draft-ietf-teep-architecture-00.txt   draft-ietf-teep-architecture-01.txt 
TEEP M. Pei TEEP M. Pei
Internet-Draft Symantec Internet-Draft Symantec
Intended status: Informational H. Tschofenig Intended status: Informational H. Tschofenig
Expires: January 3, 2019 Arm Ltd. Expires: April 26, 2019 Arm Limited
D. Wheeler
Intel
A. Atyeo A. Atyeo
Intercede Intercede
D. Liu L. Dapeng
Alibaba Group Alibaba Group
July 2, 2018 October 23, 2018
Trusted Execution Environment Provisioning (TEEP) Architecture Trusted Execution Environment Provisioning (TEEP) Architecture
draft-ietf-teep-architecture-00.txt draft-ietf-teep-architecture-01
Abstract Abstract
A Trusted Execution Environment (TEE) was designed to provide a A Trusted Execution Environment (TEE) is designed to provide a
hardware-isolation mechanism to separate a regular operating system hardware-isolation mechanism to separate a regular operating system
from security- sensitive applications. from security-sensitive application components.
This architecture document motivates the design and standardization This architecture document motivates the design and standardization
of a protocol for managing the lifecyle of trusted applications of a protocol for managing the lifecycle of trusted applications
running inside a TEE. running inside a TEE.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 3, 2019. This Internet-Draft will expire on April 26, 2019.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Scope and Assumptions . . . . . . . . . . . . . . . . . . . . 6 3. Scope and Assumptions . . . . . . . . . . . . . . . . . . . . 7
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Payment . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1. Payment . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. Authentication . . . . . . . . . . . . . . . . . . . . . 7 4.2. Authentication . . . . . . . . . . . . . . . . . . . . . 8
4.3. Internet of Things . . . . . . . . . . . . . . . . . . . 7 4.3. Internet of Things . . . . . . . . . . . . . . . . . . . 9
4.4. Confidential Cloud Computing . . . . . . . . . . . . . . 7 4.4. Confidential Cloud Computing . . . . . . . . . . . . . . 9
5. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 7 5. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. System Components . . . . . . . . . . . . . . . . . . . . 7 5.1. System Components . . . . . . . . . . . . . . . . . . . . 9
5.2. Entity Relations . . . . . . . . . . . . . . . . . . . . 9 5.2. Different Renditions of TEEP Architecture . . . . . . . . 12
5.3. Trust Anchors in TEE . . . . . . . . . . . . . . . . . . 12 5.3. Entity Relations . . . . . . . . . . . . . . . . . . . . 12
5.4. Trust Anchors in TAM . . . . . . . . . . . . . . . . . . 12 5.4. Trust Anchors in TEE . . . . . . . . . . . . . . . . . . 15
5.5. Keys and Certificate Types . . . . . . . . . . . . . . . 12 5.5. Trust Anchors in TAM . . . . . . . . . . . . . . . . . . 15
5.6. Scalability . . . . . . . . . . . . . . . . . . . . . . . 15 5.6. Keys and Certificate Types . . . . . . . . . . . . . . . 15
5.7. Message Security . . . . . . . . . . . . . . . . . . . . 15 5.7. Scalability . . . . . . . . . . . . . . . . . . . . . . . 18
5.8. Security Domain Hierarchy and Ownership . . . . . . . . . 15 5.8. Message Security . . . . . . . . . . . . . . . . . . . . 18
5.9. SD Owner Identification and TAM Certificate Requirements 16 5.9. Security Domain Hierarchy and Ownership . . . . . . . . . 18
5.10. Service Provider Container . . . . . . . . . . . . . . . 17 5.10. SD Owner Identification and TAM Certificate Requirements 19
5.11. A Sample Device Setup Flow . . . . . . . . . . . . . . . 17 5.11. Service Provider Container . . . . . . . . . . . . . . . 20
6. Agent . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.12. A Sample Device Setup Flow . . . . . . . . . . . . . . . 20
6.1. Role of the Agent . . . . . . . . . . . . . . . . . . . . 18 6. TEEP Broker . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.2. Agent Implementation Consideration . . . . . . . . . . . 19 6.1. Role of the Agent . . . . . . . . . . . . . . . . . . . . 22
6.2.1. Agent Distribution . . . . . . . . . . . . . . . . . 19 6.2. Agent Implementation Consideration . . . . . . . . . . . 22
6.2.2. Number of Agents . . . . . . . . . . . . . . . . . . 19 6.2.1. Agent Distribution . . . . . . . . . . . . . . . . . 22
7. Attestation . . . . . . . . . . . . . . . . . . . . . . . . . 20 6.2.2. Number of Agents . . . . . . . . . . . . . . . . . . 23
7.1. Attestation Hierarchy . . . . . . . . . . . . . . . . . . 20 7. Attestation . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.1.1. Attestation Hierarchy Establishment: Manufacture . . 20 7.1. Attestation Hierarchy . . . . . . . . . . . . . . . . . . 23
7.1.2. Attestation Hierarchy Establishment: Device Boot . . 20 7.1.1. Attestation Hierarchy Establishment: Manufacture . . 23
7.1.3. Attestation Hierarchy Establishment: TAM . . . . . . 21 7.1.2. Attestation Hierarchy Establishment: Device Boot . . 24
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 7.1.3. Attestation Hierarchy Establishment: TAM . . . . . . 24
9. Security Consideration . . . . . . . . . . . . . . . . . . . 21 8. Algorithm and Attestation Agility . . . . . . . . . . . . . . 24
9.1. TA Trust Check at TEE . . . . . . . . . . . . . . . . . . 21 9. Security Considerations . . . . . . . . . . . . . . . . . . . 25
9.2. One TA Multiple SP Case . . . . . . . . . . . . . . . . . 22 9.1. TA Trust Check at TEE . . . . . . . . . . . . . . . . . . 25
9.3. Agent Trust Model . . . . . . . . . . . . . . . . . . . . 22 9.2. One TA Multiple SP Case . . . . . . . . . . . . . . . . . 25
9.4. Data Protection at TAM and TEE . . . . . . . . . . . . . 22 9.3. Agent Trust Model . . . . . . . . . . . . . . . . . . . . 25
9.5. Compromised CA . . . . . . . . . . . . . . . . . . . . . 22 9.4. Data Protection at TAM and TEE . . . . . . . . . . . . . 26
9.6. Compromised TAM . . . . . . . . . . . . . . . . . . . . . 22 9.5. Compromised CA . . . . . . . . . . . . . . . . . . . . . 26
9.7. Certificate Renewal . . . . . . . . . . . . . . . . . . . 23 9.6. Compromised TAM . . . . . . . . . . . . . . . . . . . . . 26
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 9.7. Certificate Renewal . . . . . . . . . . . . . . . . . . . 26
10.1. Normative References . . . . . . . . . . . . . . . . . . 23 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
10.2. Informative References . . . . . . . . . . . . . . . . . 23 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
12.1. Normative References . . . . . . . . . . . . . . . . . . 27
12.2. Informative References . . . . . . . . . . . . . . . . . 27
Appendix A. History . . . . . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction 1. Introduction
The Trusted Execution Environment (TEE) concept has been designed to Applications executing in a device are exposed to many different
separate a regular operating system, also referred as a Rich attacks intended to compromise the execution of the application, or
Execution Environment (REE), from security- sensitive applications. reveal the data upon which those applications are operating. These
A TEE provides hardware-enforcement so that any data inside the TEE attacks increase with the number of other applications on the device,
cannot be read by code outside of the TEE. Compromising a REE and with such other applications coming from potentially untrustworthy
normal applications in the REE do not affect code inside the TEE, sources. The potential for attacks further increase with the
which is called a Trusted Application (TA), running inside the TEE. complexity of features and applications on devices, and the
unintended interactions among those features and applications. The
danger of attacks on a system increases as the sensitivity of the
applications or data on the device increases. As an example,
exposure of emails from a mail client is likely to be of concern to
its owner, but a compromise of a banking application raises even
greater concerns.
