a /crts request is authenticated DTLS connection. However, when a /crts request is
included in the set of sequential EST transactions, some additional included in the set of sequential EST transactions, some additional
security considerations apply regarding the use of the Implicit and security considerations apply regarding the use of the Implicit and
Explicit TA database as explained in Section 10.1. Explicit TA database as explained in Section 9.1.
Given that after a successful enrollment, it is more likely that a Given that after a successful enrollment, it is more likely that a
new EST transaction will not take place for a significant amount of new EST transaction will not take place for a significant amount of
time, the DTLS connections SHOULD only be kept alive for EST messages time, the DTLS connections SHOULD only be kept alive for EST messages
that are relatively close to each other. These could include a /sen that are relatively close to each other. These could include a /sen
immediatelly following a /crts when a device is getting bootstrapped. immediately following a /crts when a device is getting bootstrapped.
In some cases, like NAT rebinding, keeping the state of a connection In some cases, like NAT rebinding, keeping the state of a connection
is not possible when devices sleep for extended periods of time. In is not possible when devices sleep for extended periods of time. In
such occasions, [I-D.ietf-tls-dtls-connection-id] negotiates a such occasions, [RFC9146] negotiates a connection ID that can
connection ID that can eliminate the need for new handshake and its eliminate the need for a new handshake and its additional cost; or,
additional cost; or DTLS session resumption provides a less costly DTLS session resumption provides a less costly alternative than
alternative than re-doing a full DTLS handshake. redoing a full DTLS handshake.
5. Protocol Design 4. Protocol Design
EST-coaps uses CoAP to transfer EST messages, aided by Block-Wise EST-coaps uses CoAP to transfer EST messages, aided by Block-Wise
Transfer [RFC7959] to avoid IP fragmentation. The use of Blocks for Transfer [RFC7959], to avoid IP fragmentation. The use of blocks for
the transfer of larger EST messages is specified in Section 5.6. the transfer of larger EST messages is specified in Section 4.6.
Figure 1 shows the layered EST-coaps architecture. Figure 1 shows the layered EST-coaps architecture.
The EST-coaps protocol design follows closely the EST design. The The EST-coaps protocol design follows closely the EST design. The
supported message types in EST-coaps are: supported message types in EST-coaps are:
o CA certificate retrieval needed to receive the complete set of CA * CA certificate retrieval needed to receive the complete set of CA
certificates. certificates.
o Simple enroll and re-enroll for a CA to sign client identity * Simple enroll and re-enroll for a CA to sign client identity
public key. public keys.
o Certificate Signing Request (CSR) attribute messages that informs * Certificate Signing Request (CSR) attribute messages that informs
the client of the fields to include in a CSR. the client of the fields to include in a CSR.
o Server-side key generation messages to provide a client identity * Server-side key generation messages to provide a client identity
private key when the client chooses so. private key when the client chooses so.
While [RFC7030] permits a number of the EST functions to be used While [RFC7030] permits a number of the EST functions to be used
without authentication, this specification requires that the client without authentication, this specification requires that the client
MUST be authenticated for all functions. MUST be authenticated for all functions.
5.1. Discovery and URIs 4.1. Discovery and URIs
EST-coaps is targeted for low-resource networks with small packets. EST-coaps is targeted for low-resource networks with small packets.
Two types of installations are possible: (1) rigid ones, where the Two types of installations are possible: (1) a rigid one, where the
address and the supported functions of the EST server(s) are known, address and the supported functions of the EST server(s) are known,
and (2) a flexible one, where the EST server and its supported and (2) a flexible one, where the EST server and its supported
functions need to be discovered. functions need to be discovered.
For both types of installations, saving header space is important and For both types of installations, saving header space is important and
short EST-coaps URIs are specified in this document. These URIs are short EST-coaps URIs are specified in this document. These URIs are
shorter than the ones in [RFC7030]. Two example EST-coaps resource shorter than the ones in [RFC7030]. Two example EST-coaps resource
path names are: path names are:
coaps://example.com:<port>/.well-known/est/<short-est> coaps://example.com:<port>/.well-known/est/<short-est>
skipping to change at page 11, line 27 skipping to change at line 315
to the appropriate certificate profile. Implementers should consider to the appropriate certificate profile. Implementers should consider
using short labels to minimize transmission overhead. using short labels to minimize transmission overhead.
The EST-coaps server URIs, obtained through discovery of the EST- The EST-coaps server URIs, obtained through discovery of the EST-
coaps resource(s) as shown below, are of the form: coaps resource(s) as shown below, are of the form:
coaps://example.com:<port>/<root-resource>/<short-est> coaps://example.com:<port>/<root-resource>/<short-est>
coaps://example.com:<port>/<root-resource>/ArbitraryLabel/<short-est> coaps://example.com:<port>/<root-resource>/ArbitraryLabel/<short-est>
Figure 5 in Section 3.2.2 of [RFC7030] enumerates the operations and Figure 5 in Section 3.2.2 of [RFC7030] enumerates the operations and
corresponding paths which are supported by EST. Table 1 provides the corresponding paths that are supported by EST. Table 1 provides the
mapping from the EST URI path to the shorter EST-coaps URI path. mapping from the EST URI path to the shorter EST-coaps URI path.
+-------------------+-------------------------------+ +=================+==============================+
| EST | EST-coaps | | EST | EST-coaps |
+-------------------+-------------------------------+ +=================+==============================+
| /cacerts | /crts | | /cacerts | /crts |
| /simpleenroll | /sen | +-----------------+------------------------------+
| /simplereenroll | /sren | | /simpleenroll | /sen |
| /serverkeygen | /skg (PKCS#7) | +-----------------+------------------------------+
| /serverkeygen | /skc (application/pkix-cert) | | /simplereenroll | /sren |
| /csrattrs | /att | +-----------------+------------------------------+
+-------------------+-------------------------------+ | /serverkeygen | /skg (PKCS #7) |
+-----------------+------------------------------+
| /serverkeygen | /skc (application/pkix-cert) |
+-----------------+------------------------------+
| /csrattrs | /att |
+-----------------+------------------------------+
Table 1: Short EST-coaps URI path Table 1: Short EST-coaps URI Path
The /skg message is the EST /serverkeygen equivalent where the client The /skg message is the EST /serverkeygen equivalent where the client
requests a certificate in PKCS#7 format and a private key. If the requests a certificate in PKCS #7 format and a private key. If the
client prefers a single application/pkix-cert certificate instead of client prefers a single application/pkix-cert certificate instead of
PKCS#7, it will make an /skc request. In both cases (i.e., /skg, PKCS #7, it will make an /skc request. In both cases (i.e., /skg,
/skc) a private key MUST be returned. /skc), a private key MUST be returned.
Clients and servers MUST support the short resource EST-coaps URIs. Clients and servers MUST support the short resource EST-coaps URIs.
In the context of CoAP, the presence and location of (path to) the In the context of CoAP, the presence and location of (path to) the
EST resources are discovered by sending a GET request to "/.well- EST resources are discovered by sending a GET request to "/.well-
known/core" including a resource type (RT) parameter with the value known/core" including a resource type (RT) parameter with the value
"ace.est*" [RFC6690]. The example below shows the discovery over "ace.est*" [RFC6690]. The example below shows the discovery over
CoAPS of the presence and location of EST-coaps resources. Linefeeds CoAPS of the presence and location of EST-coaps resources. Linefeeds
are included only for readability. are included only for readability.
REQ: GET /.well-known/core?rt=ace.est* REQ: GET /.well-known/core?rt=ace.est*
RES: 2.05 Content RES: 2.05 Content
</est/crts>;rt="ace.est.crts";ct="281 TBD287", </est/crts>;rt="ace.est.crts";ct="281 287",
</est/sen>;rt="ace.est.sen";ct="281 TBD287", </est/sen>;rt="ace.est.sen";ct="281 287",
</est/sren>;rt="ace.est.sren";ct="281 TBD287", </est/sren>;rt="ace.est.sren";ct="281 287",
</est/att>;rt="ace.est.att";ct=285, </est/att>;rt="ace.est.att";ct=285,
</est/skg>;rt="ace.est.skg";ct=62, </est/skg>;rt="ace.est.skg";ct=62,
</est/skc>;rt="ace.est.skc";ct=62 </est/skc>;rt="ace.est.skc";ct=62
The first three lines, describing ace.est.crts, ace.est.sen, and The first three lines, describing ace.est.crts, ace.est.sen, and
ace.est.sren, of the discovery response above MUST be returned if the ace.est.sren, of the discovery response above MUST be returned if the
server supports resource discovery. The last three lines are only server supports resource discovery. The last three lines are only
included if the corresponding EST functions are implemented (see included if the corresponding EST functions are implemented (see
Table 2). The Content-Formats in the response allow the client to Table 2). The Content-Formats in the response allow the client to
request one that is supported by the server. These are the values request one that is supported by the server. These are the values
that would be sent in the client request with an Accept option. that would be sent in the client request with an Accept Option.
Discoverable port numbers can be returned in the response payload. Discoverable port numbers can be returned in the response payload.
An example response payload for non-default CoAPS server port 61617 An example response payload for non-default CoAPS server port 61617
follows below. Linefeeds are included only for readability. follows below. Linefeeds are included only for readability.
REQ: GET /.well-known/core?rt=ace.est* REQ: GET /.well-known/core?rt=ace.est*
RES: 2.05 Content RES: 2.05 Content
<coaps://[2001:db8:3::123]:61617/est/crts>;rt="ace.est.crts"; <coaps://[2001:db8:3::123]:61617/est/crts>;rt="ace.est.crts";
ct="281 TBD287", ct="281 287",
<coaps://[2001:db8:3::123]:61617/est/sen>;rt="ace.est.sen"; <coaps://[2001:db8:3::123]:61617/est/sen>;rt="ace.est.sen";
ct="281 TBD287", ct="281 287",
<coaps://[2001:db8:3::123]:61617/est/sren>;rt="ace.est.sren"; <coaps://[2001:db8:3::123]:61617/est/sren>;rt="ace.est.sren";
ct="281 TBD287", ct="281 287",
<coaps://[2001:db8:3::123]:61617/est/att>;rt="ace.est.att"; <coaps://[2001:db8:3::123]:61617/est/att>;rt="ace.est.att";
ct=285, ct=285,
<coaps://[2001:db8:3::123]:61617/est/skg>;rt="ace.est.skg"; <coaps://[2001:db8:3::123]:61617/est/skg>;rt="ace.est.skg";
ct=62, ct=62,
<coaps://[2001:db8:3::123]:61617/est/skc>;rt="ace.est.skc"; <coaps://[2001:db8:3::123]:61617/est/skc>;rt="ace.est.skc";
ct=62 ct=62
The server MUST support the default /.well-known/est root resource. The server MUST support the default /.well-known/est root resource.
The server SHOULD support resource discovery when it supports non- The server SHOULD support resource discovery when it supports non-
default URIs (like /est or /est/ArbitraryLabel) or ports. The client default URIs (like /est or /est/ArbitraryLabel) or ports. The client
SHOULD use resource discovery when it is unaware of the available SHOULD use resource discovery when it is unaware of the available
EST-coaps resources. EST-coaps resources.
Throughout this document the example root resource of /est is used. Throughout this document, the example root resource of /est is used.
5.2. Mandatory/optional EST Functions 4.2. Mandatory/Optional EST Functions
This specification contains a set of required-to-implement functions, This specification contains a set of required-to-implement functions,
optional functions, and not specified functions. The unspecified optional functions, and not-specified functions. The unspecified
functions are deemed too expensive for low-resource devices in functions are deemed too expensive for low-resource devices in
payload and calculation times. payload and calculation times.
Table 2 specifies the mandatory-to-implement or optional Table 2 specifies the mandatory-to-implement or optional
implementation of the EST-coaps functions. Discovery of the implementation of the EST-coaps functions. Discovery of the
existence of optional functions is described in Section 5.1. existence of optional functions is described in Section 4.1.
+-------------------+--------------------------+ +=================+==========================+
| EST Functions | EST-coaps implementation | | EST Functions | EST-coaps Implementation |
+-------------------+--------------------------+ +=================+==========================+
| /cacerts | MUST | | /cacerts | MUST |
| /simpleenroll | MUST | +-----------------+--------------------------+
| /simplereenroll | MUST | | /simpleenroll | MUST |
| /fullcmc | Not specified | +-----------------+--------------------------+
| /serverkeygen | OPTIONAL | | /simplereenroll | MUST |
| /csrattrs | OPTIONAL | +-----------------+--------------------------+
+-------------------+--------------------------+ | /fullcmc | Not specified |
+-----------------+--------------------------+
| /serverkeygen | OPTIONAL |
+-----------------+--------------------------+
| /csrattrs | OPTIONAL |
+-----------------+--------------------------+
Table 2: List of EST-coaps functions Table 2: List of EST-coaps Functions
5.3. Payload formats 4.3. Payload Formats
EST-coaps is designed for low-resource devices and hence does not EST-coaps is designed for low-resource devices; hence, it does not
need to send Base64-encoded data. Simple binary is more efficient need to send Base64-encoded data. Simple binary is more efficient
(30% smaller payload for DER-encoded ASN.1) and well supported by (30% smaller payload for DER-encoded ASN.1) and well supported by
CoAP. Thus, the payload for a given Media-Type follows the ASN.1 CoAP. Thus, the payload for a given media type follows the ASN.1
structure of the Media-Type and is transported in binary format. structure of the media type and is transported in binary format.
The Content-Format (HTTP Content-Type equivalent) of the CoAP message The Content-Format (HTTP Content-Type equivalent) of the CoAP message
determines which EST message is transported in the CoAP payload. The determines which EST message is transported in the CoAP payload. The
Media-Types specified in the HTTP Content-Type header field media types specified in the HTTP Content-Type header field
(Section 3.2.2 of [RFC7030]) are specified by the Content-Format (Section 3.2.4 of [RFC7030]) are specified by the Content-Format
Option (12) of CoAP. The combination of URI-Path and Content-Format Option (12) of CoAP. The combination of URI-Path and Content-Format
in EST-coaps MUST map to an allowed combination of URI and Media-Type in EST-coaps MUST map to an allowed combination of URI and media type
in EST. The required Content-Formats for these requests and response in EST. The required Content-Formats for these requests and response
messages are defined in Section 9.1. The CoAP response codes are messages are defined in Section 8.1. The CoAP response codes are
defined in Section 5.5. defined in Section 4.5.
Content-Format TBD287 can be used in place of 281 to carry a single Content-Format 287 can be used in place of 281 to carry a single
certificate instead of a PKCS#7 container in a /crts, /sen, /sren or certificate instead of a PKCS #7 container in a /crts, /sen, /sren,
/skg response. Content-Format 281 MUST be supported by EST-coaps or /skg response. Content-Format 281 MUST be supported by EST-coaps
servers. Servers MAY also support Content-Format TBD287. It is up servers. Servers MAY also support Content-Format 287. It is up to
to the client to support only Content-Format 281, TBD287 or both. the client to support only Content-Format 281, 287 or both. The
The client will use a COAP Accept Option in the request to express client will use a CoAP Accept Option in the request to express the
the preferred response Content-Format. If an Accept Option is not preferred response Content-Format. If an Accept Option is not
included in the request, the client is not expressing any preference included in the request, the client is not expressing any preference
and the server SHOULD choose format 281. and the server SHOULD choose format 281.
Content-Format 286 is used in /sen, /sren and /skg requests and 285 Content-Format 286 is used in /sen, /sren, and /skg requests and 285
in /att responses. in /att responses.