In an TEE ecosystem, a Trusted Application Manager (TAM) is commonly The Trusted Execution Environment (TEE) concept is designed to
used to manage keys and TAs that run in a device. Different device execute applications in a protected environment that separates
vendors may use different TEE implementations. Different application applications inside the TEE from the regular operating system and
providers or device administrators may choose to use different TAM from other applications on the device. This separation reduces the
providers. possibility of a successful attack on application components and the
data contained inside the TEE. Typically, application components are
chosen to execute inside a TEE because those application components
perform security sensitive operations or operate on sensitive data.
To simplify the life of developers an interoperable protocol for An application component running inside a TEE is referred to as a
managing TAs running in different TEEs of various devices is needed. Trusted Application (TA), while a normal application running in the
regular operating system is referred to as an Untrusted Application
(UA).
The protocol addresses the following problems. The TEE uses hardware to enforce protections on the TA and its data,
but also presents a more limited set of services to applications
inside the TEE than is normally available to UA's running in the
normal operating system.
1. A Device Administrator (DA) or Service Provider (SP) of the But not all TEEs are the same, and different vendors may have
device users needs to determine security-relevant information of different implementations of TEEs with different security properties,
a device before provisioning the TA to the device with a TEE. different features, and different control mechanisms to operate on
Examples include the verification of the device 'root of trust' TAs. Some vendors may themselves market multiple different TEEs with
and the type of TEE included in a device. different properties attuned to different markets. A device vendor
may integrate one or more TEEs into their devices depending on market
needs.
2. A TEE in a device needs to determine whether a Device To simplify the life of developers and service providers interacting
Administrator (DA) or a Service Provider (SP) that wants to with TAs in a TEE, an interoperable protocol for managing TAs running
manage an TA in the device is authorized to manage applications in different TEEs of various devices is needed. In this TEE
in the TEE. ecosystem, there often arises a need for an external trusted party to
verify the identity, claims, and rights of Service Providers(SP),
devices, and their TEEs. This trusted third party is the Trusted
Application Manager (TAM).
3. Attestation must be able to ensure a TEE is genuine. This protocol addresses the following problems:
- A Service Provider (SP) intending to provide services through a TA
to users of a device needs to determine security-relevant
information of a device before provisioning their TA to the TEE
within the device. Examples include the verification of the
device 'root of trust' and the type of TEE included in a device.
- A TEE in a device needs to determine whether a Service Provider
(SP) that wants to manage a TA in the device is authorized to
manage TAs in the TEE, and what TAs the SP is permitted to manage.
- The parties involved in the protocol must be able to attest that a
TEE is genuine and capable of providing the security protections
required by a particular TA.
- A Service Provider (SP) must be able to deterine if a TA exists
(is installed) on a device (in the TEE), and if not, install the
TA in the TEE.
- A Service Provider (SP) must be able to check whether a TA in a
device's TEE is the most up-to-date version, and if not, update
the TA in the TEE.
- A Service Provider (SP) must be able to remove a TA in a device's
TEE if the SP is no longer offering such services or the services
are being revoked from a particular user (or device). For
example, if a subscription or contract for a particular service
has expired, or a payment by the user has not been completed or
has been recinded.
- A Service Provider (SP) must be able to define the relationship
between cooperating TAs under the SP's control, and specify
whether the TAs can communicate, share data, and/or share key
material.
2. 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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in RFC 2119 [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Client Application: An application running on a rich OS, such as an The following terms are used:
Android, Windows, or iOS application.
Device: A physical piece of hardware that hosts a TEE along with a - Client Application: An application running in a Rich Execution
rich OS. Environment, such as an Android, Windows, or iOS application.
Agent: An application running in the rich OS allowing the message - Device: A physical piece of hardware that hosts a TEE along with a
protocol exchange between a TAM and a TEE in a device. A TEE is Rich Execution Environment. A Device contains a default list of
responsible to processing relayed messages and for returning an Trust Anchors that identify entities (e.g., TAMs) that are trusted
appropriate reponse. by the Device. This list is normally set by the Device
Manufacturer, and may be governed by the Device's network carrier.
The list of Trust Anchors is normally modifiable by the Device's
owner or Device Administrator. However the Device manufacturer
and network carrier may restrict some modifications, for example,
by not allowing the manufacturer or carrier's Trust Anchor to be
removed or disabled.
Rich Execution Environment (REE) An environment that is provided and - Rich Execution Environment (REE): An environment that is provided
governed by a typical OS (Linux, Windows, Android, iOS, etc.), and governed by a typical OS (e.g., Linux, Windows, Android, iOS),
potentially in conjunction with other supporting operating potentially in conjunction with other supporting operating systems
systems and hypervisors; it is outside of the TEE. This and hypervisors; it is outside of the TEE. This environment and
environment and applications running on it are considered un- applications running on it are considered un-trusted.
trusted.
Secure Boot Module (SBM): A firmware in a device that delivers - Service Provider (SP): An entity that wishes to provide a service
secure boot functionality. It is generally signed and can be on Devices that requires the use of one or more Trusted
verified whether it can be trusted. Applications. A Service Provider requires the help of a TAM in
order to provision the Trusted Applications to remote devices.
Service Provider (SP): An entity that wishes to supply Trusted - Device Administrator: An entity that owns or is responsible for
Applications to remote devices. A Service Provider requires the administration of a Device. A Device Administrator has privileges
help of a TAM in order to provision the Trusted Applications to on the Device to install and remove applications and TAs, approve
the devices. or reject Trust Anchors, and approve or reject Service Providers,
among possibly other privileges on the Device. A device owner can
manage the list of allowed TAMs by modifying the list of Trust
Anchors on the Device. Although a Device Administrator may have
privileges and Device-specific controls to locally administer a
device, the Device Administrator may choose to remotely
administrate a device through a TAM.
Trust Anchor: A root certificate that can be used to validate its - Trust Anchor: A public key in a device whose corresponding private
children certificates. It is usually embedded in a device or key is held by an entity implicitly trusted by the device. The
configured by a TAM for validating the trust of a remote entity's Trust Anchor may be a certificate or it may be a raw public key.
certificate. The trust anchor is normally stored in a location that resists
unauthorized modification, insertion, or replacement.
The trust anchor private key owner can sign certificates of other
public keys, which conveys trust about those keys to the device.
A certificate signed by the trust anchor communicates that the
private key holder of the signed certificate is trusted by the
trust anchor holder, and can therefore be trusted by the device.
Trusted Application (TA): An Application that runs in a TEE. - Trusted Application (TA): An application component that runs in a
TEE.
Trusted Execution Environment (TEE): An execution environment that - Trusted Execution Environment (TEE): An execution environment that
runs alongside of, but is isolated from, an REE. A TEE has runs alongside of, but is isolated from, an REE. A TEE has
security capabilities and meets certain security-related security capabilities and meets certain security-related
requirements. It protects TEE assets from general software requirements. It protects TEE assets from general software
attacks, defines rigid safeguards as to data and functions that a attacks, defines rigid safeguards as to data and functions that a
program can access, and resists a set of defined threats. It program can access, and resists a set of defined threats. It
should have at least the following three properties: should have at least the following three properties:
(a) A device unique credential that cannot be cloned; (a) A device unique credential that cannot be cloned;
(b) Assurance that only authorized code can run in the TEE; (b) Assurance that only authorized code can run in the TEE;
(c) Memory that cannot be read by code outside of TEE. (c) Memory that cannot be read by code outside the TEE.
There are multiple technologies that can be used to implement a There are multiple technologies that can be used to implement a
TEE, and the level of security achieved varies accordingly. TEE, and the level of security achieved varies accordingly.
Trusted Firmware (TFW): A signed SBM firmware that can be verified - Root-of-Trust (RoT): A hardware or software component in a device
and is trusted by a TEE in a device. that is inherently trusted to perform a certain security-critical
function. A RoT should be secure by design, small, and protected
by hardware against modification or interference. Examples of
RoTs include software/firmware measurement and verification using
a trust anchor (RoT for Verification), provide signed assertions
using a protected attestation key (RoT for Reporting), or protect
the storage and/or use of cryptographic keys (RoT for Storage).
Other RoTs are possible, including RoT for Integrity, and RoT for
Measurement. Reference: NIST SP800-164 (Draft).
- Trusted Firmware (TFW): A firmware in a device that can be
verified with a trust anchor by RoT for Verification.
- Bootloader key: This symmetric key is protected by
electronic fuse (eFUSE) technology. In this context it is used to
decrypt a
TFW private key, which belongs to a device-unique private/public
key pair. Not every device is equipped with a bootloader key.
This document uses the following abbreviations: This document uses the following abbreviations:
CA Certificate Authority - CA: Certificate Authority
REE Rich Execution Environment - REE: Rich Execution Environment
SD Security Domain - RoT: Root of Trust
SP Service Provider - SD: Security Domain
SBM Secure Boot Module - SP: Service Provider
TA Trusted Application - TA: Trusted Application
TEE Trusted Execution Environment - TAM: Trusted Application Manager
TFW Trusted Firmware - TEE: Trusted Execution Environment
TAM Trusted Application Manager - TFW: Trusted Firmware
3. Scope and Assumptions 3. Scope and Assumptions
This specification assumes that an applicable device is equipped with This specification assumes that an applicable device is equipped with
one or more TEEs and each TEE is pre-provisioned with a device-unique one or more TEEs and each TEE is pre-provisioned with a device-unique
public/private key pair, which is securely stored. This key pair is public/private key pair, which is securely stored. This key pair is
referred to as the 'root of trust' for remote attestation of the referred to as the 'root of trust' for remote attestation of the
associated TEE in a device by an TAM. associated TEE in a device by an TAM.
New note: SD is for managing keys for TAs
A Security Domain (SD) concept is used as the security boundary A Security Domain (SD) concept is used as the security boundary
inside a TEE for trusted applications. Each SD is typically inside a TEE for trusted applications. Each SD is typically
associated with one TA provider as the owner, which is a logical associated with one TA provider as the owner, which is a logical
space that contains a SP's TAs. One TA provider may request to have space that contains an SP's TAs. One TA provider may request to have
multiple SDs in a TEE. One SD may contain multiple TAs. Each multiple SDs in a TEE. One SD may contain multiple TAs. Each
Security Domain requires the management operations of TAs in the form Security Domain requires the management operations of TAs in the form
of installation, update and deletion. of installation, update and deletion.
A TA binary and configuration data can be from two sources: Each TA binary and configuration data can be from either of two
sources:
1. A TAM supplies the signed and encrypted TA binary 1. A TAM supplies the signed and encrypted TA binary and any
required configuration data
2. A Client Application supplies the TA binary 2. A Client Application supplies the TA binary
The architecture covers the first case where the TA binary and The architecture covers the first case where the TA binary and
configuration data are delivered from a TAM. The second case calls configuration data are delivered from a TAM. The second case calls
for an extension when a TAM is absent. for an extension when a TAM is absent.
Messages exchange with a TAM require some transport and HTTPS is one
commonly used transport.
4. Use Cases 4. Use Cases
4.1. Payment 4.1. Payment
A payment application in a mobile device requires high security and A payment application in a mobile device requires high security and
trust about the hosting device. Payments initiated from a mobile trust about the hosting device. Payments initiated from a mobile
device can use a Trusted Application running inside TEE in the device device can use a Trusted Application to provide strong identification
to provide strong identification and proof of transaction. and proof of transaction.
For a mobile payment application, some biometric identification For a mobile payment application, some biometric identification
information could also be stored in the TEE. The mobile payment information could also be stored in a TEE. The mobile payment
application can use such information for authentication. application can use such information for authentication.
A secure user interface (UI) may be used in a mobile device to A secure user interface (UI) may be used in a mobile device to
prevent malicious software from stealing sensitive user input data. prevent malicious software from stealing sensitive user input data.
Such an application implementation often relies on TEE for user input Such an application implementation often relies on a TEE for user
protection. input protection.
4.2. Authentication 4.2. Authentication
For better security of authentication, a devices may store its For better security of authentication, a device may store its
sensitive authentication keys inside a TEE of the device, providing sensitive authentication keys inside a TEE, providing hardware-
hardware-protected security key strength and trusted execution code. protected security key strength and trusted code execution.
4.3. Internet of Things 4.3. Internet of Things
Internet of Things (IoT) has been posing threats to networks and The Internet of Things (IoT) has been posing threats to networks and
national infrastructures because of existing weak security in national infrastructures because of existing weak security in
devices. It is very desirable that IoT devices can prevent a malware devices. It is very desirable that IoT devices can prevent malware
from stealing or modifying sensitive data such as authentication from manipulating actuators (e.g., unlocking a door), or stealing or
credentials in the device. A TEE can be the best way to implement modifying sensitive data such as authentication credentials in the
such IoT security functions. device. A TEE can be the best way to implement such IoT security
functions.
TEEs could be used to store variety of sensitive data for IoT TEEs could be used to store variety of sensitive data for IoT
devices. For example, a TEE could be used in smart door locks to devices. For example, a TEE could be used in smart door locks to
store a user's biometric information for identification, and for store a user's biometric information for identification, and for
protecting access the locking mechanism. Bike-sharing is another protecting access the locking mechanism.
example that shares a similar usage scenario.
4.4. Confidential Cloud Computing 4.4. Confidential Cloud Computing
A tenant can store sensitive data in a TEE in a cloud computing A tenant can store sensitive data in a TEE in a cloud computing
server such that only the tenant can access the data, preventing the server such that only the tenant can access the data, preventing the
cloud host provider from accessing the data. A tenant can run TAs cloud hosting provider from accessing the data. A tenant can run TAs
inside a server TEE for secure operation and enhanced data security. inside a server TEE for secure operation and enhanced data security.
This provides benefits not only to tenants with better data security This provides benefits not only to tenants with better data security
but also to cloud host provider for reduced liability and increased but also to cloud hosting provider for reduced liability and
cloud adoption. increased cloud adoption.
5. Architecture 5. Architecture
5.1. System Components 5.1. System Components
The following are the main components in the system. The following are the main components in the system. Full
descriptions of components not previously defined are provided below.
Interactions of all components are further explained in the following
paragraphs.
TAM: A TAM is responsible for originating and coordinating lifecycle +-------------------------------------------+
management activity on a particular TEE on behalf of a Service | Device |
Provider or a Device Administrator. For example, a payment | +--------+ | Service Provider
application provider, which also provides payment service as a | | |----------+ |
Service Provider using its payment TA, may choose to use a TAM | +-------------+ | TEEP |---------+| |
that it runs or a third party TAM service to distribute and | | TEE-1 |<------| Broker | | || +--------+ |
update its payment TA application in payment user devices. The | | | | |<---+ | |+-->| |<-+
payment SP isn't a device administrator of the user devices. A | | | | | | | | +-| TAM-1 |
user who chooses to download the payment TA into its devices acts | | | | |<-+ | | +->| | |<-+
as the device administrator, authorizing the TA installation via | | +---+ +---+ | +--------+ | | | | +--------+ |
the downloading consent. The device manufacturer is typically | | |TA1| |TA2| | | | | | TAM-2 | |
responsible for embedding the TAM trust verification capability | +-->| | | | | +-------+ | | | +--------+ |
in its device TEE. | | | | | | |<---------| App-2 |--+ | | |
| | | +---+ +---+ | +-------+ | | | Device Administrator
| | +-------------+ | App-1 | | | |
| | | | | | |
| +--------------------| |---+ | |
| | |--------+ |
| +-------+ |
+-------------------------------------------+
A TAM may be used by one SP or many SPs where a TAM may run as a Figure 1: Notional Architecture of TEEP
Software-as-a-Service (SaaS). A TAM may provide Security Domain
management and TA management in a device for the SD and TAs that
a SP owns. In particular, a TAM typically offers over-the-air
update to keep a SP's TAs up-to-date and clean up when a version
should be removed. A TEE administrator or device administrator
may decide TAMs that it trusts to manage its devices.