A representation with Content-Format identifier 62 contains a A representation with Content-Format identifier 62 contains a
collection of representations along with their respective Content- collection of representations along with their respective Content-
Format. The Content-Format identifies the Media-Type application/ Format. The Content-Format identifies the media type application/
multipart-core specified in [I-D.ietf-core-multipart-ct]. For multipart-core specified in [RFC8710]. For example, a collection,
example, a collection, containing two representations in response to containing two representations in response to an EST-coaps server-
a EST-coaps server-side key generation /skg request, could include a side key generation /skg request, could include a private key in PKCS
private key in PKCS#8 [RFC5958] with Content-Format identifier 284 #8 [RFC5958] with Content-Format identifier 284 (0x011C) and a single
(0x011C) and a single certificate in a PKCS#7 container with Content- certificate in a PKCS #7 container with Content-Format identifier 281
Format identifier 281 (0x0119). Such a collection would look like (0x0119). Such a collection would look like
[284,h'0123456789abcdef', 281,h'fedcba9876543210'] in diagnostic CBOR [284,h'0123456789abcdef', 281,h'fedcba9876543210'] in diagnostic
notation. The serialization of such CBOR content would be Concise Binary Object Representation (CBOR) notation. The
serialization of such CBOR content would be:
84 # array(4) 84 # array(4)
19 011C # unsigned(284) 19 011C # unsigned(284)
48 # bytes(8) 48 # bytes(8)
0123456789ABCDEF # "\x01#Eg\x89\xAB\xCD\xEF" 0123456789ABCDEF # "\x01#Eg\x89\xAB\xCD\xEF"
19 0119 # unsigned(281) 19 0119 # unsigned(281)
48 # bytes(8) 48 # bytes(8)
FEDCBA9876543210 # "\xFE\xDC\xBA\x98vT2\x10" FEDCBA9876543210 # "\xFE\xDC\xBA\x98vT2\x10"
Multipart /skg response serialization Figure 2: Multipart /skg Response Serialization
When the client makes an /skc request the certificate returned with When the client makes an /skc request, the certificate returned with
the private key is a single X.509 certificate (not a PKCS#7 the private key is a single X.509 certificate (not a PKCS #7
container) with Content-Format identifier TBD287 (0x011F) instead of container) with Content-Format identifier 287 (0x011F) instead of
281. In cases where the private key is encrypted with CMS (as 281. In cases where the private key is encrypted with Cryptographic
explained in Section 5.8) the Content-Format identifier is 280 Message Syntax (CMS) (as explained in Section 4.8), the Content-
(0x0118) instead of 284. The content format used in the response is Format identifier is 280 (0x0118) instead of 284. The Content-Format
summarized in Table 3. used in the response is summarized in Table 3.
+----------+-----------------+-----------------+ +==========+==================+==================+
| Function | Response part 1 | Response part 2 | | Function | Response, Part 1 | Response, Part 2 |
+----------+-----------------+-----------------+ +==========+==================+==================+
| /skg | 284 | 281 | | /skg | 284 | 281 |
| /skc | 280 | TBD287 | +----------+------------------+------------------+
+----------+-----------------+-----------------+ | /skc | 280 | 287 |
+----------+------------------+------------------+
Table 3: response content formats for skg and skc Table 3: Response Content-Formats for /skg and
/skc
The key and certificate representations are DER-encoded ASN.1, in its The key and certificate representations are DER-encoded ASN.1, in its
native binary form. An example is shown in Appendix A.3. binary form. An example is shown in Appendix A.3.
5.4. Message Bindings 4.4. Message Bindings
The general EST-coaps message characteristics are: The general EST-coaps message characteristics are:
o EST-coaps servers sometimes need to provide delayed responses * EST-coaps servers sometimes need to provide delayed responses,
which are preceded by an immediately returned empty ACK or an ACK which are preceded by an immediately returned empty ACK or an ACK
containing response code 5.03 as explained in Section 5.7. Thus, containing response code 5.03 as explained in Section 4.7. Thus,
it is RECOMMENDED for implementers to send EST-coaps requests in it is RECOMMENDED for implementers to send EST-coaps requests in
confirmable CON CoAP messages. Confirmable (CON) CoAP messages.
o The CoAP Options used are Uri-Host, Uri-Path, Uri-Port, Content- * The CoAP Options used are Uri-Host, Uri-Path, Uri-Port, Content-
Format, Block1, Block2, and Accept. These CoAP Options are used Format, Block1, Block2, and Accept. These CoAP Options are used
to communicate the HTTP fields specified in the EST REST messages. to communicate the HTTP fields specified in the EST REST messages.
The Uri-host and Uri-Port Options can be omitted from the COAP The Uri-host and Uri-Port Options can be omitted from the CoAP
message sent on the wire. When omitted, they are logically message sent on the wire. When omitted, they are logically
assumed to be the transport protocol destination address and port assumed to be the transport protocol destination address and port,
respectively. Explicit Uri-Host and Uri-Port Options are respectively. Explicit Uri-Host and Uri-Port Options are
typically used when an endpoint hosts multiple virtual servers and typically used when an endpoint hosts multiple virtual servers and
uses the Options to route the requests accordingly. Other COAP uses the Options to route the requests accordingly. Other CoAP
Options should be handled in accordance with [RFC7252]. Options should be handled in accordance with [RFC7252].
o EST URLs are HTTPS based (https://), in CoAP these are assumed to * EST URLs are HTTPS based (https://); in CoAP, these are assumed to
be translated to CoAPS (coaps://) be translated to CoAPS (coaps://).
Table 1 provides the mapping from the EST URI path to the EST-coaps Table 1 provides the mapping from the EST URI path to the EST-coaps
URI path. Appendix A includes some practical examples of EST URI path. Appendix A includes some practical examples of EST
messages translated to CoAP. messages translated to CoAP.
5.5. CoAP response codes 4.5. CoAP Response Codes
Section 5.9 of [RFC7252] and Section 7 of [RFC8075] specify the Section 5.9 of [RFC7252] and Section 7 of [RFC8075] specify the
mapping of HTTP response codes to CoAP response codes. The success mapping of HTTP response codes to CoAP response codes. The success
code in response to an EST-coaps GET request (/crts, /att), is 2.05. code in response to an EST-coaps GET request (/crts, /att) is 2.05.
Similarly, 2.04 is used in successful response to EST-coaps POST Similarly, 2.04 is used in successful response to EST-coaps POST
requests (/sen, /sren, /skg, /skc). requests (/sen, /sren, /skg, /skc).
EST makes use of HTTP 204 or 404 responses when a resource is not EST makes use of HTTP 204 or 404 responses when a resource is not
available for the client. In EST-coaps 2.04 is used in response to a available for the client. In EST-coaps, 2.04 is used in response to
POST (/sen, /sren, /skg, /skc). 4.04 is used when the resource is not a POST (/sen, /sren, /skg, /skc). 4.04 is used when the resource is
available for the client. not available for the client.
HTTP response code 202 with a Retry-After header field in [RFC7030] HTTP response code 202 with a Retry-After header field in [RFC7030]
has no equivalent in CoAP. HTTP 202 with Retry-After is used in EST has no equivalent in CoAP. HTTP 202 with Retry-After is used in EST
for delayed server responses. Section 5.7 specifies how EST-coaps for delayed server responses. Section 4.7 specifies how EST-coaps
handles delayed messages with 5.03 responses with a Max-Age Option. handles delayed messages with 5.03 responses with a Max-Age Option.
Additionally, EST's HTTP 400, 401, 403, 404 and 503 status codes have Additionally, EST's HTTP 400, 401, 403, 404, and 503 status codes
their equivalent CoAP 4.00, 4.01, 4.03, 4.04 and 5.03 response codes have their equivalent CoAP 4.00, 4.01, 4.03, 4.04, and 5.03 response
in EST-coaps. Table 4 summarizes the EST-coaps response codes. codes in EST-coaps. Table 4 summarizes the EST-coaps response codes.
+-----------------+-----------------+-------------------------------+ +=============+=========================+==========================+
| operation | EST-coaps | Description | | Operation | EST-coaps Response Code | Description |
| | response code | | +=============+=========================+==========================+
+-----------------+-----------------+-------------------------------+ | /crts, /att | 2.05 | Success. Certs included |
| /crts, /att | 2.05 | Success. Certs included in | | | | in the response payload. |
| | | the response payload. | +-------------+-------------------------+--------------------------+
| | 4.xx / 5.xx | Failure. | | | 4.xx / 5.xx | Failure. |
| /sen, /skg, | 2.04 | Success. Cert included in the | +-------------+-------------------------+--------------------------+
| /sren, /skc | | response payload. | | /sen, /skg, | 2.04 | Success. Cert included |
| | 5.03 | Retry in Max-Age Option time. | | /sren, /skc | | in the response payload. |
| | 4.xx / 5.xx | Failure. | +-------------+-------------------------+--------------------------+
+-----------------+-----------------+-------------------------------+ | | 5.03 | Retry in Max-Age Option |
| | | time. |
+-------------+-------------------------+--------------------------+
| | 4.xx / 5.xx | Failure. |
+-------------+-------------------------+--------------------------+
Table 4: EST-coaps response codes Table 4: EST-coaps Response Codes
5.6. Message fragmentation 4.6. Message Fragmentation
DTLS defines fragmentation only for the handshake and not for secure DTLS defines fragmentation only for the handshake and not for secure
data exchange (DTLS records). [RFC6347] states that to avoid using data exchange (DTLS records). [RFC6347] states that to avoid using
IP fragmentation, which involves error-prone datagram reconstitution, IP fragmentation, which involves error-prone datagram reconstitution,
invokers of the DTLS record layer should size DTLS records so that invokers of the DTLS record layer should size DTLS records so that
they fit within any Path MTU estimates obtained from the record they fit within any Path MTU estimates obtained from the record
layer. In addition, invokers residing on a 6LoWPAN over IEEE layer. In addition, invokers residing on 6LoWPAN (IPv6 over Low-
802.15.4 [ieee802.15.4] network are recommended to size CoAP messages Power Wireless Personal Area Networks) over IEEE 802.15.4 networks
such that each DTLS record will fit within one or two IEEE 802.15.4 [IEEE802.15.4] are recommended to size CoAP messages such that each
frames. DTLS record will fit within one or two IEEE 802.15.4 frames.
That is not always possible in EST-coaps. Even though ECC That is not always possible in EST-coaps. Even though ECC
certificates are small in size, they can vary greatly based on certificates are small in size, they can vary greatly based on
signature algorithms, key sizes, and Object Identifier (OID) fields signature algorithms, key sizes, and Object Identifier (OID) fields
used. For 256-bit curves, common ECDSA cert sizes are 500-1000 bytes used. For 256-bit curves, common Elliptic Curve Digital Signature
which could fluctuate further based on the algorithms, OIDs, Subject Algorithm (ECDSA) cert sizes are 500-1000 bytes, which could
Alternative Names (SAN) and cert fields. For 384-bit curves, ECDSA fluctuate further based on the algorithms, OIDs, Subject Alternative
Names (SANs), and cert fields. For 384-bit curves, ECDSA
certificates increase in size and can sometimes reach 1.5KB. certificates increase in size and can sometimes reach 1.5KB.
Additionally, there are times when the EST cacerts response from the Additionally, there are times when the EST cacerts response from the
server can include multiple certificates that amount to large server can include multiple certificates that amount to large
payloads. Section 4.6 of CoAP [RFC7252] describes the possible payloads. Section 4.6 of [RFC7252] (CoAP) describes the possible
payload sizes: "if nothing is known about the size of the headers, payload sizes: "if nothing is known about the size of the headers,
good upper bounds are 1152 bytes for the message size and 1024 bytes good upper bounds are 1152 bytes for the message size and 1024 bytes
for the payload size". Section 4.6 of [RFC7252] also suggests that for the payload size". Section 4.6 of [RFC7252] also suggests that
IPv4 implementations may want to limit themselves to more IPv4 implementations may want to limit themselves to more
conservative IPv4 datagram sizes such as 576 bytes. Even with ECC, conservative IPv4 datagram sizes such as 576 bytes. Even with ECC,
EST-coaps messages can still exceed MTU sizes on the Internet or EST-coaps messages can still exceed MTU sizes on the Internet or
6LoWPAN [RFC4919] (Section 2 of [RFC7959]). EST-coaps needs to be 6LoWPAN [RFC4919] (Section 2 of [RFC7959]). EST-coaps needs to be
able to fragment messages into multiple DTLS datagrams. able to fragment messages into multiple DTLS datagrams.
To perform fragmentation in CoAP, [RFC7959] specifies the Block1 To perform fragmentation in CoAP, [RFC7959] specifies the Block1
Option for fragmentation of the request payload and the Block2 Option Option for fragmentation of the request payload and the Block2 Option
for fragmentation of the return payload of a CoAP flow. As explained for fragmentation of the return payload of a CoAP flow. As explained
in Section 1 of [RFC7959], block-wise transfers should be used in in Section 1 of [RFC7959], block-wise transfers should be used in
Confirmable CoAP messages to avoid the exacerbation of lost blocks. Confirmable CoAP messages to avoid the exacerbation of lost blocks.
EST-coaps servers MUST implement Block1 and Block2. EST-coaps EST-coaps servers MUST implement Block1 and Block2. EST-coaps
clients MUST implement Block2. EST-coaps clients MUST implement clients MUST implement Block2. EST-coaps clients MUST implement
Block1 only if they are expecting to send EST-coaps requests with a Block1 only if they are expecting to send EST-coaps requests with a
packet size that exceeds the Path MTU. packet size that exceeds the path MTU.
[RFC7959] also defines Size1 and Size2 Options to provide size [RFC7959] also defines Size1 and Size2 Options to provide size
information about the resource representation in a request and information about the resource representation in a request and
response. EST-client and server MAY support Size1 and Size2 Options. response. The EST-coaps client and server MAY support Size1 and
Size2 Options.
Examples of fragmented EST-coaps messages are shown in Appendix B. Examples of fragmented EST-coaps messages are shown in Appendix B.
5.7. Delayed Responses 4.7. Delayed Responses
Server responses can sometimes be delayed. According to Server responses can sometimes be delayed. According to
Section 5.2.2 of [RFC7252], a slow server can acknowledge the request Section 5.2.2 of [RFC7252], a slow server can acknowledge the request
and respond later with the requested resource representation. In and respond later with the requested resource representation. In
particular, a slow server can respond to an EST-coaps enrollment particular, a slow server can respond to an EST-coaps enrollment
request with an empty ACK with code 0.00, before sending the request with an empty ACK with code 0.00 before sending the
certificate to the client after a short delay. If the certificate certificate to the client after a short delay. If the certificate
response is large, the server will need more than one Block2 block to response is large, the server will need more than one Block2 block to
transfer it. transfer it.
This situation is shown in Figure 2. The client sends an enrollment This situation is shown in Figure 3. The client sends an enrollment
request that uses N1+1 Block1 blocks. The server uses an empty 0.00 request that uses N1+1 Block1 blocks. The server uses an empty 0.00
ACK to announce the delayed response which is provided later with ACK to announce the delayed response, which is provided later with
2.04 messages containing N2+1 Block2 Options. The first 2.04 is a 2.04 messages containing N2+1 Block2 Options. The first 2.04 is a
confirmable message that is acknowledged by the client. Onwards, the Confirmable message that is acknowledged by the client. Onwards, the
client acknowledges all subsequent Block2 blocks. The notation of client acknowledges all subsequent Block2 blocks. The notation of
Figure 2 is explained in Appendix B.1. Figure 3 is explained in Appendix B.1.
POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256) {CSR (frag# 1)} --> POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256)
<-- (ACK) (1:0/1/256) (2.31 Continue) {CSR (frag# 1)} -->
POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR (frag# 2)} --> <-- (ACK) (1:0/1/256) (2.31 Continue)
<-- (ACK) (1:1/1/256) (2.31 Continue) POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256)
. {CSR (frag# 2)} -->
. <-- (ACK) (1:1/1/256) (2.31 Continue)
. .
POST [2001:db8::2:1]:61616/est/sen(CON)(1:N1/0/256){CSR (frag# N1+1)}--> .
<-- (0.00 empty ACK) .
| POST [2001:db8::2:1]:61616/est/sen(CON)(1:N1/0/256)
... Short delay before the certificate is ready ... {CSR (frag# N1+1)}-->
| <-- (0.00 empty ACK)
<-- (CON) (1:N1/0/256)(2:0/1/256)(2.04 Changed) {Cert resp (frag# 1)} |
(ACK) --> ... Short delay before the certificate is ready ...
POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/256) --> |
<-- (ACK) (2:1/1/256) (2.04 Changed) {Cert resp (frag# 2)} <-- (CON) (1:N1/0/256)(2:0/1/256)(2.04 Changed)
. {Cert resp (frag# 1)}
. (ACK) -->
. POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/256) -->
POST [2001:db8::2:1]:61616/est/sen (CON)(2:N2/0/256) --> <-- (ACK) (2:1/1/256) (2.04 Changed) {Cert resp (frag# 2)}
<-- (ACK) (2:N2/0/256) (2.04 Changed) {Cert resp (frag# N2+1)} .
.
.
POST [2001:db8::2:1]:61616/est/sen (CON)(2:N2/0/256) -->
<-- (ACK) (2:N2/0/256) (2.04 Changed) {Cert resp (frag# N2+1)}
Figure 2: EST-COAP enrollment with short wait Figure 3: EST-coaps Enrollment with Short Wait
If the server is very slow (for example, manual intervention is If the server is very slow (for example, manual intervention is
required which would take minutes), it SHOULD respond with an ACK required, which would take minutes), it SHOULD respond with an ACK
containing response code 5.03 (Service unavailable) and a Max-Age containing response code 5.03 (Service unavailable) and a Max-Age
Option to indicate the time the client SHOULD wait before sending Option to indicate the time the client SHOULD wait before sending
another request to obtain the content. After a delay of Max-Age, the another request to obtain the content. After a delay of Max-Age, the
client SHOULD resend the identical CSR to the server. As long as the client SHOULD resend the identical CSR to the server. As long as the
server continues to respond with response code 5.03 (Service server continues to respond with response code 5.03 (Service
Unavailable) with a Max-Age Option, the client will continue to delay Unavailable) with a Max-Age Option, the client will continue to delay
for Max-Age and then resend the enrollment request until the server for Max-Age and then resend the enrollment request until the server
responds with the certificate or the client abandons the request for responds with the certificate or the client abandons the request due
policy or other reasons. to policy or other reasons.
To demonstrate this scenario, Figure 3 shows a client sending an To demonstrate this scenario, Figure 4 shows a client sending an
enrollment request that uses N1+1 Block1 blocks to send the CSR to enrollment request that uses N1+1 Block1 blocks to send the CSR to
the server. The server needs N2+1 Block2 blocks to respond, but also the server. The server needs N2+1 Block2 blocks to respond but also
needs to take a long delay (minutes) to provide the response. needs to take a long delay (minutes) to provide the response.
Consequently, the server uses a 5.03 ACK response with a Max-Age Consequently, the server uses a 5.03 ACK response with a Max-Age
Option. The client waits for a period of Max-Age as many times as it Option. The client waits for a period of Max-Age as many times as it
receives the same 5.03 response and retransmits the enrollment receives the same 5.03 response and retransmits the enrollment
request until it receives a certificate in a fragmented 2.04 request until it receives a certificate in a fragmented 2.04
response. response.
POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256) {CSR (frag# 1)} --> POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256)
<-- (ACK) (1:0/1/256) (2.31 Continue) {CSR (frag# 1)} -->
POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR (frag# 2)} --> <-- (ACK) (1:0/1/256) (2.31 Continue)
<-- (ACK) (1:1/1/256) (2.31 Continue) POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256)
. {CSR (frag# 2)} -->
. <-- (ACK) (1:1/1/256) (2.31 Continue)
. .
POST [2001:db8::2:1]:61616/est/sen(CON)(1:N1/0/256){CSR (frag# N1+1)}--> .
<-- (ACK) (1:N1/0/256) (5.03 Service Unavailable) (Max-Age) .
| POST [2001:db8::2:1]:61616/est/sen(CON)(1:N1/0/256)
| {CSR (frag# N1+1)}-->
... Client tries again after Max-Age with identical payload ... <-- (ACK) (1:N1/0/256) (5.03 Service Unavailable) (Max-Age)
| |
| |
POST [2001:db8::2:1]:61616/est/sen(CON)(1:0/1/256){CSR (frag# 1)}--> ... Client tries again after Max-Age with identical payload ...
<-- (ACK) (1:0/1/256) (2.31 Continue) |
POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR (frag# 2)} --> |
<-- (ACK) (1:1/1/256) (2.31 Continue) POST [2001:db8::2:1]:61616/est/sen(CON)(1:0/1/256)
. {CSR (frag# 1)}-->
. <-- (ACK) (1:0/1/256) (2.31 Continue)
. POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256)
POST [2001:db8::2:1]:61616/est/sen(CON)(1:N1/0/256){CSR (frag# N1+1)}--> {CSR (frag# 2)} -->
| <-- (ACK) (1:1/1/256) (2.31 Continue)
... Immediate response when certificate is ready ... .
| .
<-- (ACK) (1:N1/0/256) (2:0/1/256) (2.04 Changed){Cert resp (frag# 1)} .
POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/256) --> POST [2001:db8::2:1]:61616/est/sen(CON)(1:N1/0/256)
<-- (ACK) (2:1/1/256) (2.04 Changed) {Cert resp (frag# 2)} {CSR (frag# N1+1)}-->
. |
. ... Immediate response when certificate is ready ...
. |
POST [2001:db8::2:1]:61616/est/sen (CON)(2:N2/0/256) --> <-- (ACK) (1:N1/0/256) (2:0/1/256) (2.04 Changed)
<-- (ACK) (2:N2/0/256) (2.04 Changed) {Cert resp (frag# N2+1)} {Cert resp (frag# 1)}
POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/256) -->
<-- (ACK) (2:1/1/256) (2.04 Changed) {Cert resp (frag# 2)}
.
.
.
POST [2001:db8::2:1]:61616/est/sen (CON)(2:N2/0/256) -->
<-- (ACK) (2:N2/0/256) (2.04 Changed) {Cert resp (frag# N2+1)}
Figure 3: EST-COAP enrollment with long wait Figure 4: EST-coaps Enrollment with Long Wait
5.8. Server-side Key Generation 4.8. Server-Side Key Generation
Private keys can be generated on the server to support scenarios Private keys can be generated on the server to support scenarios
where serer-side key generation is needed. Such scenarios include where server-side key generation is needed. Such scenarios include
those where it is considered more secure to generate the long-lived, those where it is considered more secure to generate the long-lived,
random private key that identifies the client at the server, or where random private key that identifies the client at the server, or where
the resources spent to generate a random private key at the client the resources spent to generate a random private key at the client
are considered scarce, or where the security policy requires that the are considered scarce, or where the security policy requires that the
certificate public and corresponding private keys are centrally certificate public and corresponding private keys are centrally
generated and controlled. As always, it is necessary to use proper generated and controlled. As always, it is necessary to use proper
random numbers in various protocols such as (D)TLS (Section 10.1). random numbers in various protocols such as (D)TLS (Section 9.1).
When requesting server-side key generation, the client asks for the When requesting server-side key generation, the client asks for the
server or proxy to generate the private key and the certificate, server or proxy to generate the private key and the certificate,
which are transferred back to the client in the server-side key which are transferred back to the client in the server-side key
generation response. In all respects, the server treats the CSR as generation response. In all respects, the server treats the CSR as
it would treat any enroll or re-enroll CSR; the only distinction here it would treat any enroll or re-enroll CSR; the only distinction here
is that the server MUST ignore the public key values and signature in is that the server MUST ignore the public key values and signature in
the CSR. These are included in the request only to allow re-use of the CSR. These are included in the request only to allow reuse of
existing codebases for generating and parsing such requests. existing codebases for generating and parsing such requests.
The client /skg request is for a certificate in a PKCS#7 container The client /skg request is for a certificate in a PKCS #7 container
and private key in two application/multipart-core elements. and private key in two application/multipart-core elements.
Respectively, an /skc request is for a single application/pkix-cert Respectively, an /skc request is for a single application/pkix-cert
certificate and a private key. The private key Content-Format certificate and a private key. The private key Content-Format
requested by the client is indicated in the PKCS#10 CSR request. If requested by the client is indicated in the PKCS #10 CSR request. If
the request contains SMIMECapabilities and DecryptKeyIdentifier or the request contains SMIMECapabilities and DecryptKeyIdentifier or
AsymmetricDecryptKeyIdentifier the client is expecting Content-Format AsymmetricDecryptKeyIdentifier, the client is expecting Content-
280 for the private key. Then this private key is encrypted Format 280 for the private key. Then, this private key is encrypted
symmetrically or asymmetrically as per [RFC7030]. The symmetric key symmetrically or asymmetrically per [RFC7030]. The symmetric key or
or the asymmetric keypair establishment method is out of scope of the asymmetric keypair establishment method is out of scope of this
this specification. A /skg or /skc request with a CSR without specification. An /skg or /skc request with a CSR without
SMIMECapabilities expects an application/multipart-core with an SMIMECapabilities expects an application/multipart-core with an
unencrypted PKCS#8 private key with Content-Format 284. unencrypted PKCS #8 private key with Content-Format 284.
The EST-coaps server-side key generation response is returned with The EST-coaps server-side key generation response is returned with
Content-Format application/multipart-core Content-Format application/multipart-core [RFC8710] containing a CBOR
[I-D.ietf-core-multipart-ct] containing a CBOR array with four items array with four items (Section 4.3). The two representations (each
(Section 5.3). The two representations (each consisting of two CBOR consisting of two CBOR array items) do not have to be in a particular
array items) do not have to be in a particular order since each order since each representation is preceded by its Content-Format ID.
representation is preceded by its Content-Format ID. Depending on Depending on the request, the private key can be in unprotected PKCS
the request, the private key can be in unprotected PKCS#8 [RFC5958] #8 format [RFC5958] (Content-Format 284) or protected inside of CMS
format (Content-Format 284) or protected inside of CMS SignedData SignedData (Content-Format 280). The SignedData, placed in the
(Content-Format 280). The SignedData, placed in the outermost outermost container, is signed by the party that generated the
container, is signed by the party that generated the private key, private key, which may be the EST server or the EST CA. SignedData
which may be the EST server or the EST CA. SignedData placed within placed within the Enveloped Data does not need additional signing as
the Enveloped Data does not need additional signing as explained in explained in Section 4.4.2 of [RFC7030]. In summary, the
Section 4.4.2 of [RFC7030]. In summary, the symmetrically encrypted symmetrically encrypted key is included in the encryptedKey attribute
key is included in the encryptedKey attribute in a KEKRecipientInfo in a KEKRecipientInfo structure. In the case where the asymmetric
structure. In the case where the asymmetric encryption key is encryption key is suitable for transport key operations, the
suitable for transport key operations the generated private key is generated private key is encrypted with a symmetric key. The
encrypted with a symmetric key. The symmetric key itself is symmetric key itself is encrypted by the client-defined (in the CSR)
encrypted by the client-defined (in the CSR) asymmetric public key asymmetric public key and is carried in an encryptedKey attribute in
and is carried in an encryptedKey attribute in a a KeyTransRecipientInfo structure. Finally, if the asymmetric
KeyTransRecipientInfo structure. Finally, if the asymmetric
encryption key is suitable for key agreement, the generated private encryption key is suitable for key agreement, the generated private
key is encrypted with a symmetric key. The symmetric key itself is key is encrypted with a symmetric key. The symmetric key itself is
encrypted by the client defined (in the CSR) asymmetric public key encrypted by the client defined (in the CSR) asymmetric public key
and is carried in an recipientEncryptedKeys attribute in a and is carried in a recipientEncryptedKeys attribute in a
KeyAgreeRecipientInfo. KeyAgreeRecipientInfo.
[RFC7030] recommends the use of additional encryption of the returned [RFC7030] recommends the use of additional encryption of the returned
private key. For the context of this specification, clients and private key. For the context of this specification, clients and
servers that choose to support server-side key generation MUST servers that choose to support server-side key generation MUST
support unprotected (PKCS#8) private keys (Content-Format 284). support unprotected (PKCS #8) private keys (Content-Format 284).
Symmetric or asymmetric encryption of the private key (CMS Symmetric or asymmetric encryption of the private key (CMS
EnvelopedData, Content-Format 280) SHOULD be supported for EnvelopedData, Content-Format 280) SHOULD be supported for
deployments where end-to-end encryption is needed between the client deployments where end-to-end encryption is needed between the client
and a server. Such cases could include architectures where an entity and a server. Such cases could include architectures where an entity
between the client and the CA terminates the DTLS connection between the client and the CA terminates the DTLS connection
(Registrar in Figure 4). Although [RFC7030] strongly recommends that (Registrar in Figure 5). Though [RFC7030] strongly recommends that
clients request the use of CMS encryption on top of the TLS channel's clients request the use of CMS encryption on top of the TLS channel's
protection, this document does not make such a recommendation; CMS protection, this document does not make such a recommendation; CMS
encryption can still be used when mandated by the use-case. encryption can still be used when mandated by the use case.
6. HTTPS-CoAPS Registrar 5. HTTPS-CoAPS Registrar
In real-world deployments, the EST server will not always reside In real-world deployments, the EST server will not always reside
within the CoAP boundary. The EST server can exist outside the within the CoAP boundary. The EST server can exist outside the
constrained network in which case it will support TLS/HTTP instead of constrained network, in which case it will support TLS/HTTP instead
CoAPS. In such environments EST-coaps is used by the client within of CoAPS. In such environments, EST-coaps is used by the client
the CoAP boundary and TLS is used to transport the EST messages within the CoAP boundary and TLS is used to transport the EST
outside the CoAP boundary. A Registrar at the edge is required to messages outside the CoAP boundary. A Registrar at the edge is
operate between the CoAP environment and the external HTTP network as required to operate between the CoAP environment and the external
shown in Figure 4. HTTP network as shown in Figure 5.