Certification Authority (CA): Certificate-based credentials used for - Service Providers and Device Administrators utilize the services
authenticating a device, a TAM and an SP. A device embeds a list of a TAM to manage TAs on Devices. SPs do not directly interact
of root certificates (trust anchors), from trusted CAs that a TAM with devices. DAs may elect to use a TAM for remote
will be validated against. A TAM will remotely attest a device administration of TAs instead of managing each device directly.
by checking whether a device comes with a certificate from a CA
that the TAM trusts. The CAs do not need to be the same;
different CAs can be chosen by each TAM, and different device CAs
can be used by different device manufacturers.
TEE: A TEE in a device is responsible for protecting applications - TAM: A TAM is responsible for performing lifecycle management
from attack, enabling the application to perform secure activity on TA's and SD's on behalf of Service Providers and
operations. Device Administrators. This includes creation and deletion of
TA's and SD's, and may include, for example, over-the-air updates
to keep an SP's TAs up-to-date and clean up when a version should
be removed. TAMs may provide services that make it easier for SPs
or DAs to use the TAM's service to manage multiple devices,
although that is not required of a TAM.
REE: The REE in a device is responsible for enabling off-device The TAM performs its management of TA's and SD's through an
communications to be established between a TEE and TAM. The interaction with a Device's TEEP Broker. As shown in
architecture does not assume or require that the REE or Client #notionalarch, the TAM cannot directly contact a Device, but must
Applications is secure. wait for a the TEEP Broker or a Client Application to contact the
TAM requesting a particular service. This architecture is
intentional in order to accommodate network and application
firewalls that normally protect user and enterprise devices from
arbitrary connections from external network entities.
Agent: A Client Application is expected to communicate with a TAM to A TAM may be publically available for use by many SPs, or a TAM
request TAs that it needs to use. The Client Application needs may be private, and accessible by only one or a limited number of
to pass the messages from the TAM to TEEs in the device. This SPs. It is expected that manufacturers and carriers will run
calls for a component in REE that the Client Application can use their own private TAM. Another example of a private TAM is a TAM
to pass messages to TEEs. An Agent is this component to fill the running as a Software-as-a-Service (SaaS) within an SP.
role. In other words, an Agent is an application in the REE or
software library that can simply relays messages from a Client
Application to a TEE in the device. A device usually comes with
only one active TEE. A TEE that supports may provide such an
Agent to the device manufacturer to be bundled in devices. Such
a compliant TEE must also include an Agent counterpart, namely, a
processing module inside the TEE, to parse TAM messages sent
through the Agent. An Agent is generally acting as a dummy
relaying box with just the TEE interacting capability; it doesn't
need and shouldn't parse protocol messages.
Device Administrator: A device owner or administrator may want to A SP or Device Administrator chooses a particular TAM based on
manage what TAs allowed to run in its devices. A default list of whether the TAM is trusted by a Device or set of Devices. The TAM
allowed TA trust root CA certificates is included in a device by is trusted by a device if the TAM's public key is an authorized
the device's manufacturer, which may be governed by the device Trust Anchor in the Device. A SP or Device Administrator may run
carriers sometimes. There may be needs to expose overriding their own TAM, however the Devices they wish to manage must
capability for a device owner to decide the list of allowed TAs include this TAM's pubic key in the Trust Anchor list.
by updating the list of trusted CA certificates.
Secure Boot: Secure boot must enable authenticity checking of TEEs A SP or Device Administrator is free to utilize multiple TAMs.
by the TAM. Note that some TEE implementations do not require This may be required for a SP to manage multiple different types
secure boot functionality. of devices from different manufacturers, or devices on different
carriers, since the Trust Anchor list on these different devices
may contain different TAMs. A Device Administrator may be able to
add their own TAM's public key or certificate to the Trust Anchor
list on all their devices, overcoming this limitation.
5.2. Entity Relations Any entity is free to operate a TAM. For a TAM to be successful,
it must have its public key or certificate installed in Devices
Trust Anchor list. A TAM may set up a relationship with device
manufacturers or carriers to have them install the TAM's keys in
their device's Trust Anchor list. Alternatively, a TAM may
publish its certificate and allow Device Administrators to install
the TAM's certificate in their devices as an after-market-action.
- TEEP Broker: The TEEP Broker is an application running in a Rich
Execution Environment that enables the message protocol exchange
between a TAM and a TEE in a device. The TEEP Broker does not
process messages on behalf of a TEE, but merely is responsible for
relaying messages from the TAM to the TEE, and for returning the
TEE's responses to the TAM.
A Client Application is expected to communicate with a TAM to
request TAs that it needs to use. The Client Application needs to
pass the messages from the TAM to TEEs in the device. This calls
for a component in the REE that Client Applications can use to
pass messages to TEEs. An Agent is thus an application in the REE
or software library that can relay messages from a Client
Application to a TEE in the device. A device usually comes with
only one active TEE. A TEE may provide such an Agent to the
device manufacturer to be bundled in devices. Such a TEE must
also include an Agent counterpart, namely, a processing module
inside the TEE, to parse TAM messages sent through the Agent. An
Agent is generally acting as a dummy relaying box with just the
TEE interacting capability; it doesn't need and shouldn't parse
protocol messages.
- Certification Authority (CA): Certificate-based credentials used
for authenticating a device, a TAM and an SP. A device embeds a
list of root certificates (trust anchors), from trusted CAs that a
TAM will be validated against. A TAM will remotely attest a
device by checking whether a device comes with a certificate from
a CA that the TAM trusts. The CAs do not need to be the same;
different CAs can be chosen by each TAM, and different device CAs
can be used by different device manufacturers.
5.2. Different Renditions of TEEP Architecture
5.3. Entity Relations
This architecture leverages asymmetric cryptography to authenticate a This architecture leverages asymmetric cryptography to authenticate a
device towards a TAM. Additionally, a TEE in a device authenticates device to a TAM. Additionally, a TEE in a device authenticates a TAM
a TAM provider and TA signer. The provisioning of trust anchors to a and TA signer. The provisioning of trust anchors to a device may
device may different from one use case to the other. The device different from one use case to the other. A device administrator may
administrator may want to have the capability to control what TAs are want to have the capability to control what TAs are allowed. A
allowed. A device manufacturer enables verification of the TA device manufacturer enables verification of the TA signers and TAM
signers and TAM providers; it may embed a list of default trust providers; it may embed a list of default trust anchors that the
anchors that the signer of an allowed TA's signer certificate should signer of an allowed TA's signer certificate should chain to. A
chain to. A device administrator may choose to accept a subset of device administrator may choose to accept a subset of the allowed TAs
the allowed TAs via consent or action of downloading. via consent or action of downloading.
PKI CA -- CA CA -- PKI CA -- CA CA --
| | | | | |
| | | | | |
| | | | | |
Device | | --- Agent / Client App --- | Device | | --- Agent / Client App --- |
SW | | | | | SW | | | | |
| | | | | | | | | |
| | | | | | | | | |
| -- TEE TAM------- | -- TEE TAM-------
| |
| |
FW FW
Figure 1: Entities Figure 2: Entities
(App Developer) (App Store) (TAM) (Device with TEE) (CAs) (App Developer) (App Store) (TAM) (Device with TEE) (CAs)
| | | |
| --> (Embedded TEE cert) <-- | --> (Embedded TEE cert) <--
| | | |
| <------------------------------ Get an app cert ----- | | <------------------------------ Get an app cert ----- |
| | <-- Get a TAM cert ------ | | | <-- Get a TAM cert ------ |
| |
1. Build two apps: 1. Build two apps:
Client App Client App
TA TA
| |
| |
Client App -- 2a. --> | ----- 3. Install -------> | Client App -- 2a. --> | ----- 3. Install -------> |
TA ------- 2b. Supply ------> | 4. Messaging-->| TA ------- 2b. Supply ------> | 4. Messaging-->|
| | | | | | | |
Figure 2: Developer Experience Figure 3: Developer Experience
Figure 2 shows an application developer building two applications: 1) Figure 3 shows an application developer building two applications: 1)
a rich Client Application; 2) a TA that provides some security a rich Client Application; 2) a TA that provides some security
functions to be run inside a TEE. At step 2, the application functions to be run inside a TEE. At step 2, the application
developer uploads the Client Application (2a) to an Application developer uploads the Client Application (2a) to an Application
Store. The Client Application may optionally bundle the TA binary. Store. The Client Application may optionally bundle the TA binary.
Meanwhile, the application developer may provide its TA to a TAM Meanwhile, the application developer may provide its TA to a TAM
provider that will be managing the TA in various devices. 3. A user provider that will be managing the TA in various devices. 3. A user
will go to an Application Store to download the Client Application. will go to an Application Store to download the Client Application.
The Client Application will trigger TA installation by calling TAM. The Client Application will trigger TA installation by initiating
This is the step 4. The Client Application will get messages from communication with a TAM. This is the step 4. The Client
TAM, and interacts with device TEE via an Agent. Application will get messages from TAM, and interacts with device TEE
via an Agent.
The following diagram will show a system diagram about the entity The following diagram shows a system diagram about the entity
relationships between CAs, TAM, SP and devices. relationships between CAs, TAMs, SPs and devices.
------- Message Protocol ----- ------- Message Protocol -----
| | | |
| | | |
-------------------- --------------- ---------- -------------------- --------------- ----------
| REE | TEE | | TAM | | SP | | REE | TEE | | TAM | | SP |
| --- | --- | | --- | | -- | | --- | --- | | --- | | -- |
| | | | | | | | | | | | | |
| Client | SD (TAs)| | SD / TA | | TA | | Client | SD (TAs)| | SD / TA | | TA |
| Apps | | | Mgmt | | | | Apps | | | Mgmt | | |
| | | | | | | | | | | | | | | |
| | | | | | | | | | | List of | | List of | | |
| | Trusted | | Trusted | | | | | Trusted | | Trusted | | |
| Agent | TAM/SP | | FW/TEE | | | | Agent | TAM/SP | | FW/TEE | | |
| | CAs | | CAs | | | | | CAs | | CAs | | |
| | | | | | | | | | | | | |
| |TEE Key/ | | TAM Key/ | |SP Key/ | | |TEE Key/ | | TAM Key/ | |SP Key/ |
| | Cert | | Cert | | Cert | | | Cert | | Cert | | Cert |
| | FW Key/ | | | | | | | FW Key/ | | | | |
| | Cert | | | | | | | Cert | | | | |
-------------------- --------------- ---------- -------------------- --------------- ----------
| | | | | |
| | | | | |
------------- ---------- --------- ------------- ---------- ---------
| TEE CA | | TAM CA | | SP CA | | TEE CA | | TAM CA | | SP CA |
------------- ---------- --------- ------------- ---------- ---------
Figure 3: Keys Figure 4: Keys
In the previous diagram, different CAs can be used for different In the previous diagram, different CAs can be used for different
types of certificates. Messages are always signed, where the signer types of certificates. Messages are always signed, where the signer
key is the message originator's private key such as that of a TAM, key is the message originator's private key such as that of a TAM,
the private key of a trusted firmware (TFW), or a TEE's private key. the private key of trusted firmware (TFW), or a TEE's private key.
The main components consist of a set of standard messages created by The main components consist of a set of standard messages created by
a TAM to deliver device SD and TA management commands to a device, a TAM to deliver device SD and TA management commands to a device,
and device attestation and response messages created by a TEE that and device attestation and response messages created by a TEE that
responds to a TAM's message. responds to a TAM's message.
It should be noted that network communication capability is generally It should be noted that network communication capability is generally
not available in TAs in today's TEE-powered devices. The networking not available in TAs in today's TEE-powered devices. The networking
functionality must be delegated to a rich Client Application. Client functionality must be delegated to a rich Client Application. Client
Applications will need to rely on an agent in the REE to interact Applications will need to rely on an agent in the REE to interact
with a TEE for message exchanges. Consequently, a TAM generally with a TEE for message exchanges. Consequently, a TAM generally
communicates with a Client Application about how it gets messages communicates with a Client Application about how it gets messages
that originates from TEE inside a device. Similarly, a TA or TEE that originate from a TEE inside a device. Similarly, a TA or TEE
generally gets messages from a TAM via some Client Application, generally gets messages from a TAM via some Client Application,
namely, an agent in this protocol architecture, not directly from the namely, an agent in this protocol architecture, not directly from the
internet. network.
It is imperative to have an interoperable protocol to communicate It is imperative to have an interoperable protocol to communicate
with different TEEs in different devices that a Client Application with different TAMs and different TEEs in different devices. This is
needs to run and access a TA inside a TEE. This is the role of the the role of the agent, which is a software component that bridges
agent, which is a software component that bridges communication communication between a TAM and a TEE. The agent does not need to
between a TAM and a TEE. The agent does not need to know the actual know the actual content of messages except for the TEE routing
content of messages except for the TEE routing information. information.
5.3. Trust Anchors in TEE 5.4. Trust Anchors in TEE
Each TEE comes with a trust store that contains a whitelist of root Each TEE comes with a trust store that contains a whitelist of root
CA certificates that are used to validate a TAM's certificate. A TEE CA certificates that are used to validate a TAM's certificate. A TEE
will accept a TAM to create new Security Domains and install new TAs will accept a TAM to create new Security Domains and install new TAs
on behalf of a SP only if the TAM's certificate is chained to one of on behalf of an SP only if the TAM's certificate is chained to one of
the root CA certificates in the TEE's trust store. the root CA certificates in the TEE's trust store.
A TEE's trust store is typically preloaded at manufacturing time. It A TEE's trust store is typically preloaded at manufacturing time. It
is out of the scope in this document to specify how the trust store is out of the scope in this document to specify how the trust store
should be updated when a new root certificate should be added or should be updated when a new root certificate should be added or
existing one should be updated or removed. A device manufacturer is existing one should be updated or removed. A device manufacturer is
expected to provide its TEE trust store live update or out-of-band expected to provide its TEE trust store live update or out-of-band
update to devices. update to devices.
Before a TAM can begin operation in the marketplace to support TEE- Before a TAM can begin operation in the marketplace to support a
powered devices with a particular TEE, it must obtain a TAM device with a particular TEE, it must obtain a TAM certificate from a
certificate from a CA that is listed in the trust store of the TEE. CA that is listed in the trust store of the TEE.
5.4. Trust Anchors in TAM 5.5. Trust Anchors in TAM
The trust anchor store in a TAM consists of a list of CA certificates The trust anchor store in a TAM consists of a list of CA certificates
that sign various device TEE certificates. A TAM decides what that sign various device TEE certificates. A TAM decides what
devices it will trust the TEE in. devices it will trust the TEE in.
5.5. Keys and Certificate Types 5.6. Keys and Certificate Types
This architecture leverages the following credentials, which allow This architecture leverages the following credentials, which allow
delivering end-to-end security without relying on any transport delivering end-to-end security without relying on any transport
security. security.