Constrained Network Constrained Network
.------. .----------------------------. .------. .----------------------------.
| CA | |.--------------------------.| | CA | |.--------------------------.|
'------' || || '------' || ||
| || || | || ||
.------. HTTP .-----------------. CoAPS .-----------. || .------. HTTP .------------------. CoAPS .-----------. ||
| EST |<------->|EST-coaps-to-HTTPS|<------->| EST Client| || | EST |<------->|EST-coaps-to-HTTPS|<------->| EST Client| ||
|Server|over TLS | Registrar | '-----------' || |Server|over TLS | Registrar | '-----------' ||
'------' '-----------------' || '------' '------------------' ||
|| || || ||
|'--------------------------'| |'--------------------------'|
'----------------------------' '----------------------------'
Figure 4: EST-coaps-to-HTTPS Registrar at the CoAP boundary. Figure 5: EST-coaps-to-HTTPS Registrar at the CoAP Boundary
The EST-coaps-to-HTTPS Registrar MUST terminate EST-coaps downstream The EST-coaps-to-HTTPS Registrar MUST terminate EST-coaps downstream
and initiate EST connections over TLS upstream. The Registrar MUST and initiate EST connections over TLS upstream. The Registrar MUST
authenticate and optionally authorize the client requests while it authenticate and optionally authorize the client requests while it
MUST be authenticated by the EST server or CA. The trust MUST be authenticated by the EST server or CA. The trust
relationship between the Registrar and the EST server SHOULD be pre- relationship between the Registrar and the EST server SHOULD be pre-
established for the Registrar to proxy these connections on behalf of established for the Registrar to proxy these connections on behalf of
various clients. various clients.
When enforcing Proof-of-Possession (PoP) linking, the DTLS tls-unique When enforcing Proof-of-Possession (POP) linking, the tls-unique or
value of the (D)TLS session is used to prove that the private key tls-exporter value of the session for DTLS 1.2 and DTLS 1.3,
corresponding to the public key is in the possession of the client respectively, is used to prove that the private key corresponding to
and was used to establish the connection as explained in Section 4. the public key is in the possession of the client and was used to
The PoP linking information is lost between the EST-coaps client and establish the connection as explained in Section 3. The POP linking
the EST server when a Registrar is present. The EST server becomes information is lost between the EST-coaps client and the EST server
aware of the presence of a Registrar from its TLS client certificate when a Registrar is present. The EST server becomes aware of the
that includes id-kp-cmcRA [RFC6402] extended key usage extension presence of a Registrar from its TLS client certificate that includes
(EKU). As explained in Section 3.7 of [RFC7030], the "EST server the id-kp-cmcRA extended key usage (EKU) extension [RFC6402]. As
SHOULD apply an authorization policy consistent with a Registrar explained in Section 3.7 of [RFC7030], the "EST server SHOULD apply
client. For example, it could be configured to accept PoP linking authorization policy consistent with an RA client ... the EST server
information that does not match the current TLS session because the could be configured to accept POP linking information that does not
authenticated EST client Registrar has verified this information when match the current TLS session because the authenticated EST client RA
acting as an EST server". has verified this information when acting as an EST server".
Table 1 contains the URI mappings between EST-coaps and EST that the Table 1 contains the URI mappings between EST-coaps and EST that the
Registrar MUST adhere to. Section 5.5 of this specification and Registrar MUST adhere to. Section 4.5 of this specification and
Section 7 of [RFC8075] define the mappings between EST-coaps and HTTP Section 7 of [RFC8075] define the mappings between EST-coaps and HTTP
response codes, that determine how the Registrar MUST translate CoAP response codes that determine how the Registrar MUST translate CoAP
response codes from/to HTTP status codes. The mapping from CoAP response codes from/to HTTP status codes. The mapping from CoAP
Content-Format to HTTP Content-Type is defined in Section 9.1. Content-Format to HTTP Content-Type is defined in Section 8.1.
Additionally, a conversion from CBOR major type 2 to Base64 encoding Additionally, a conversion from CBOR major type 2 to Base64 encoding
MUST take place at the Registrar. If CMS end-to-end encryption is MUST take place at the Registrar. If CMS end-to-end encryption is
employed for the private key, the encrypted CMS EnvelopedData blob employed for the private key, the encrypted CMS EnvelopedData blob
MUST be converted at the Registrar to binary CBOR type 2 downstream MUST be converted at the Registrar to binary CBOR type 2 downstream
to the client. This is a format conversion that does not require to the client. This is a format conversion that does not require
decryption of the CMS EnvelopedData. decryption of the CMS EnvelopedData.
A deviation from the mappings in Table 1 could take place if clients A deviation from the mappings in Table 1 could take place if clients
that leverage server-side key generation preferred for the enrolled that leverage server-side key generation preferred for the enrolled
keys to be generated by the Registrar in the case the CA does not keys to be generated by the Registrar in the case the CA does not
support server-side key generation. Such a Registrar is responsible support server-side key generation. Such a Registrar is responsible
for generating a new CSR signed by a new key which will be returned for generating a new CSR signed by a new key that will be returned to
to the client along with the certificate from the CA. In these the client along with the certificate from the CA. In these cases,
cases, the Registrar MUST use random number generation with proper the Registrar MUST use random number generation with proper entropy.
entropy.
Due to fragmentation of large messages into blocks, an EST-coaps-to- Due to fragmentation of large messages into blocks, an EST-coaps-to-
HTTP Registrar MUST reassemble the BLOCKs before translating the HTTP Registrar MUST reassemble the blocks before translating the
binary content to Base64, and consecutively relay the message binary content to Base64 and consecutively relay the message
upstream. upstream.
The EST-coaps-to-HTTP Registrar MUST support resource discovery The EST-coaps-to-HTTP Registrar MUST support resource discovery
according to the rules in Section 5.1. according to the rules in Section 4.1.
7. Parameters 6. Parameters
This section addresses transmission parameters described in sections This section addresses transmission parameters described in Sections
4.7 and 4.8 of [RFC7252]. EST does not impose any unique values on 4.7 and 4.8 of [RFC7252]. EST does not impose any unique values on
the CoAP parameters in [RFC7252], but the setting of the CoAP the CoAP parameters in [RFC7252], but the setting of the CoAP
parameter values may have consequence for the setting of the EST parameter values may have consequence for the setting of the EST
parameter values. parameter values.
Implementations should follow the default CoAP configuration Implementations should follow the default CoAP configuration
parameters [RFC7252]. However, depending on the implementation parameters [RFC7252]. However, depending on the implementation
scenario, retransmissions and timeouts can also occur on other scenario, retransmissions and timeouts can also occur on other
networking layers, governed by other configuration parameters. When networking layers, governed by other configuration parameters. When
a change in a server parameter has taken place, the parameter values a change in a server parameter has taken place, the parameter values
in the communicating endpoints MUST be adjusted as necessary. in the communicating endpoints MUST be adjusted as necessary.
Examples of how parameters could be adjusted include higher layer Examples of how parameters could be adjusted include higher-layer
congestion protocols, provisioning agents and configurations included congestion protocols, provisioning agents, and configurations
in firmware updates. included in firmware updates.
Some further comments about some specific parameters, mainly from Some further comments about some specific parameters, mainly from
Table 2 in [RFC7252]: Table 2 in [RFC7252], include the following:
o NSTART: A parameter that controls the number of simultaneous NSTART: A parameter that controls the number of simultaneous
outstanding interactions that a client maintains to a given outstanding interactions that a client maintains to a given
server. An EST-coaps client is expected to control at most one server. An EST-coaps client is expected to control at most one
interaction with a given server, which is the default NSTART value interaction with a given server, which is the default NSTART value
defined in [RFC7252]. defined in [RFC7252].
o DEFAULT_LEISURE: This setting is only relevant in multicast DEFAULT_LEISURE: A setting that is only relevant in multicast
scenarios, outside the scope of EST-coaps. scenarios and is outside the scope of EST-coaps.
o PROBING_RATE: A parameter which specifies the rate of re-sending PROBING_RATE: A parameter that specifies the rate of resending Non-
non-confirmable messages. In the rare situations that non- confirmable messages. In the rare situations that Non-confirmable
confirmable messages are used, the default PROBING_RATE value messages are used, the default PROBING_RATE value defined in
defined in [RFC7252] applies. [RFC7252] applies.
Finally, the Table 3 parameters in [RFC7252] are mainly derived from Finally, the Table 3 parameters in [RFC7252] are mainly derived from
Table 2. Directly changing parameters on one table would affect Table 2. Directly changing parameters on one table would affect
parameters on the other. parameters on the other.
8. Deployment limitations 7. Deployment Limitations
Although EST-coaps paves the way for the utilization of EST by Although EST-coaps paves the way for the utilization of EST by
constrained devices in constrained networks, some classes of devices constrained devices in constrained networks, some classes of devices
[RFC7228] will not have enough resources to handle the payloads that [RFC7228] will not have enough resources to handle the payloads that
come with EST-coaps. The specification of EST-coaps is intended to come with EST-coaps. The specification of EST-coaps is intended to
ensure that EST works for networks of constrained devices that choose ensure that EST works for networks of constrained devices that choose
to limit their communications stack to DTLS/CoAP. It is up to the to limit their communications stack to DTLS/CoAP. It is up to the
network designer to decide which devices execute the EST protocol and network designer to decide which devices execute the EST protocol and
which do not. which do not.
9. IANA Considerations 8. IANA Considerations
9.1. Content-Format Registry 8.1. Content-Formats Registry
Additions to the sub-registry "CoAP Content-Formats", within the IANA has registered the following Content-Formats given in Table 5 in
"CoRE Parameters" registry [COREparams] are specified in Table 5. the "CoAP Content-Formats" subregistry within the "CoRE Parameters"
These have been registered provisionally in the IETF Review or IESG registry [CORE-PARAMS]. These have been registered in the IETF
Approval range (256-9999). Review or IESG Approval range (256-9999).
+------------------------------+-------+----------------------------+ +=================================+=====+====================+
| HTTP Content-Type | ID | Reference | | Media Type | ID | Reference |
+------------------------------+-------+----------------------------+ +=================================+=====+====================+
| application/pkcs7-mime; | 280 | [RFC7030] [I-D.ietf-lamps- | | application/pkcs7-mime; smime- | 280 | [RFC7030] |
| smime-type=server-generated- | | rfc5751-bis] [ThisRFC] | | type=server-generated-key | | [RFC8551] RFC 9148 |
| key | | | +---------------------------------+-----+--------------------+
| application/pkcs7-mime; | 281 | [I-D.ietf-lamps-rfc5751-bi | | application/pkcs7-mime; smime- | 281 | [RFC8551] RFC 9148 |
| smime-type=certs-only | | s] [ThisRFC] | | type=certs-only | | |
| application/pkcs8 | 284 | [RFC5958] [I-D.ietf-lamps- | +---------------------------------+-----+--------------------+
| | | rfc5751-bis] [ThisRFC] | | application/pkcs8 | 284 | [RFC5958] |
| application/csrattrs | 285 | [RFC7030] | | | | [RFC8551] RFC 9148 |
| application/pkcs10 | 286 | [RFC5967] [I-D.ietf-lamps- | +---------------------------------+-----+--------------------+
| | | rfc5751-bis] [ThisRFC] | | application/csrattrs | 285 | [RFC7030] RFC 9148 |
| application/pkix-cert | TBD28 | [RFC2585] [ThisRFC] | +---------------------------------+-----+--------------------+
| | 7 | | | application/pkcs10 | 286 | [RFC5967] |
+------------------------------+-------+----------------------------+ | | | [RFC8551] RFC 9148 |
+---------------------------------+-----+--------------------+
| application/pkix-cert | 287 | [RFC2585] RFC 9148 |
+---------------------------------+-----+--------------------+
Table 5: New CoAP Content-Formats Table 5: New CoAP Content-Formats
It is suggested that 287 is allocated to TBD287. 8.2. Resource Type Registry
9.2. Resource Type registry IANA has registered the following Resource Type (rt=) Link Target
Attributes given in Table 6 in the "Resource Type (rt=) Link Target
Attribute Values" subregistry under the "Constrained RESTful
Environments (CoRE) Parameters" registry.
This memo registers new Resource Type (rt=) Link Target Attributes in +==============+===================================+===========+
the "Resource Type (rt=) Link Target Attribute Values" subregistry | Value | Description | Reference |
under the "Constrained RESTful Environments (CoRE) Parameters" +==============+===================================+===========+
registry. | ace.est.crts | This resource depicts the support | RFC 9148 |
| | of EST GET cacerts. | |
+--------------+-----------------------------------+-----------+
| ace.est.sen | This resource depicts the support | RFC 9148 |
| | of EST simple enroll. | |
+--------------+-----------------------------------+-----------+
| ace.est.sren | This resource depicts the support | RFC 9148 |
| | of EST simple reenroll. | |
+--------------+-----------------------------------+-----------+
| ace.est.att | This resource depicts the support | RFC 9148 |
| | of EST GET CSR attributes. | |
+--------------+-----------------------------------+-----------+
| ace.est.skg | This resource depicts the support | RFC 9148 |
| | of EST server-side key generation | |
| | with the returned certificate in | |
| | a PKCS #7 container. | |
+--------------+-----------------------------------+-----------+
| ace.est.skc | This resource depicts the support | RFC 9148 |
| | of EST server-side key generation | |
| | with the returned certificate in | |
| | application/pkix-cert format. | |
+--------------+-----------------------------------+-----------+
o rt="ace.est.crts". This resource depicts the support of EST get Table 6: New Resource Type (rt=) Link Target Attributes
cacerts.
o rt="ace.est.sen". This resource depicts the support of EST simple 8.3. Well-Known URIs Registry
enroll.
o rt="ace.est.sren". This resource depicts the support of EST IANA has added an additional reference to the est URI in the "Well-
simple reenroll. Known URIs" registry:
o rt="ace.est.att". This resource depicts the support of EST get URI Suffix: est
CSR attributes.
o rt="ace.est.skg". This resource depicts the support of EST Change Controller: IETF
server-side key generation with the returned certificate in a
PKCS#7 container.
o rt="ace.est.skc". This resource depicts the support of EST References: [RFC7030] RFC 9148
server-side key generation with the returned certificate in
application/pkix-cert format.
9.3. Well-Known URIs Registry Status: permanent
A new additional reference is requested for the est URI in the Well- Related Information:
Known URIs registry:
+------+--------+---------+---------+----------+---------+----------+ Date Registered: 2013-08-16
| URI | Change | Referen | Status | Related | Date Re | Date |
| Suff | Contro | ces | | Informat | gistere | Modified |
| ix | ller | | | ion | d | |
+------+--------+---------+---------+----------+---------+----------+
| est | IETF | [RFC703 | permane | | 2013-08 | [THIS |
| | | 0] | nt | | -16 | RFC's pu |
| | | [THIS | | | | blicatio |
| | | RFC] | | | | n date] |
+------+--------+---------+---------+----------+---------+----------+
10. Security Considerations Date Modified: 2020-04-29
10.1. EST server considerations 9. Security Considerations
The security considerations of Section 6 of [RFC7030] are only 9.1. EST Server Considerations
The security considerations in Section 6 of [RFC7030] are only
partially valid for the purposes of this document. As HTTP Basic partially valid for the purposes of this document. As HTTP Basic
Authentication is not supported, the considerations expressed for Authentication is not supported, the considerations expressed for
using passwords do not apply. The other portions of the security using passwords do not apply. The other portions of the security
considerations of [RFC7030] continue to apply. considerations in [RFC7030] continue to apply.
Modern security protocols require random numbers to be available Modern security protocols require random numbers to be available
during the protocol run, for example for nonces and ephemeral (EC) during the protocol run, for example, for nonces and ephemeral (EC)
Diffie-Hellman key generation. This capability to generate random Diffie-Hellman key generation. This capability to generate random
numbers is also needed when the constrained device generates the numbers is also needed when the constrained device generates the
private key (that corresponds to the public key enrolled in the CSR). private key (that corresponds to the public key enrolled in the CSR).