+-------------+----------+--------+-------------------+-------------+ +-------------+----------+--------+-------------------+-------------+
| Key Entity | Location | Issuer | Checked Against | Cardinality | | Key Entity | Location | Issuer | Checked Against | Cardinality |
| Name | | | | | | Name | | | | |
+-------------+----------+--------+-------------------+-------------+ +-------------+----------+--------+-------------------+-------------+
| 1. TFW key | Device | FW CA | A white list of | 1 per | | 1. TFW key | Device | FW CA | A whitelist of | 1 per |
| pair and | secure | | FW root CA | device | | pair and | secure | | FW root CA | device |
| certificate | storage | | trusted by TAMs | | | certificate | storage | | trusted by TAMs | |
| | | | | | | | | | | |
| 2. TEE key | Device | TEE CA | A white list of | 1 per | | 2. TEE key | Device | TEE CA | A whitelist of | 1 per |
| pair and | TEE | under | TEE root CA | device | | pair and | TEE | under | TEE root CA | device |
| certificate | | a root | trusted by TAMs | | | certificate | | a root | trusted by TAMs | |
| | | CA | | | | | | CA | | |
| | | | | | | | | | | |
| 3. TAM key | TAM | TAM CA | A white list of | 1 or | | 3. TAM key | TAM | TAM CA | A whitelist of | 1 or |
| pair and | provider | under | TAM root CA | multiple | | pair and | provider | under | TAM root CA | multiple |
| certificate | | a root | embedded in TEE | can be used | | certificate | | a root | embedded in TEE | can be used |
| | | CA | | by a TAM | | | | CA | | by a TAM |
| | | | | | | | | | | |
| 4. SP key | SP | SP | A SP uses a TAM. | 1 or | | 4. SP key | SP | SP | A SP uses a TAM. | 1 or |
| pair and | | signer | TA is signed by a | multiple | | pair and | | signer | TA is signed by a | multiple |
| certificate | | CA | SP signer. TEE | can be used | | certificate | | CA | SP signer. TEE | can be used |
| | | | delegates trust | by a TAM | | | | | delegates trust | by a TAM |
| | | | of TA to TAM. SP | | | | | | of TA to TAM. SP | |
| | | | signer is | | | | | | signer is | |
| | | | associated with a | | | | | | associated with a | |
| | | | SD as the owner. | | | | | | SD as the owner. | |
+-------------+----------+--------+-------------------+-------------+ +-------------+----------+--------+-------------------+-------------+
Table 1: Key and Certificate Types Figure 5: Key and Certificate Types
1. TFW key pair and certificate: A key pair and certificate for 1. TFW key pair and certificate: A key pair and certificate for
evidence of secure boot and trustworthy firmware in a device. evidence of trustworthy firmware in a device. This key pair is
optional for TEEP architecture. Some TEE may present its trusted
attributes to a TAM using signed attestation with a TFW key. For
example, a platform that uses a hardware based TEE can have
attestation data signed by a hardware protected TFW key.
Location: Device secure storage o Location: Device secure storage
Supported Key Type: RSA and ECC o Supported Key Type: RSA and ECC
Issuer: OEM CA o Issuer: OEM CA
Checked Against: A white list of FW root CA trusted by TAMs o Checked Against: A whitelist of FW root CA trusted by TAMs
Cardinality: One per device o Cardinality: One per device
2. TEE key pair and certificate: It is used for device attestation 2. TEE key pair and certificate: It is used for device attestation
to a remote TAM and SP. to a remote TAM and SP.
This key pair is burned into the device at device manufacturer. o This key pair is burned into the device by the device
The key pair and its certificate are valid for the expected manufacturer. The key pair and its certificate are valid for
lifetime of the device. the expected lifetime of the device.
Location: Device TEE o Location: Device TEE
Supported Key Type: RSA and ECC o Supported Key Type: RSA and ECC
Issuer: A CA that chains to a TEE root CA o Issuer: A CA that chains to a TEE root CA
Checked Against: A white list of TEE root CA trusted by TAMs o Checked Against: A whitelist of TEE root CAs trusted by TAMs
Cardinality: One per device o Cardinality: One per device
3. TAM key pair and certificate: A TAM provider acquires a 3. TAM key pair and certificate: A TAM provider acquires a
certificate from a CA that a TEE trusts. certificate from a CA that a TEE trusts.
Location: TAM provider o Location: TAM provider
Supported Key Type: RSA and ECC. o Supported Key Type: RSA and ECC.
Supported Key Size: RSA 2048-bit, ECC P-256 and P-384. Other o Supported Key Size: RSA 2048-bit, ECC P-256 and P-384. Other
sizes should be anticipated in future. sizes should be anticipated in future.
Issuer: TAM CA that chains to a root CA o Issuer: TAM CA that chains to a root CA
Checked Against: A white list of TAM root CA embedded in TEE o Checked Against: A whitelist of TAM root CAs embedded in a TEE
Cardinality: One or multiple can be used by a TAM o Cardinality: One or multiple can be used by a TAM
4. SP key pair and certificate: an SP uses its own key pair and 4. SP key pair and certificate: An SP uses its own key pair and
certificate to sign a TA. certificate to sign a TA.
Location: SP o Location: SP
Supported Key Type: RSA and ECC o Supported Key Type: RSA and ECC
Supported Key Size: RSA 2048-bit, ECC P-256 and P-384. Other o Supported Key Size: RSA 2048-bit, ECC P-256 and P-384. Other
sizes should be anticipated in future. sizes should be anticipated in future.
Issuer: an SP signer CA that chains to a root CA o Issuer: An SP signer CA that chains to a root CA
Checked Against: A SP uses a TAM. A TEE trusts an SP by o Checked Against: An SP uses a TAM. A TEE trusts an SP by
validating trust against a TAM that the SP uses. A TEE trusts validating trust against a TAM that the SP uses. A TEE trusts
TAM to ensure that a TA from the TAM is trustworthy. a TAM to ensure that a TA is trustworthy.
Cardinality: One or multiple can be used by an SP o Cardinality: One or multiple can be used by an SP
5.6. Scalability 5.7. Scalability
This architecture uses a PKI. Trust anchors exist on the devices to This architecture uses a PKI. Trust anchors exist on the devices to
enable the TEE to authenticate TAMs, and TAMs use trust anchors to enable the TEE to authenticate TAMs, and TAMs use trust anchors to
authenticate TEEs. Since a PKI is used, many intermediate CAs authenticate TEEs. Since a PKI is used, many intermediate CA
certificates can chain to a root certificate, each of which can issue certificates can chain to a root certificate, each of which can issue
many certificates. This makes the protocol highly scalable. New many certificates. This makes the protocol highly scalable. New
factories that produce TEEs can join the ecosystem. In this case, factories that produce TEEs can join the ecosystem. In this case,
such a factory can get an intermediate CA certificate from one of the such a factory can get an intermediate CA certificate from one of the
existing roots without requiring that TAMs are updated with existing roots without requiring that TAMs are updated with
information about the new device factory. Likewise, new TAMs can information about the new device factory. Likewise, new TAMs can
join the ecosystem, providing they are issued a TAM certificate that join the ecosystem, providing they are issued a TAM certificate that
chains to an existing root whereby existing TEEs will be allowed to chains to an existing root whereby existing TEEs will be allowed to
be personalized by the TAM without requiring changes to the TEE be personalized by the TAM without requiring changes to the TEE
itself. This enables the ecosystem to scale, and avoids the need for itself. This enables the ecosystem to scale, and avoids the need for
centralized databases of all TEEs produced or all TAMs that exist. centralized databases of all TEEs produced or all TAMs that exist.
5.7. Message Security 5.8. Message Security
Messages created by a TAM are used to deliver device SD and TA Messages created by a TAM are used to deliver device SD and TA
management commands to a device, and device attestation and response management commands to a device, and device attestation and messages
messages created by the TEE to respond to TAM messages. created by the device TEE to respond to TAM messages.
These messages are signed end-to-end and are typically encrypted such These messages are signed end-to-end and are typically encrypted such
that only the targeted device TEE or TAM is able to decrypt and view that only the targeted device TEE or TAM is able to decrypt and view
the actual content. the actual content.
5.8. Security Domain Hierarchy and Ownership 5.9. Security Domain Hierarchy and Ownership
The primary job of a TAM is to help an SP to manage its trusted The primary job of a TAM is to help an SP to manage its trusted
applications. A TA is typically installed in an SD. An SD is applications. A TA is typically installed in an SD. An SD is
commonly created for an SP. commonly created for an SP.