When server-side key generation is used, the constrained device When server-side key generation is used, the constrained device
depends on the server to generate the private key randomly, but it depends on the server to generate the private key randomly, but it
still needs locally generated random numbers for use in security still needs locally generated random numbers for use in security
protocols, as explained in Section 12 of [RFC7925]. Additionally, protocols, as explained in Section 12 of [RFC7925]. Additionally,
the transport of keys generated at the server is inherently risky. the transport of keys generated at the server is inherently risky.
For those deploying server-side key generation, analysis SHOULD be For those deploying server-side key generation, analysis SHOULD be
done to establish whether server-side key generation increases or done to establish whether server-side key generation increases or
decreases the probability of digital identity theft. decreases the probability of digital identity theft.
It is important to note that, as pointed out in [PsQs], sources It is important to note that, as pointed out in [PsQs], sources
contributing to the randomness pool used to generate random numbers contributing to the randomness pool used to generate random numbers
on laptops or desktop PCs, such as mouse movement, timing of on laptops or desktop PCs, such as mouse movement, timing of
keystrokes, or air turbulence on the movement of hard drive heads, keystrokes, or air turbulence on the movement of hard drive heads,
are not available on many constrained devices. Other sources have to are not available on many constrained devices. Other sources have to
be used or dedicated hardware has to be added. Selecting hardware be used or dedicated hardware has to be added. Selecting hardware
for an IoT device that is capable of producing high-quality random for an IoT device that is capable of producing high-quality random
numbers is therefore important [RSAfact]. numbers is therefore important [RSA-FACT].
As discussed in Section 6 of [RFC7030], it is "RECOMMENDED that the As discussed in Section 6 of [RFC7030], it is
Implicit Trust Anchor database used for EST server authentication is
carefully managed to reduce the chance of a third-party CA with poor
certification practices jeopardizing authentication. Disabling the
Implicit Trust Anchor database after successfuly receiving the
Distribution of CA certificates response (Section 4.1.3) limits any
risk to the first TLS exchange". Alternatively, in a case where a
/sen request immediately follows a /crts, a client MAY choose to keep
the connection authenticated by the Implicit TA open for efficiency
reasons (Section 4). A client that interleaves EST-coaps /crts
request with other requests in the same DTLS connection SHOULD
revalidate the server certificate chain against the updated Explicit
TA from the /crts response before proceeding with the subsequent
requests. If the server certificate chain does not authenticate
against the database, the client SHOULD close the connection without
completing the rest of the requests. The updated Explicit TA MUST
continue to be used in new DTLS connections.
In cases where the IDevID used to authenticate the client is expired | RECOMMENDED that the Implicit Trust Anchor database used for EST
the server MAY still authenticate the client because IDevIDs are | server authentication be carefully managed to reduce the chance of
expected to live as long as the device itself (Section 4). In such | a third-party CA with poor certification practices from being
occasions, checking the certificate revocation status or authorizing | trusted. Disabling the Implicit Trust Anchor database after
the client using another method is important for the server to raise | successfully receiving the Distribution of CA certificates
its confidence that the client can be trusted. | response ([RFC7030], Section 6) limits any vulnerability to the
| first TLS exchange.
Alternatively, in a case where a /sen request immediately follows a
/crts, a client MAY choose to keep the connection authenticated by
the Implicit TA open for efficiency reasons (Section 3). A client
that interleaves EST-coaps /crts request with other requests in the
same DTLS connection SHOULD revalidate the server certificate chain
against the updated Explicit TA from the /crts response before
proceeding with the subsequent requests. If the server certificate
chain does not authenticate against the database, the client SHOULD
close the connection without completing the rest of the requests.
The updated Explicit TA MUST continue to be used in new DTLS
connections.
In cases where the Initial Device Identifier (IDevID) used to
authenticate the client is expired, the server MAY still authenticate
the client because IDevIDs are expected to live as long as the device
itself (Section 3). In such occasions, checking the certificate
revocation status or authorizing the client using another method is
important for the server to raise its confidence that the client can
be trusted.
In accordance with [RFC7030], TLS cipher suites that include In accordance with [RFC7030], TLS cipher suites that include
"_EXPORT_" and "_DES_" in their names MUST NOT be used. More "_EXPORT_" and "_DES_" in their names MUST NOT be used. More
recommendations for secure use of TLS and DTLS are included in recommendations for secure use of TLS and DTLS are included in
[BCP195]. [BCP195].
As described in CMC, Section 6.7 of [RFC5272], "For keys that can be As described in Certificate Management over CMS (CMC), Section 6.7 of
used as signature keys, signing the certification request with the [RFC5272], "For keys that can be used as signature keys, signing the
private key serves as a PoP on that key pair". The inclusion of tls- certification request with the private key serves as a POP on that
unique in the certificate request links the proof-of-possession to key pair". In (D)TLS 1.2, the inclusion of tls-unique in the
the TLS proof-of-identity. This implies but does not prove that only certificate request links the proof-of-possession to the (D)TLS
the authenticated client currently has access to the private key. proof-of-identity. This implies but does not prove that only the
authenticated client currently has access to the private key.
What's more, CMC PoP linking uses tls-unique as it is defined in What's more, CMC POP linking uses tls-unique as it is defined in
[RFC5929]. The 3SHAKE attack [tripleshake] poses a risk by allowing [RFC5929]. The 3SHAKE attack [TRIPLESHAKE] poses a risk by allowing
a man-in-the-middle to leverage session resumption and renegotiation an on-path active attacker to leverage session resumption and
to inject himself between a client and server even when channel renegotiation to inject itself between a client and server even when
binding is in use. Implementers should use the Extended Master channel binding is in use. Implementers should use the Extended
Secret Extension in DTLS [RFC7627] to prevent such attacks. In the Master Secret Extension in DTLS [RFC7627] to prevent such attacks.
context of this specification, an attacker could invalidate the In the context of this specification, an attacker could invalidate
purpose of the PoP linking ChallengePassword in the client request by the purpose of the POP linking challengePassword in the client
resuming an EST-coaps connection. Even though the practical risk of request by resuming an EST-coaps connection. Even though the
such an attack to EST-coaps is not devastating, we would rather use a practical risk of such an attack to EST-coaps is not devastating, we
more secure channel binding mechanism. Such a mechanism could would rather use a more secure channel-binding mechanism. In this
include an updated tls-unique value generation like the tls-unique- specification, we still depend on the tls-unique mechanism defined in
prf defined in [I-D.josefsson-sasl-tls-cb] by using a TLS exporter [RFC5929] for DTLS 1.2 because a 3SHAKE attack does not expose
[RFC5705] in TLS 1.2 or TLS 1.3's updated exporter (Section 7.5 of messages exchanged with EST-coaps. But for DTLS 1.3,
[RFC8446]) value in place of the tls-unique value in the CSR. Such [TLS13-CHANNEL-BINDINGS] is used instead to derive a 32-byte tls-
mechanism has not been standardized yet. Adopting a channel binding exporter binding in place of the tls-unique value in the CSR. That
value generated from an exporter would break backwards compatibility would alleviate the risks from the 3SHAKE attack [TRIPLESHAKE].
for an RA that proxies through to a classic EST server. Thus, in
this specification we still depend on the tls-unique mechanism
defined in [RFC5929], especially since a 3SHAKE attack does not
expose messages exchanged with EST-coaps.
Interpreters of ASN.1 structures should be aware of the use of Interpreters of ASN.1 structures should be aware of the use of
invalid ASN.1 length fields and should take appropriate measures to invalid ASN.1 length fields and should take appropriate measures to
guard against buffer overflows, stack overruns in particular, and guard against buffer overflows, stack overruns in particular, and
malicious content in general. malicious content in general.
10.2. HTTPS-CoAPS Registrar considerations 9.2. HTTPS-CoAPS Registrar Considerations
The Registrar proposed in Section 6 must be deployed with care, and The Registrar proposed in Section 5 must be deployed with care and
only when direct client-server connections are not possible. When only when direct client-server connections are not possible. When
PoP linking is used the Registrar terminating the DTLS connection POP linking is used, the Registrar terminating the DTLS connection
establishes a new TLS connection with the upstream CA. Thus, it is establishes a new TLS connection with the upstream CA. Thus, it is
impossible for PoP linking to be enforced end-to-end for the EST impossible for POP linking to be enforced end to end for the EST
transaction. The EST server could be configured to accept PoP transaction. The EST server could be configured to accept POP
linking information that does not match the current TLS session linking information that does not match the current TLS session
because the authenticated EST Registrar is assumed to have verified because the authenticated EST Registrar is assumed to have verified
PoP linking downstream to the client. POP linking downstream to the client.
The introduction of an EST-coaps-to-HTTP Registrar assumes the client The introduction of an EST-coaps-to-HTTP Registrar assumes the client
can authenticate the Registrar using its implicit or explicit TA can authenticate the Registrar using its implicit or explicit TA
database. It also assumes the Registrar has a trust relationship database. It also assumes the Registrar has a trust relationship
with the upstream EST server in order to act on behalf of the with the upstream EST server in order to act on behalf of the
clients. When a client uses the Implicit TA database for certificate clients. When a client uses the Implicit TA database for certificate
validation, it SHOULD confirm if the server is acting as an RA by the validation, it SHOULD confirm if the server is acting as an RA by the
presence of the id-kp-cmcRA EKU [RFC6402] in the server certificate. presence of the id-kp-cmcRA EKU [RFC6402] in the server certificate.
In a server-side key generation case, if no end-to-end encryption is In a server-side key generation case, if no end-to-end encryption is
used, the Registrar may be able see the private key as it acts as a used, the Registrar may be able see the private key as it acts as a
man-in-the-middle. Thus, the client puts its trust on the Registrar man in the middle. Thus, the client puts its trust on the Registrar
not exposing the private key. not exposing the private key.
Clients that leverage server-side key generation without end-to-end Clients that leverage server-side key generation without end-to-end
encryption of the private key (Section 5.8) have no knowledge if the encryption of the private key (Section 4.8) have no knowledge as to
Registrar will be generating the private key and enrolling the whether the Registrar will be generating the private key and
certificates with the CA or if the CA will be responsible for enrolling the certificates with the CA or if the CA will be
generating the key. In such cases, the existence of a Registrar responsible for generating the key. In such cases, the existence of
requires the client to put its trust on the registrar when it is a Registrar requires the client to put its trust on the Registrar
generating the private key. when it is generating the private key.
11. Contributors
Martin Furuhed contributed to the EST-coaps specification by
providing feedback based on the Nexus EST over CoAPS server
implementation that started in 2015. Sandeep Kumar kick-started this
specification and was instrumental in drawing attention to the
importance of the subject.
12. Acknowledgements
The authors are very grateful to Klaus Hartke for his detailed
explanations on the use of Block with DTLS and his support for the
Content-Format specification. The authors would like to thank Esko
Dijk and Michael Verschoor for the valuable discussions that helped
in shaping the solution. They would also like to thank Peter
Panburana for his feedback on technical details of the solution.
Constructive comments were received from Benjamin Kaduk, Eliot Lear,
Jim Schaad, Hannes Tschofenig, Julien Vermillard, John Manuel, Oliver
Pfaff, Pete Beal and Carsten Bormann.
Interop tests were done by Oliver Pfaff, Thomas Werner, Oskar
Camezind, Bjorn Elmers and Joel Hoglund.
Robert Moskowitz provided code to create the examples.
13. References
13.1. Normative References
[I-D.ietf-core-multipart-ct]
Fossati, T., Hartke, K., and C. Bormann, "Multipart
Content-Format for CoAP", draft-ietf-core-multipart-ct-04
(work in progress), August 2019.
[I-D.ietf-lamps-rfc5751-bis] 10. References
Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Message Specification", draft-ietf-lamps-rfc5751-bis-12
(work in progress), September 2018.
[I-D.ietf-tls-dtls13] 10.1. Normative References
Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", draft-ietf-tls-dtls13-34 (work in progress),
November 2019.
[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>.
[RFC2585] Housley, R. and P. Hoffman, "Internet X.509 Public Key [RFC2585] Housley, R. and P. Hoffman, "Internet X.509 Public Key
Infrastructure Operational Protocols: FTP and HTTP", Infrastructure Operational Protocols: FTP and HTTP",
RFC 2585, DOI 10.17487/RFC2585, May 1999, RFC 2585, DOI 10.17487/RFC2585, May 1999,
<https://www.rfc-editor.org/info/rfc2585>. <https://www.rfc-editor.org/info/rfc2585>.
skipping to change at page 30, line 41 skipping to change at line 1227
[RFC8422] Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic [RFC8422] Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic
Curve Cryptography (ECC) Cipher Suites for Transport Layer Curve Cryptography (ECC) Cipher Suites for Transport Layer
Security (TLS) Versions 1.2 and Earlier", RFC 8422, Security (TLS) Versions 1.2 and Earlier", RFC 8422,
DOI 10.17487/RFC8422, August 2018, DOI 10.17487/RFC8422, August 2018,
<https://www.rfc-editor.org/info/rfc8422>. <https://www.rfc-editor.org/info/rfc8422>.
[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>.
13.2. Informative References [RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Message Specification", RFC 8551, DOI 10.17487/RFC8551,
April 2019, <https://www.rfc-editor.org/info/rfc8551>.
[RFC8710] Fossati, T., Hartke, K., and C. Bormann, "Multipart
Content-Format for the Constrained Application Protocol
(CoAP)", RFC 8710, DOI 10.17487/RFC8710, February 2020,
<https://www.rfc-editor.org/info/rfc8710>.
[RFC9147] Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
<https://www.rfc-editor.org/info/rfc9147>.
10.2. Informative References
[BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre, [BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer "Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, May 2015, (DTLS)", BCP 195, RFC 7525, May 2015.
<https://www.rfc-editor.org/info/bcp195>.
[COREparams]
"Constrained RESTful Environments (CoRE) Parameters",
<https://www.iana.org/assignments/core-parameters/core-
parameters.xhtml>.
[I-D.ietf-tls-dtls-connection-id] <https://www.rfc-editor.org/info/bcp195>
Rescorla, E., Tschofenig, H., and T. Fossati, "Connection
Identifiers for DTLS 1.2", draft-ietf-tls-dtls-connection-
id-07 (work in progress), October 2019.
[I-D.josefsson-sasl-tls-cb] [CORE-PARAMS]
Josefsson, S., "Channel Bindings for TLS based on the IANA, "Constrained RESTful Environments (CoRE)
PRF", draft-josefsson-sasl-tls-cb-03 (work in progress), Parameters",
March 2015. <https://www.iana.org/assignments/core-parameters/>.
[I-D.moskowitz-ecdsa-pki] [IEEE802.15.4]
Moskowitz, R., Birkholz, H., Xia, L., and M. Richardson, IEEE, "IEEE 802.15.4-2020 - IEEE Standard for Low-Rate
"Guide for building an ECC pki", draft-moskowitz-ecdsa- Wireless Networks", May 2020.
pki-07 (work in progress), August 2019.
[ieee802.15.4] [IEEE802.1AR]
"IEEE Standard 802.15.4-2006", 2006. IEEE, "IEEE Standard for Local and metropolitan area
networks - Secure Device Identity", December 2009.
[ieee802.1ar] [PKI-GUIDE]
"IEEE 802.1AR Secure Device Identifier", December 2009. Moskowitz, R., Birkholz, H., Xia, L., and M. Richardson,
"Guide for building an ECC pki", Work in Progress,
Internet-Draft, draft-moskowitz-ecdsa-pki-10, 31 January
2021, <https://datatracker.ietf.org/doc/html/draft-
moskowitz-ecdsa-pki-10>.