When an SP delegates its SD and TA management to a TAM, an SD is When an SP delegates its SD and TA management to a TAM, an SD is
created on behalf of a TAM in a TEE and the owner of the SD is created on behalf of a TAM in a TEE and the owner of the SD is
assigned to the TAM. An SD may be associated with an SP but the TAM assigned to the TAM. An SD may be associated with an SP but the TAM
has full privilege to manage the SD for the SP. has full privilege to manage the SD for the SP.
Each SD for an SP is associated with only one TAM. When an SP Each SD for an SP is associated with only one TAM. When an SP
changes TAM, a new SP SD must be created to associate with the new changes TAM, a new SP SD must be created to associate with the new
TAM. The TEE will maintain a registry of TAM ID and SP SD ID TAM. The TEE will maintain a registry of TAM ID and SP SD ID
mapping. mapping.
From an SD ownership perspective, the SD tree is flat and there is From an SD ownership perspective, the SD tree is flat and there is
only one level. An SD is associated with its owner. It is up to TEE only one level. An SD is associated with its owner. It is up to the
implementation how it maintains SD binding information for a TAM and TEE implementation how it maintains SD binding information for a TAM
different SPs under the same TAM. and different SPs under the same TAM.
It is an important decision in this protocol specification that a TEE It is an important decision in this architecture that a TEE doesn't
doesn't need to know whether a TAM is authorized to manage the SD for need to know whether a TAM is authorized to manage the SD for an SP.
an SP. This authorization is implicitly triggered by an SP Client This authorization is implicitly triggered by an SP Client
Application, which instructs what TAM it wants to use. An SD is Application, which instructs what TAM it wants to use. An SD is
always associated with a TAM in addition to its SP ID. A rogue TAM always associated with a TAM in addition to its SP ID. A rogue TAM
isn't able to do anything on an unauthorized SP's SD managed by isn't able to do anything on an unauthorized SP's SD managed by
another TAM. another TAM.
Since a TAM may support multiple SPs, sharing the same SD name for Since a TAM may support multiple SPs, sharing the same SD name for
different SPs creates a dependency in deleting an SD. An SD can be different SPs creates a dependency in deleting an SD. An SD can be
deleted only after all TAs associated with this SD is deleted. An SP deleted only after all TAs associated with the SD are deleted. An SP
cannot delete a Security Domain on its own with a TAM if a TAM cannot delete a Security Domain on its own with a TAM if a TAM
decides to introduce such sharing. There are cases where multiple decides to introduce such sharing. There are cases where multiple
virtual SPs belong to the same organization, and a TAM chooses to use virtual SPs belong to the same organization, and a TAM chooses to use
the same SD name for those SPs. This is totally up to the TAM the same SD name for those SPs. This is totally up to the TAM
implementation and out of scope of this specification. implementation and out of scope of this specification.
5.9. SD Owner Identification and TAM Certificate Requirements 5.10. SD Owner Identification and TAM Certificate Requirements
There is a need of cryptographically binding proof about the owner of There is a need of cryptographically binding proof about the owner of
an SD in a device. When an SD is created on behalf of a TAM, a an SD in a device. When an SD is created on behalf of a TAM, a
future request from the TAM must present itself as a way that the TEE future request from the TAM must present itself as a way that the TEE
can verify it is the true owner. The certificate itself cannot can verify it is the true owner. The certificate itself cannot
reliably used as the owner because TAM may change its certificate. reliably used as the owner because TAM may change its certificate.
** need to handle the normal key roll-over case, as well as the less
frequent key compromise case
To this end, each TAM will be associated with a trusted identifier To this end, each TAM will be associated with a trusted identifier
defined as an attribute in the TAM certificate. This field is kept defined as an attribute in the TAM certificate. This field is kept
the same when the TAM renew its certificates. A TAM CA is the same when the TAM renew its certificates. A TAM CA is
responsible to vet the requested TAM attribute value. responsible to vet the requested TAM attribute value.
This identifier value must not collide among different TAM providers, This identifier value must not collide among different TAM providers,
and one TAM shouldn't be able to claim the identifier used by another and one TAM shouldn't be able to claim the identifier used by another
TAM provider. TAM provider.
The certificate extension name to carry the identifier can initially The certificate extension name to carry the identifier can initially
skipping to change at page 17, line 5 skipping to change at page 20, line 12
A CA can verify the domain ownership of the URL with the TAM in the A CA can verify the domain ownership of the URL with the TAM in the
certificate enrollment process. certificate enrollment process.
A TEE can assign this certificate attribute value as the TAM owner ID A TEE can assign this certificate attribute value as the TAM owner ID
for the SDs that are created for the TAM. for the SDs that are created for the TAM.
An alternative way to represent an SD ownership by a TAM is to have a An alternative way to represent an SD ownership by a TAM is to have a
unique secret key upon SD creation such that only the creator TAM is unique secret key upon SD creation such that only the creator TAM is
able to produce a proof-of-possession (PoP) data with the secret. able to produce a proof-of-possession (PoP) data with the secret.
5.10. Service Provider Container 5.11. Service Provider Container
A sample Security Domain hierarchy for the TEE is shown in Figure 4. A sample Security Domain hierarchy for the TEE is shown in Figure 6.
---------- ----------
| TEE | | TEE |
---------- ----------
| |
| ---------- | ----------
|----------| SP1 SD1 | |----------| SP1 SD1 |
| ---------- | ----------
| ---------- | ----------
|----------| SP1 SD2 | |----------| SP1 SD2 |
| ---------- | ----------
| ---------- | ----------
|----------| SP2 SD1 | |----------| SP2 SD1 |
---------- ----------
Figure 4: Security Domain Hiearchy Figure 6: Security Domain Hierarchy
The architecture separates SDs and TAs such that a TAM can only The architecture separates SDs and TAs such that a TAM can only
manage or retrieve data for SDs and TAs that it previously created manage or retrieve data for SDs and TAs that it previously created
for the SPs it represents. for the SPs it represents.
5.11. A Sample Device Setup Flow 5.12. A Sample Device Setup Flow
Step 1: Prepare Images for Devices Step 1: Prepare Images for Devices
1. [TEE vendor] Deliver TEE Image (CODE Binary) to device OEM -
2. [CA] Deliver root CA Whitelist 1. [TEE vendor] Deliver TEE Image (CODE Binary) to device OEM
3. [Soc] Deliver TFW Image -
1. [CA] Deliver root CA Whitelist
-
1. [Soc] Deliver TFW Image
Step 2: Inject Key Pairs and Images to Devices Step 2: Inject Key Pairs and Images to Devices
-
1. [OEM] Generate Secure Boot Key Pair (May be shared among multiple 1. [OEM] Generate TFW Key Pair (May be shared among multiple
devices) devices)
2. [OEM] Flash signed TFW Image and signed TEE Image onto devices -
(signed by Secure Boot Key)
Step 3: Setup attestation key pairs in devices 1. [OEM] Flash signed TFW Image and signed TEE Image onto devices
(signed by TFW Key)
1. [OEM] Flash Secure Boot Public Key and eFuse Key (eFuse key is Step 3: Set up attestation key pairs in devices
unique per device)
2. [TFW/TEE] Generate a unique attestation key pair and get a -
certificate for the device.
Step 4: Setup trust anchors in devices 1. [OEM] Flash TFW Public Key and a bootloader key.
1. [TFW/TEE] Store the key and certificate encrypted with the eFuse -
key
2. [TEE vendor or OEM] Store trusted CA certificate list into 1. [TFW/TEE] Generate a unique attestation key pair and get a
devices certificate for the device.