[PsQs] "Mining Your Ps and Qs: Detection of Widespread Weak Keys [PsQs] Heninger, N., Durumeric, Z., Wustrow, E., and J. Alex
in Network Devices", USENIX Security Symposium 2012 ISBN Halderman, "Mining Your Ps and Qs: Detection of Widespread
978-931971-95-9, August 2012. Weak Keys in Network Devices", USENIX Security Symposium
2012, ISBN 978-931971-95-9, August 2012.
[RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 [RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
over Low-Power Wireless Personal Area Networks (6LoWPANs): over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals", Overview, Assumptions, Problem Statement, and Goals",
RFC 4919, DOI 10.17487/RFC4919, August 2007, RFC 4919, DOI 10.17487/RFC4919, August 2007,
<https://www.rfc-editor.org/info/rfc4919>. <https://www.rfc-editor.org/info/rfc4919>.
[RFC5272] Schaad, J. and M. Myers, "Certificate Management over CMS [RFC5272] Schaad, J. and M. Myers, "Certificate Management over CMS
(CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008, (CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008,
<https://www.rfc-editor.org/info/rfc5272>. <https://www.rfc-editor.org/info/rfc5272>.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
March 2010, <https://www.rfc-editor.org/info/rfc5705>.
[RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings [RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings
for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010, for TLS", RFC 5929, DOI 10.17487/RFC5929, July 2010,
<https://www.rfc-editor.org/info/rfc5929>. <https://www.rfc-editor.org/info/rfc5929>.
[RFC6402] Schaad, J., "Certificate Management over CMS (CMC) [RFC6402] Schaad, J., "Certificate Management over CMS (CMC)
Updates", RFC 6402, DOI 10.17487/RFC6402, November 2011, Updates", RFC 6402, DOI 10.17487/RFC6402, November 2011,
<https://www.rfc-editor.org/info/rfc6402>. <https://www.rfc-editor.org/info/rfc6402>.
[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,
skipping to change at page 32, line 34 skipping to change at line 1323
[RFC7627] Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A., [RFC7627] Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A.,
Langley, A., and M. Ray, "Transport Layer Security (TLS) Langley, A., and M. Ray, "Transport Layer Security (TLS)
Session Hash and Extended Master Secret Extension", Session Hash and Extended Master Secret Extension",
RFC 7627, DOI 10.17487/RFC7627, September 2015, RFC 7627, DOI 10.17487/RFC7627, September 2015,
<https://www.rfc-editor.org/info/rfc7627>. <https://www.rfc-editor.org/info/rfc7627>.
[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>.
[RSAfact] "Factoring RSA keys from certified smart cards: [RFC9146] Rescorla, E., Ed., Tschofenig, H., Ed., Fossati, T., and
Coppersmith in the wild", Advances in Cryptology A. Kraus, "Connection Identifier for DTLS 1.2", RFC 9146,
- ASIACRYPT 2013, August 2013. DOI 10.17487/RFC9146, March 2022,
<https://www.rfc-editor.org/info/rfc9146>.
[tripleshake] [RSA-FACT] Bernstein, D., Chang, Y., Cheng, C., Chou, L., Heninger,
"Triple Handshakes and Cookie Cutters: Breaking and Fixing N., Lange, T., and N. Someren, "Factoring RSA keys from
Authentication over TLS", IEEE Security and Privacy ISBN certified smart cards: Coppersmith in the wild", Advances
978-1-4799-4686-0, May 2014. in Cryptology - ASIACRYPT 2013, August 2013.
Appendix A. EST messages to EST-coaps [TLS13-CHANNEL-BINDINGS]
Whited, S., "Channel Bindings for TLS 1.3", Work in
Progress, Internet-Draft, draft-ietf-kitten-tls-channel-
bindings-for-tls13-15, 4 March 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-kitten-
tls-channel-bindings-for-tls13-15>.
[TRIPLESHAKE]
Bhargavan, B., Delignat-Lavaud, A., Fournet, C., Pironti,
A., and P. Strub, "Triple Handshakes and Cookie Cutters:
Breaking and Fixing Authentication over TLS",
ISBN 978-1-4799-4686-0, DOI 10.1109/SP.2014.14, May 2014,
<https://doi.org/10.1109/SP.2014.14>.
Appendix A. EST Messages to EST-coaps
This section shows similar examples to the ones presented in This section shows similar examples to the ones presented in
Appendix A of [RFC7030]. The payloads in the examples are the hex Appendix A of [RFC7030]. The payloads in the examples are the hex-
encoded binary, generated with 'xxd -p', of the PKI certificates encoded binary, generated with 'xxd -p', of the PKI certificates
created following [I-D.moskowitz-ecdsa-pki]. Hex is used for created following [PKI-GUIDE]. Hex is used for visualization
visualization purposes because a binary representation cannot be purposes because a binary representation cannot be rendered well in
rendered well in text. The hexadecimal representations would not be text. The hexadecimal representations would not be transported in
transported in hex, but in binary. The payloads are shown hex, but in binary. The payloads are shown unencrypted. In
unencrypted. In practice the message content would be transferred practice, the message content would be transferred over an encrypted
over an encrypted DTLS channel. DTLS channel.
The certificate responses included in the examples contain Content- The certificate responses included in the examples contain Content-
Format 281 (application/pkcs7). If the client had requested Content- Format 281 (application/pkcs7). If the client had requested Content-
Format TBD287 (application/pkix-cert) by querying /est/skc, the Format 287 (application/pkix-cert), the server would respond with a
server would respond with a single DER binary certificate in the single DER binary certificate. That certificate would be in a
multipart-core container. multipart-core container specifically in the case of a response to a
/est/skc query.
These examples assume a short resource path of "/est". Even though These examples assume a short resource path of "/est". Even though
omitted from the examples for brevity, before making the EST-coaps omitted from the examples for brevity, before making the EST-coaps
requests, a client would learn about the server supported EST-coaps requests, a client would learn about the server supported EST-coaps
resources with a GET request for /.well-known/core?rt=ace.est* as resources with a GET request for /.well-known/core?rt=ace.est* as
explained in Section 5.1. explained in Section 4.1.
The corresponding CoAP headers are only shown in Appendix A.1. The corresponding CoAP headers are only shown in Appendix A.1.
Creating CoAP headers is assumed to be generally understood. Creating CoAP headers is assumed to be generally understood.
The message content breakdown is presented in Appendix C. The message content is presented in plain text in Appendix C.
A.1. cacerts A.1. cacerts
In EST-coaps, a cacerts message can be: In EST-coaps, a cacerts message can be the following:
GET example.com:9085/est/crts GET example.com:9085/est/crts
(Accept: 281) (Accept: 281)
The corresponding CoAP header fields are shown below. The use of The corresponding CoAP header fields are shown below. The use of
block and DTLS are worked out in Appendix B. block and DTLS are shown in Appendix B.
Ver = 1 Ver = 1
T = 0 (CON) T = 0 (CON)
Code = 0x01 (0.01 is GET) Code = 0x01 (0.01 is GET)
Token = 0x9a (client generated) Token = 0x9a (client generated)
Options Options
Option (Uri-Host) Option (Uri-Host)
Option Delta = 0x3 (option# 3) Option Delta = 0x3 (option# 3)
Option Length = 0xB Option Length = 0xB
Option Value = "example.com" Option Value = "example.com"
skipping to change at page 34, line 34 skipping to change at line 1416
Option Length = 0x4 Option Length = 0x4
Option Value = "crts" Option Value = "crts"
Option (Accept) Option (Accept)
Option Delta = 0x6 (option# 11+6=17) Option Delta = 0x6 (option# 11+6=17)
Option Length = 0x2 Option Length = 0x2
Option Value = 281 Option Value = 281
Payload = [Empty] Payload = [Empty]
As specified in Section 5.10.1 of [RFC7252], the Uri-Host and Uri- As specified in Section 5.10.1 of [RFC7252], the Uri-Host and Uri-
Port Options can be omitted if they coincide with the transport Port Options can be omitted if they coincide with the transport
protocol destination address and port respectively. protocol destination address and port, respectively.
A 2.05 Content response with a cert in EST-coaps will then be A 2.05 Content response with a cert in EST-coaps will then be the
following:
2.05 Content (Content-Format: 281) 2.05 Content (Content-Format: 281)
{payload with certificate in binary format} {payload with certificate in binary format}
with CoAP fields With the following CoAP fields:
Ver = 1 Ver = 1
T = 2 (ACK) T = 2 (ACK)
Code = 0x45 (2.05 Content) Code = 0x45 (2.05 Content)
Token = 0x9a (copied from request by server) Token = 0x9a (copied from request by server)
Options Options
Option (Content-Format) Option (Content-Format)
Option Delta = 0xC (option# 12) Option Delta = 0xC (option# 12)
Option Length = 0x2 Option Length = 0x2
Option Value = 281 Option Value = 281
skipping to change at page 35, line 42 skipping to change at line 1464
595fcc8e37f8e4354497011be90e56794bd91ad951ab45a3818430818130 595fcc8e37f8e4354497011be90e56794bd91ad951ab45a3818430818130
1d0603551d0e041604141df1208944d77b5f1d9dcb51ee244a523f3ef5de 1d0603551d0e041604141df1208944d77b5f1d9dcb51ee244a523f3ef5de
301f0603551d230418301680141df1208944d77b5f1d9dcb51ee244a523f 301f0603551d230418301680141df1208944d77b5f1d9dcb51ee244a523f
3ef5de300f0603551d130101ff040530030101ff300e0603551d0f0101ff 3ef5de300f0603551d130101ff040530030101ff300e0603551d0f0101ff
040403020106301e0603551d110417301581136365727469667940657861 040403020106301e0603551d110417301581136365727469667940657861
6d706c652e636f6d300a06082a8648ce3d040302034800304502202b891d 6d706c652e636f6d300a06082a8648ce3d040302034800304502202b891d
d411d07a6d6f621947635ba4c43165296b3f633726f02e51ecf464bd4002 d411d07a6d6f621947635ba4c43165296b3f633726f02e51ecf464bd4002
2100b4be8a80d08675f041fbc719acf3b39dedc85dc92b3035868cb2daa8 2100b4be8a80d08675f041fbc719acf3b39dedc85dc92b3035868cb2daa8
f05db196a1003100 f05db196a1003100
The breakdown of the payload is shown in Appendix C.1. The payload is shown in plain text in Appendix C.1.
A.2. enroll / reenroll A.2. enroll / reenroll
During the (re-)enroll exchange the EST-coaps client uses a CSR During the (re-)enroll exchange, the EST-coaps client uses a CSR
(Content-Format 286) request in the POST request payload. The Accept (Content-Format 286) request in the POST request payload. The Accept
option tells the server that the client is expecting Content-Format Option tells the server that the client is expecting Content-Format
281 (PKCS#7) in the response. As shown in Appendix C.2, the CSR 281 (PKCS #7) in the response. As shown in Appendix C.2, the CSR
contains a ChallengePassword which is used for PoP linking contains a challengePassword, which is used for POP linking
(Section 4). (Section 3).
POST [2001:db8::2:321]:61616/est/sen POST [2001:db8::2:321]:61616/est/sen
(Token: 0x45) (Token: 0x45)
(Accept: 281) (Accept: 281)
(Content-Format: 286) (Content-Format: 286)
[ The hexadecimal representation below would NOT be transported [ The hexadecimal representation below would NOT be transported
in hex, but in binary. Hex is used because a binary representation in hex, but in binary. Hex is used because a binary representation
cannot be rendered well in text. ] cannot be rendered well in text. ]
skipping to change at page 37, line 35 skipping to change at line 1532
ff958d75419d81a6a245dffae790be95cf75f602f9152618f816a2b23b56 ff958d75419d81a6a245dffae790be95cf75f602f9152618f816a2b23b56
38e59fd9a3818a30818730090603551d1304023000301d0603551d0e0416 38e59fd9a3818a30818730090603551d1304023000301d0603551d0e0416
041496600d8716bf7fd0e752d0ac760777ad665d02a0301f0603551d2304 041496600d8716bf7fd0e752d0ac760777ad665d02a0301f0603551d2304
183016801468d16551f951bfc82a431d0d9f08bc2d205b1160300e060355 183016801468d16551f951bfc82a431d0d9f08bc2d205b1160300e060355
1d0f0101ff0404030205a0302a0603551d1104233021a01f06082b060105 1d0f0101ff0404030205a0302a0603551d1104233021a01f06082b060105
05070804a013301106092b06010401b43b0a01040401020304300a06082a 05070804a013301106092b06010401b43b0a01040401020304300a06082a
8648ce3d0403020349003046022100c0d81996d2507d693f3c48eaa5ee94 8648ce3d0403020349003046022100c0d81996d2507d693f3c48eaa5ee94
91bda6db214099d98117c63b361374cd86022100a774989f4c321a5cf25d 91bda6db214099d98117c63b361374cd86022100a774989f4c321a5cf25d
832a4d336a08ad67df20f1506421188a0ade6d349236a1003100 832a4d336a08ad67df20f1506421188a0ade6d349236a1003100
The breakdown of the request and response is shown in Appendix C.2. The request and response is shown in plain text in Appendix C.2.
A.3. serverkeygen A.3. serverkeygen
In a serverkeygen exchange the CoAP POST request looks like In a serverkeygen exchange, the CoAP POST request looks like the
following:
POST 192.0.2.1:8085/est/skg POST 192.0.2.1:8085/est/skg
(Token: 0xa5) (Token: 0xa5)
(Accept: 62) (Accept: 62)
(Content-Format: 286) (Content-Format: 286)
[ The hexadecimal representation below would NOT be transported [ The hexadecimal representation below would NOT be transported
in hex, but in binary. Hex is used because a binary representation in hex, but in binary. Hex is used because a binary representation
cannot be rendered well in text. ] cannot be rendered well in text. ]
3081d03078020100301631143012060355040a0c0b736b67206578616d70 3081d03078020100301631143012060355040a0c0b736b67206578616d70
6c653059301306072a8648ce3d020106082a8648ce3d03010703420004c8 6c653059301306072a8648ce3d020106082a8648ce3d03010703420004c8
b421f11c25e47e3ac57123bf2d9fdc494f028bc351cc80c03f150bf50cff b421f11c25e47e3ac57123bf2d9fdc494f028bc351cc80c03f150bf50cff
958d75419d81a6a245dffae790be95cf75f602f9152618f816a2b23b5638 958d75419d81a6a245dffae790be95cf75f602f9152618f816a2b23b5638
e59fd9a000300a06082a8648ce3d040302034800304502207c553981b1fe e59fd9a000300a06082a8648ce3d040302034800304502207c553981b1fe
349249d8a3f50a0346336b7dfaa099cf74e1ec7a37a0a760485902210084 349249d8a3f50a0346336b7dfaa099cf74e1ec7a37a0a760485902210084
79295398774b2ff8e7e82abb0c17eaef344a5088fa69fd63ee611850c34b 79295398774b2ff8e7e82abb0c17eaef344a5088fa69fd63ee611850c34b
0a 0a
The response would follow [I-D.ietf-core-multipart-ct] and could look The response would follow [RFC8710] and could look like the
like following:
2.04 Changed 2.04 Changed
(Token: 0xa5) (Token: 0xa5)
(Content-Format: 62) (Content-Format: 62)
[ The hexadecimal representations below would NOT be transported [ The hexadecimal representations below would NOT be transported
in hex, but in binary. Hex is used because a binary representation in hex, but in binary. Hex is used because a binary representation
cannot be rendered well in text. ] cannot be rendered well in text. ]
84 # array(4) 84 # array(4)
19 011C # unsigned(284) 19 011C # unsigned(284)
skipping to change at page 39, line 40 skipping to change at line 1596
2618f816a2b23b5638e59fd9a37b307930090603551d1304023000302c06 2618f816a2b23b5638e59fd9a37b307930090603551d1304023000302c06
096086480186f842010d041f161d4f70656e53534c2047656e6572617465 096086480186f842010d041f161d4f70656e53534c2047656e6572617465
64204365727469666963617465301d0603551d0e0416041496600d8716bf 64204365727469666963617465301d0603551d0e0416041496600d8716bf
7fd0e752d0ac760777ad665d02a0301f0603551d2304183016801496600d 7fd0e752d0ac760777ad665d02a0301f0603551d2304183016801496600d
8716bf7fd0e752d0ac760777ad665d02a0300a06082a8648ce3d04030203 8716bf7fd0e752d0ac760777ad665d02a0300a06082a8648ce3d04030203
48003045022100e95bfa25a08976652246f2d96143da39fce0dc4c9b26b9 48003045022100e95bfa25a08976652246f2d96143da39fce0dc4c9b26b9
cce1f24164cc2b12b602201351fd8eea65764e3459d324e4345ff5b2a915 cce1f24164cc2b12b602201351fd8eea65764e3459d324e4345ff5b2a915
38c04976111796b3698bf6379ca1003100 38c04976111796b3698bf6379ca1003100
The private key in the response above is without CMS EnvelopedData The private key in the response above is without CMS EnvelopedData
and has no additional encryption beyond DTLS (Section 5.8). and has no additional encryption beyond DTLS (Section 4.8).
The breakdown of the request and response is shown in Appendix C.3 The request and response is shown in plain text in Appendix C.3.
A.4. csrattrs A.4. csrattrs
Below is a csrattrs exchange The following is a csrattrs exchange:
REQ: REQ:
GET example.com:61616/est/att GET example.com:61616/est/att
RES: RES:
2.05 Content 2.05 Content
(Content-Format: 285) (Content-Format: 285)
[ The hexadecimal representation below would NOT be transported [ The hexadecimal representation below would NOT be transported
in hex, but in binary. Hex is used because a binary representation in hex, but in binary. Hex is used because a binary representation
cannot be rendered well in text. ] cannot be rendered well in text. ]
307c06072b06010101011630220603883701311b131950617273652053455 307c06072b06010101011630220603883701311b131950617273652053455
420617320322e3939392e31206461746106092a864886f70d010907302c06 420617320322e3939392e31206461746106092a864886f70d010907302c06
0388370231250603883703060388370413195061727365205345542061732 0388370231250603883703060388370413195061727365205345542061732
0322e3939392e32206461746106092b240303020801010b06096086480165 0322e3939392e32206461746106092b240303020801010b06096086480165
03040202 03040202
A 2.05 Content response should contain attributes which are relevant A 2.05 Content response should contain attributes that are relevant
for the authenticated client. This example is copied from for the authenticated client. This example is copied from
Section A.2 in [RFC7030], where the base64 representation is replaced Appendix A.2 of [RFC7030], where the base64 representation is
with a hexadecimal representation of the equivalent binary format. replaced with a hexadecimal representation of the equivalent binary
The EST-coaps server returns attributes that the client can ignore if format. The EST-coaps server returns attributes that the client can
they are unknown to him. ignore if they are unknown to the client.
Appendix B. EST-coaps Block message examples Appendix B. EST-coaps Block Message Examples
Two examples are presented in this section: Two examples are presented in this section:
1. a cacerts exchange shows the use of Block2 and the block headers 1. A cacerts exchange shows the use of Block2 and the block headers.
2. an enroll exchange shows the Block1 and Block2 size negotiation 2. An enroll exchange shows the Block1 and Block2 size negotiation
for request and response payloads. for request and response payloads.
The payloads are shown unencrypted. In practice the message contents The payloads are shown unencrypted. In practice, the message
would be binary formatted and transferred over an encrypted DTLS contents would be binary formatted and transferred over an encrypted
tunnel. The corresponding CoAP headers are only shown in DTLS tunnel. The corresponding CoAP headers are only shown in
Appendix B.1. Creating CoAP headers is assumed to be generally Appendix B.1. Creating CoAP headers is assumed to be generally
known. known.
B.1. cacerts B.1. cacerts
This section provides a detailed example of the messages using DTLS This section provides a detailed example of the messages using DTLS
and BLOCK option Block2. The example block length is taken as 64 and CoAP Option Block2. The example block length is taken as 64,
which gives an SZX value of 2. which gives an SZX value of 2.
The following is an example of a cacerts exchange over DTLS. The The following is an example of a cacerts exchange over DTLS. The
content length of the cacerts response in appendix A.1 of [RFC7030] content length of the cacerts response in Appendix A.1 of [RFC7030]
contains 639 bytes in binary in this example. The CoAP message adds contains 639 bytes in binary in this example. The CoAP message adds
around 10 bytes in this exmple, the DTLS record around 29 bytes. To around 10 bytes in this example, and the DTLS record around 29 bytes.
avoid IP fragmentation, the CoAP Block Option is used and an MTU of To avoid IP fragmentation, the CoAP Block Option is used and an MTU
127 is assumed to stay within one IEEE 802.15.4 packet. To stay of 127 is assumed to stay within one IEEE 802.15.4 packet. To stay
below the MTU of 127, the payload is split in 9 packets with a below the MTU of 127, the payload is split in 9 packets with a
payload of 64 bytes each, followed by a last tenth packet of 63 payload of 64 bytes each, followed by a last tenth packet of 63
bytes. The client sends an IPv6 packet containing a UDP datagram bytes. The client sends an IPv6 packet containing a UDP datagram
with DTLS record protection that encapsulates a CoAP request 10 times with DTLS record protection that encapsulates a CoAP request 10 times
(one fragment of the request per block). The server returns an IPv6 (one fragment of the request per block). The server returns an IPv6
packet containing a UDP datagram with the DTLS record that packet containing a UDP datagram with the DTLS record that
encapsulates the CoAP response. The CoAP request-response exchange encapsulates the CoAP response. The CoAP request-response exchange
with block option is shown below. Block Option is shown in a with block option is shown below. Block Option is shown in a
decomposed way (block-option:NUM/M/size) indicating the kind of Block decomposed way (block-option:NUM/M/size) indicating the kind of Block
Option (2 in this case) followed by a colon, and then the block Option (2 in this case) followed by a colon, and then the block
number (NUM), the more bit (M = 0 in Block2 response means it is last number (NUM), the more bit (M = 0 in Block2 response means it is last
block), and block size with exponent (2**(SZX+4)) separated by block), and block size with exponent (2^(SZX+4)) separated by
slashes. The Length 64 is used with SZX=2. The CoAP Request is sent slashes. The Length 64 is used with SZX=2. The CoAP Request is sent
confirmable (CON) and the Content-Format of the response, even though Confirmable (CON), and the Content-Format of the response, even
not shown, is 281 (application/pkcs7-mime; smime-type=certs-only). though not shown, is 281 (application/pkcs7-mime; smime-type=certs-
The transfer of the 10 blocks with partially filled block NUM=9 is only). The transfer of the 10 blocks with partially filled block
shown below NUM=9 is shown below.
GET example.com:9085/est/crts (2:0/0/64) --> GET example.com:9085/est/crts (2:0/0/64) -->
<-- (2:0/1/64) 2.05 Content <-- (2:0/1/64) 2.05 Content
GET example.com:9085/est/crts (2:1/0/64) --> GET example.com:9085/est/crts (2:1/0/64) -->
<-- (2:1/1/64) 2.05 Content <-- (2:1/1/64) 2.05 Content
| |
| |
| |
GET example.com:9085/est/crts (2:9/0/64) --> GET example.com:9085/est/crts (2:9/0/64) -->
<-- (2:9/0/64) 2.05 Content <-- (2:9/0/64) 2.05 Content
The header of the GET request looks like The header of the GET request looks like the following:
Ver = 1 Ver = 1
T = 0 (CON) T = 0 (CON)
Code = 0x01 (0.1 GET) Code = 0x01 (0.1 GET)
Token = 0x9a (client generated) Token = 0x9a (client generated)
Options Options
Option (Uri-Host) Option (Uri-Host)
Option Delta = 0x3 (option# 3) Option Delta = 0x3 (option# 3)
Option Length = 0xB Option Length = 0xB
Option Value = "example.com" Option Value = "example.com"
Option (Uri-Port) Option (Uri-Port)
skipping to change at page 42, line 32 skipping to change at line 1713
Option Delta = 0x0 (option# 11+0=11) Option Delta = 0x0 (option# 11+0=11)
Option Length = 0x4 Option Length = 0x4
Option Value = "crts" Option Value = "crts"
Option (Accept) Option (Accept)
Option Delta = 0x6 (option# 11+6=17) Option Delta = 0x6 (option# 11+6=17)
Option Length = 0x2 Option Length = 0x2
Option Value = 281 Option Value = 281
Payload = [Empty] Payload = [Empty]
The Uri-Host and Uri-Port Options can be omitted if they coincide The Uri-Host and Uri-Port Options can be omitted if they coincide
with the transport protocol destination address and port with the transport protocol destination address and port,
respectively. Explicit Uri-Host and Uri-Port Options are typically respectively. Explicit Uri-Host and Uri-Port Options are typically
used when an endpoint hosts multiple virtual servers and uses the used when an endpoint hosts multiple virtual servers and uses the
Options to route the requests accordingly. Options to route the requests accordingly.
For further detailing the CoAP headers, the first two and the last To provide further details on the CoAP headers, the first two and the
blocks are written out below. The header of the first Block2 last blocks are written out below. The header of the first Block2
response looks like response looks like the following:
Ver = 1 Ver = 1
T = 2 (ACK) T = 2 (ACK)
Code = 0x45 (2.05 Content) Code = 0x45 (2.05 Content)
Token = 0x9a (copied from request by server) Token = 0x9a (copied from request by server)
Options Options
Option Option
Option Delta = 0xC (option# 12 Content-Format) Option Delta = 0xC (option# 12 Content-Format)
Option Length = 0x2 Option Length = 0x2
Option Value = 281 Option Value = 281
Option Option
skipping to change at page 43, line 27 skipping to change at line 1745
[ The hexadecimal representation below would NOT be transported [ The hexadecimal representation below would NOT be transported
in hex, but in binary. Hex is used because a binary representation in hex, but in binary. Hex is used because a binary representation
cannot be rendered well in text. ] cannot be rendered well in text. ]
Payload = Payload =
3082027b06092a864886f70d010702a082026c308202680201013100300b 3082027b06092a864886f70d010702a082026c308202680201013100300b
06092a864886f70d010701a082024e3082024a308201f0a0030201020209 06092a864886f70d010701a082024e3082024a308201f0a0030201020209
009189bc 009189bc
The second Block2: The header of the second Block2 response looks like the following:
Ver = 1 Ver = 1
T = 2 (means ACK) T = 2 (means ACK)
Code = 0x45 (2.05 Content) Code = 0x45 (2.05 Content)
Token = 0x9a (copied from request by server) Token = 0x9a (copied from request by server)
Options Options
Option Option
Option Delta = 0xC (option# 12 Content-Format) Option Delta = 0xC (option# 12 Content-Format)
Option Length = 0x2 Option Length = 0x2
Option Value = 281 Option Value = 281
skipping to change at page 44, line 4 skipping to change at line 1769
Option Value = 0x1A (block#=1, M=1, SZX=2) Option Value = 0x1A (block#=1, M=1, SZX=2)
[ The hexadecimal representation below would NOT be transported [ The hexadecimal representation below would NOT be transported
in hex, but in binary. Hex is used because a binary representation in hex, but in binary. Hex is used because a binary representation
cannot be rendered well in text. ] cannot be rendered well in text. ]
Payload = Payload =
df9c99244b300a06082a8648ce3d0403023067310b300906035504061302 df9c99244b300a06082a8648ce3d0403023067310b300906035504061302
5553310b300906035504080c024341310b300906035504070c024c413114 5553310b300906035504080c024341310b300906035504070c024c413114
30120603 30120603
The 10th and final Block2:
The header of the tenth and final Block2 response looks like the
following:
Ver = 1 Ver = 1
T = 2 (means ACK) T = 2 (means ACK)
Code = 0x45 (2.05 Content) Code = 0x45 (2.05 Content)
Token = 0x9a (copied from request by server) Token = 0x9a (copied from request by server)
Options Options
Option Option
Option Delta = 0xC (option# 12 Content-Format) Option Delta = 0xC (option# 12 Content-Format)
Option Length = 0x2 Option Length = 0x2
Option Value = 281 Option Value = 281
skipping to change at page 44, line 33 skipping to change at line 1800
Payload = Payload =
2ec0b4af52d46f3b7ecc9687ddf267bcec368f7b7f1353272f022047a28a 2ec0b4af52d46f3b7ecc9687ddf267bcec368f7b7f1353272f022047a28a
e5c7306163b3c3834bab3c103f743070594c089aaa0ac870cd13b902caa1 e5c7306163b3c3834bab3c103f743070594c089aaa0ac870cd13b902caa1
003100 003100
B.2. enroll / reenroll B.2. enroll / reenroll
In this example, the requested Block2 size of 256 bytes, required by In this example, the requested Block2 size of 256 bytes, required by
the client, is transferred to the server in the very first request the client, is transferred to the server in the very first request
message. The block size 256=(2**(SZX+4)) which gives SZX=4. The message. The block size of 256 is equal to (2^(SZX+4)), which gives
notation for block numbering is the same as in Appendix B.1. The SZX=4. The notation for block numbering is the same as in
header fields and the payload are omitted for brevity. Appendix B.1. The header fields and the payload are omitted for
brevity.
POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256) {CSR (frag# 1)} --> POST [2001:db8::2:1]:61616/est/sen (CON)(1:0/1/256)
{CSR (frag# 1)} -->
<-- (ACK) (1:0/1/256) (2.31 Continue) <-- (ACK) (1:0/1/256) (2.31 Continue)
POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256) {CSR (frag# 2)} --> POST [2001:db8::2:1]:61616/est/sen (CON)(1:1/1/256)
<-- (ACK) (1:1/1/256) (2.31 Continue) {CSR (frag# 2)} -->
. <-- (ACK) (1:1/1/256) (2.31 Continue)
. .
. .
POST [2001:db8::2:1]:61616/est/sen (CON)(1:N1/0/256){CSR(frag# N1+1)}--> .
| POST [2001:db8::2:1]:61616/est/sen (CON)(1:N1/0/256)
...........Immediate response ......... {CSR(frag# N1+1)}-->
| |
<-- (ACK) (1:N1/0/256)(2:0/1/256)(2.04 Changed){Cert resp (frag# 1)} ...........Immediate response .........
POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/256) --> |
<-- (ACK) (2:1/1/256)(2.04 Changed) {Cert resp (frag# 2)} <-- (ACK) (1:N1/0/256)(2:0/1/256)(2.04 Changed)
. {Cert resp (frag# 1)}
. POST [2001:db8::2:1]:61616/est/sen (CON)(2:1/0/256) -->
. <-- (ACK) (2:1/1/256)(2.04 Changed)
POST [2001:db8::2:321]:61616/est/sen (CON)(2:N2/0/256) --> {Cert resp (frag# 2)}
<-- (ACK) (2:N2/0/256) (2.04 Changed) {Cert resp (frag# N2+1)} .
.
.
POST [2001:db8::2:321]:61616/est/sen (CON)(2:N2/0/256) -->
<-- (ACK) (2:N2/0/256) (2.04 Changed)
{Cert resp (frag# N2+1)}
Figure 5: EST-COAP enrollment with multiple blocks Figure 6: EST-coaps Enrollment with Multiple Blocks
N1+1 blocks have been transferred from client to the server and N2+1 N1+1 blocks have been transferred from client to server, and N2+1
blocks have been transferred from server to client. blocks have been transferred from server to client.
Appendix C. Message content breakdown Appendix C. Message Content Breakdown
This appendix presents the breakdown of the hexadecimal dumps of the This appendix presents the hexadecimal dumps of the binary payloads
binary payloads shown in Appendix A. in plain text shown in Appendix A.
C.1. cacerts C.1. cacerts
The breakdown of cacerts response containing one root CA certificate The cacerts response containing one root CA certificate is presented
is in plain text in the following:
Certificate: Certificate:
Data: Data:
Version: 3 (0x2) Version: 3 (0x2)
Serial Number: 831953162763987486 (0xb8bb0fe604f6a1e) Serial Number: 831953162763987486 (0xb8bb0fe604f6a1e)
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
Issuer: C=US, ST=CA, L=LA, O=Example Inc, Issuer: C=US, ST=CA, L=LA, O=Example Inc,
OU=certification, CN=Root CA OU=certification, CN=Root CA
Validity Validity
Not Before: Jan 31 11:27:03 2019 GMT Not Before: Jan 31 11:27:03 2019 GMT
Not After : Jan 26 11:27:03 2039 GMT Not After : Jan 26 11:27:03 2039 GMT
skipping to change at page 46, line 48 skipping to change at line 1891
X509v3 Subject Alternative Name: X509v3 Subject Alternative Name:
email:certify@example.com email:certify@example.com
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
30:45:02:20:2b:89:1d:d4:11:d0:7a:6d:6f:62:19:47:63:5b: 30:45:02:20:2b:89:1d:d4:11:d0:7a:6d:6f:62:19:47:63:5b:
a4:c4:31:65:29:6b:3f:63:37:26:f0:2e:51:ec:f4:64:bd:40: a4:c4:31:65:29:6b:3f:63:37:26:f0:2e:51:ec:f4:64:bd:40:
02:21:00:b4:be:8a:80:d0:86:75:f0:41:fb:c7:19:ac:f3:b3: 02:21:00:b4:be:8a:80:d0:86:75:f0:41:fb:c7:19:ac:f3:b3:
9d:ed:c8:5d:c9:2b:30:35:86:8c:b2:da:a8:f0:5d:b1:96 9d:ed:c8:5d:c9:2b:30:35:86:8c:b2:da:a8:f0:5d:b1:96
C.2. enroll / reenroll C.2. enroll / reenroll
The breakdown of the enrollment request is The enrollment request is presented in plain text in the following:
Certificate Request: Certificate Request:
Data: Data:
Version: 0 (0x0) Version: 0 (0x0)
Subject: C=US, ST=CA, L=LA, O=example Inc, Subject: C=US, ST=CA, L=LA, O=example Inc,
OU=IoT/serialNumber=Wt1234 OU=IoT/serialNumber=Wt1234
Subject Public Key Info: Subject Public Key Info:
Public Key Algorithm: id-ecPublicKey Public Key Algorithm: id-ecPublicKey
Public-Key: (256 bit) Public-Key: (256 bit)
pub: pub:
04:c8:b4:21:f1:1c:25:e4:7e:3a:c5:71:23:bf:2d: 04:c8:b4:21:f1:1c:25:e4:7e:3a:c5:71:23:bf:2d:
9f:dc:49:4f:02:8b:c3:51:cc:80:c0:3f:15:0b:f5: 9f:dc:49:4f:02:8b:c3:51:cc:80:c0:3f:15:0b:f5:
0c:ff:95:8d:75:41:9d:81:a6:a2:45:df:fa:e7:90: 0c:ff:95:8d:75:41:9d:81:a6:a2:45:df:fa:e7:90:
be:95:cf:75:f6:02:f9:15:26:18:f8:16:a2:b2:3b: be:95:cf:75:f6:02:f9:15:26:18:f8:16:a2:b2:3b:
56:38:e5:9f:d9 56:38:e5:9f:d9
ASN1 OID: prime256v1 ASN1 OID: prime256v1
NIST CURVE: P-256 NIST CURVE: P-256
Attributes: Attributes:
challengePassword: <256-bit PoP linking value> challengePassword: <256-bit POP linking value>
Requested Extensions: Requested Extensions:
X509v3 Subject Alternative Name: X509v3 Subject Alternative Name:
othername:<unsupported> othername:<unsupported>
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
30:45:02:21:00:92:56:3a:54:64:63:bd:9e:cf:f1:70:d0:fd: 30:45:02:21:00:92:56:3a:54:64:63:bd:9e:cf:f1:70:d0:fd:
1f:2e:f0:d3:d0:12:16:0e:5e:e9:0c:ff:ed:ab:ec:9b:9a:38: 1f:2e:f0:d3:d0:12:16:0e:5e:e9:0c:ff:ed:ab:ec:9b:9a:38:
92:02:20:17:9f:10:a3:43:61:09:05:1a:ba:d1:75:90:a0:9b: 92:02:20:17:9f:10:a3:43:61:09:05:1a:ba:d1:75:90:a0:9b:
c8:7c:4d:ce:54:53:a6:fc:11:35:a1:e8:4e:ed:75:43:77 c8:7c:4d:ce:54:53:a6:fc:11:35:a1:e8:4e:ed:75:43:77
The CSR contains a ChallengePassword which is used for PoP linking The CSR contains a challengePassword, which is used for POP linking
(Section 4). The CSR also contains an id-on-hardwareModuleName (Section 3). The CSR also contains an id-on-hardwareModuleName
hardware identifier to customize the returned certificate to the hardware identifier to customize the returned certificate to the
requesting device (See [RFC7299] and [I-D.moskowitz-ecdsa-pki]). requesting device (See [RFC7299] and [PKI-GUIDE]).
The issued certificate presented in plain text in the following:
The breakdown of the issued certificate is
Certificate: Certificate:
Data: Data:
Version: 3 (0x2) Version: 3 (0x2)
Serial Number: 9112578475118446130 (0x7e7661d7b54e4632) Serial Number: 9112578475118446130 (0x7e7661d7b54e4632)
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
Issuer: C=US, ST=CA, O=Example Inc, Issuer: C=US, ST=CA, O=Example Inc,
OU=certification, CN=802.1AR CA OU=certification, CN=802.1AR CA
Validity Validity
Not Before: Jan 31 11:29:16 2019 GMT Not Before: Jan 31 11:29:16 2019 GMT
Not After : Dec 31 23:59:59 9999 GMT Not After : Dec 31 23:59:59 9999 GMT
skipping to change at page 48, line 48 skipping to change at line 1971
X509v3 Subject Alternative Name: X509v3 Subject Alternative Name:
othername:<unsupported> othername:<unsupported>
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
30:46:02:21:00:c0:d8:19:96:d2:50:7d:69:3f:3c:48:ea:a5: 30:46:02:21:00:c0:d8:19:96:d2:50:7d:69:3f:3c:48:ea:a5:
ee:94:91:bd:a6:db:21:40:99:d9:81:17:c6:3b:36:13:74:cd: ee:94:91:bd:a6:db:21:40:99:d9:81:17:c6:3b:36:13:74:cd:
86:02:21:00:a7:74:98:9f:4c:32:1a:5c:f2:5d:83:2a:4d:33: 86:02:21:00:a7:74:98:9f:4c:32:1a:5c:f2:5d:83:2a:4d:33:
6a:08:ad:67:df:20:f1:50:64:21:18:8a:0a:de:6d:34:92:36 6a:08:ad:67:df:20:f1:50:64:21:18:8a:0a:de:6d:34:92:36
C.3. serverkeygen C.3. serverkeygen
The following is the breakdown of the server-side key generation The following is the server-side key generation request presented in
request. plain text:
Certificate Request: Certificate Request:
Data: Data:
Version: 0 (0x0) Version: 0 (0x0)
Subject: O=skg example Subject: O=skg example
Subject Public Key Info: Subject Public Key Info:
Public Key Algorithm: id-ecPublicKey Public Key Algorithm: id-ecPublicKey
Public-Key: (256 bit) Public-Key: (256 bit)
pub: pub:
04:c8:b4:21:f1:1c:25:e4:7e:3a:c5:71:23:bf:2d: 04:c8:b4:21:f1:1c:25:e4:7e:3a:c5:71:23:bf:2d:
skipping to change at page 49, line 28 skipping to change at line 1997
ASN1 OID: prime256v1 ASN1 OID: prime256v1
NIST CURVE: P-256 NIST CURVE: P-256
Attributes: Attributes:
a0:00 a0:00
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
30:45:02:20:7c:55:39:81:b1:fe:34:92:49:d8:a3:f5:0a:03: 30:45:02:20:7c:55:39:81:b1:fe:34:92:49:d8:a3:f5:0a:03:
46:33:6b:7d:fa:a0:99:cf:74:e1:ec:7a:37:a0:a7:60:48:59: 46:33:6b:7d:fa:a0:99:cf:74:e1:ec:7a:37:a0:a7:60:48:59:
02:21:00:84:79:29:53:98:77:4b:2f:f8:e7:e8:2a:bb:0c:17: 02:21:00:84:79:29:53:98:77:4b:2f:f8:e7:e8:2a:bb:0c:17:
ea:ef:34:4a:50:88:fa:69:fd:63:ee:61:18:50:c3:4b:0a ea:ef:34:4a:50:88:fa:69:fd:63:ee:61:18:50:c3:4b:0a
Following is the breakdown of the private key content of the server- The following is the private key content of the server-side key
side key generation response. generation response presented in plain text:
Private-Key: (256 bit) Private-Key: (256 bit)
priv: priv:
61:33:6a:86:ac:6e:7a:f4:a9:6f:63:28:30:ad:4e: 61:33:6a:86:ac:6e:7a:f4:a9:6f:63:28:30:ad:4e:
6a:a0:83:76:79:20:60:94:d7:67:9a:01:ca:8c:6f: 6a:a0:83:76:79:20:60:94:d7:67:9a:01:ca:8c:6f:
0c:37 0c:37
pub: pub:
04:c8:b4:21:f1:1c:25:e4:7e:3a:c5:71:23:bf:2d: 04:c8:b4:21:f1:1c:25:e4:7e:3a:c5:71:23:bf:2d:
9f:dc:49:4f:02:8b:c3:51:cc:80:c0:3f:15:0b:f5: 9f:dc:49:4f:02:8b:c3:51:cc:80:c0:3f:15:0b:f5:
0c:ff:95:8d:75:41:9d:81:a6:a2:45:df:fa:e7:90: 0c:ff:95:8d:75:41:9d:81:a6:a2:45:df:fa:e7:90:
be:95:cf:75:f6:02:f9:15:26:18:f8:16:a2:b2:3b: be:95:cf:75:f6:02:f9:15:26:18:f8:16:a2:b2:3b:
56:38:e5:9f:d9 56:38:e5:9f:d9
ASN1 OID: prime256v1 ASN1 OID: prime256v1
NIST CURVE: P-256 NIST CURVE: P-256
The following is the breakdown of the certificate in the server-side The following is the certificate in the server-side key generation
key generation response payload. response payload presented in plain text:
Certificate: Certificate:
Data: Data:
Version: 3 (0x2) Version: 3 (0x2)
Serial Number: Serial Number:
b3:31:3e:8f:3f:c9:53:8e b3:31:3e:8f:3f:c9:53:8e
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
Issuer: O=skg example Issuer: O=skg example
Validity Validity
Not Before: Sep 4 07:44:03 2019 GMT Not Before: Sep 4 07:44:03 2019 GMT
skipping to change at page 50, line 44 skipping to change at line 2056
X509v3 Authority Key Identifier: X509v3 Authority Key Identifier:
keyid: keyid:
96:60:0D:87:16:BF:7F:D0:E7:52:D0:AC:76:07:77:AD:66:5D:02:A0 96:60:0D:87:16:BF:7F:D0:E7:52:D0:AC:76:07:77:AD:66:5D:02:A0
Signature Algorithm: ecdsa-with-SHA256 Signature Algorithm: ecdsa-with-SHA256
30:45:02:21:00:e9:5b:fa:25:a0:89:76:65:22:46:f2:d9:61: 30:45:02:21:00:e9:5b:fa:25:a0:89:76:65:22:46:f2:d9:61:
43:da:39:fc:e0:dc:4c:9b:26:b9:cc:e1:f2:41:64:cc:2b:12: 43:da:39:fc:e0:dc:4c:9b:26:b9:cc:e1:f2:41:64:cc:2b:12:
b6:02:20:13:51:fd:8e:ea:65:76:4e:34:59:d3:24:e4:34:5f: b6:02:20:13:51:fd:8e:ea:65:76:4e:34:59:d3:24:e4:34:5f:
f5:b2:a9:15:38:c0:49:76:11:17:96:b3:69:8b:f6:37:9c f5:b2:a9:15:38:c0:49:76:11:17:96:b3:69:8b:f6:37:9c
Acknowledgements
The authors are very grateful to Klaus Hartke for his detailed
explanations on the use of Block with DTLS and his support for the
Content-Format specification. The authors would like to thank Esko
Dijk and Michael Verschoor for the valuable discussions that helped
in shaping the solution. They would also like to thank Peter
Panburana for his feedback on technical details of the solution.
Constructive comments were received from Benjamin Kaduk, Eliot Lear,
Jim Schaad, Hannes Tschofenig, Julien Vermillard, John Manuel, Oliver
Pfaff, Pete Beal, and Carsten Bormann.
Interop tests were done by Oliver Pfaff, Thomas Werner, Oskar
Camezind, Bjorn Elmers, and Joel Hoglund.
Robert Moskowitz provided code to create the examples.
Contributors
Martin Furuhed contributed to the EST-coaps specification by
providing feedback based on the Nexus EST-over-CoAPS server
implementation that started in 2015. Sandeep Kumar kick-started this
specification and was instrumental in drawing attention to the
importance of the subject.
Authors' Addresses Authors' Addresses
Peter van der Stok Peter van der Stok
Consultant Consultant
Email: stokcons@bbhmail.nl
Email: consultancy@vanderstok.org
Panos Kampanakis Panos Kampanakis
Cisco Systems Cisco Systems
Email: pkampana@cisco.com Email: pkampana@cisco.com
Michael C. Richardson Michael C. Richardson
Sandelman Software Works Sandelman Software Works
Email: mcr+ietf@sandelman.ca Email: mcr+ietf@sandelman.ca
URI: http://www.sandelman.ca/ URI: https://www.sandelman.ca/
Shahid Raza Shahid Raza
RISE SICS RISE Research Institutes of Sweden
Isafjordsgatan 22 Isafjordsgatan 22
Kista, Stockholm 16440 SE-16440 Kista, Stockholm
SE Sweden
Email: shahid.raza@ri.se
Email: shahid@sics.se
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