6. Agent Step 4: Set up trust anchors in devices
A TEE and TAs do not generally have capability to communicate to the -
outside of the hosting device. For example, the Global Platform
1. [TFW/TEE] Store the key and certificate encrypted with the
bootloader key
-
1. [TEE vendor or OEM] Store trusted CA certificate list into
devices
6. TEEP Broker
A TEE and TAs do not generally have the capability to communicate to
the outside of the hosting device. For example, GlobalPlatform
[GPTEE] specifies one such architecture. This calls for a software [GPTEE] specifies one such architecture. This calls for a software
module in the REE world to handle the network communication. Each module in the REE world to handle the network communication. Each
Client Application in REE may carry this communication functionality Client Application in the REE might carry this communication
but it must also interact with the TEE for the message exchange. The functionality but such functionality must also interact with the TEE
TEE interaction will vary according to different TEEs. In order for for the message exchange. The TEE interaction will vary according to
a Client Application to transparently support different TEEs, it is different TEEs. In order for a Client Application to transparently
imperative to have a common interface for a Client Application to support different TEEs, it is imperative to have a common interface
invoke for exchanging messages with TEEs. for a Client Application to invoke for exchanging messages with TEEs.
A shared agent comes to meed this need. An agent is an application A shared agent comes to meet this need. An agent is an application
running in the REE of the device or a SDK that facilitates running in the REE of the device or an SDK that facilitates
communication between a TAM and TEE. It also provides interfaces for communication between a TAM and a TEE. It also provides interfaces
TAM SDK or Client Applications to query and trigger TA installation for TAM SDK or Client Applications to query and trigger TA
that the application needs to use. installation that the application needs to use.
This interface for Client Applications may be commonly an Android This interface for Client Applications may be commonly an OS service
service call for an Android powered device. A Client Application call for an REE OS. A Client Application interacts with a TAM, and
interacts with a TAM, and turns around to pass messages received from turns around to pass messages received from TAM to agent.
TAM to agent.
In all cases, a Client Application needs to be able to identify an In all cases, a Client Application needs to be able to identify an
agent that it can use. agent that it can use.
6.1. Role of the Agent 6.1. Role of the Agent
An agent abstracts the message exchanges with the TEE in a device. An agent abstracts the message exchanges with the TEE in a device.
The input data is originated from a TAM that a Client Application The input data is originated from a TAM to which a Client Application
connects. A Client Application may also directly call Agent for some connects. A Client Application may also directly call an Agent for
TA query functions. some TA query functions.
The agent may internally process a request from TAM. At least, it The agent may internally process a message from a TAM. At least, it
needs to know where to route a message, e.g., TEE instance. It does needs to know where to route a message, e.g., TEE instance. It does
not need to process or verify message content. not need to process or verify message content.
The agent returns TEE / TFW generated response messages to the The agent returns TEE / TFW generated response messages to the
caller. The agent is not expected to handle any network connection caller. The agent is not expected to handle any network connection
with an application or TAM. with an application or TAM.
The agent only needs to return an agent error message if the TEE is The agent only needs to return an agent error message if the TEE is
not reachable for some reason. Other errors are represented as not reachable for some reason. Other errors are represented as
response messages returned from the TEE which will then be passed to response messages returned from the TEE which will then be passed to
the TAM. the TAM.
6.2. Agent Implementation Consideration 6.2. Agent Implementation Consideration
A Provider should consider methods of distribution, scope and A Provider should consider methods of distribution, scope and
concurrency on device and runtime options when implementing an agent. concurrency on devices and runtime options when implementing an
Several non-exhaustive options are discussed below. Providers are agent. Several non-exhaustive options are discussed below.
encouraged to take advantage of the latest communication and platform Providers are encouraged to take advantage of the latest
capabilities to offer the best user experience. communication and platform capabilities to offer the best user
experience.
6.2.1. Agent Distribution 6.2.1. Agent Distribution
The agent installation is commonly carried out at OEM time. A user The agent installation is commonly carried out at OEM time. A user
can dynamically download and install an agent on-demand. can dynamically download and install an agent on-demand.
It is important to ensure a legitimate agent is installed and used. It is important to ensure a legitimate agent is installed and used.
If an agent is compromised it may drop messages and thereby If an agent is compromised it may drop messages and thereby introduce
introducing a denial of service. a denial of service.
6.2.2. Number of Agents 6.2.2. Number of Agents
We anticipate only one shared agent instance in a device. The We anticipate only one shared agent instance in a device. The
device's TEE vendor will most probably supply one aent. device's TEE vendor will most probably supply one agent.
With one shared agent, the agent provider is responsible to allow With one shared agent, the agent provider is responsible to allow
multiple TAMs and TEE providers to achieve interoperability. With a multiple TAMs and TEE providers to achieve interoperability. With a
standard agent interface, TAM can implement its own SDK for its SP standard agent interface, each TAM can implement its own SDK for its
Client Applications to work with this agent. SP Client Applications to work with this agent.
Multiple independent agent providers can be used as long as they have Multiple independent agent providers can be used as long as they have
standard interface to a Client Application or TAM SDK. Only one standard interface to a Client Application or TAM SDK. Only one
agent is expected in a device. agent is expected in a device.
TAM providers are generally expected to provide SDK for SP TAM providers are generally expected to provide an SDK for SP
applications to interact with an agent for the TAM and TEE applications to interact with an agent for the TAM and TEE
interaction. interaction.
7. Attestation 7. Attestation
7.1. Attestation Hierarchy 7.1. Attestation Hierarchy
The attestation hierarchy and seed required for TAM protocol The attestation hierarchy and seed required for TAM protocol
operation must be built into the device at manufacture. Additional operation must be built into the device at manufacture. Additional
TEEs can be added post-manufacture using the scheme proposed, but it TEEs can be added post-manufacture using the scheme proposed, but it
is outside of the current scope of this document to detail that. is outside of the current scope of this document to detail that.
It should be noted that the attestation scheme described is based on It should be noted that the attestation scheme described is based on
signatures. The only encryption that takes place may be the use of a signatures. The only decryption that may take place is through the
so-called eFuse to release the SBM signing key and later during the use of a bootloader key.
protocol lifecycle management interchange with the TAM.
SBM attestation can be optional in TEEP architecture where the A boot module generated attestation can be optional where the
starting point of device attestion can be at TEE certfificates. TAM starting point of device attestation can be at TEE certificates. A
can define its policies on what kind of TEE it trusts if TFW TAM can define its policies on what kinds of TEE it trusts if TFW
attestation isn't included during the TEE attestation. attestation is not included during the TEE attestation.
7.1.1. Attestation Hierarchy Establishment: Manufacture 7.1.1. Attestation Hierarchy Establishment: Manufacture
During manufacture the following steps are required: During manufacture the following steps are required:
1. A device-specific TFW key pair and certificate are burnt into the 1. A device-specific TFW key pair and certificate are burnt into the
device, encrypted by eFuse. This key pair will be used for device. This key pair will be used for signing operations
signing operations performed by the SBM. performed by the boot module.
2. TEE images are loaded and include a TEE instance-specific key 2. TEE images are loaded and include a TEE instance-specific key
pair and certificate. The key pair and certificate are included pair and certificate. The key pair and certificate are included
in the image and covered by the code signing hash. in the image and covered by the code signing hash.
3. The process for TEE images is repeated for any subordinate TEEs, 3. The process for TEE images is repeated for any subordinate TEEs,
which are additional TEEs after the root TEE that some devices which are additional TEEs after the root TEE that some devices
have. have.
7.1.2. Attestation Hierarchy Establishment: Device Boot 7.1.2. Attestation Hierarchy Establishment: Device Boot
During device boot the following steps are required: During device boot the following steps are required:
1. Secure boot releases the TFW private key by decrypting it with 1. The boot module releases the TFW private key by decrypting it
eFuse. with the bootloader key.
2. The SBM verifies the code-signing signature of the active TEE and 2. The boot module verifies the code-signing signature of the active
places its TEE public key into a signing buffer, along with its TEE and places its TEE public key into a signing buffer, along
identifier for later access. For a TEE non-compliant to this with its identifier for later access. For a TEE non-compliant to
architecture, the SBM leaves the TEE public key field blank. this architecture, the boot module leaves the TEE public key
field blank.
3. The SBM signs the signing buffer with the TFW private key. 3. The boot module signs the signing buffer with the TFW private
key.
4. Each active TEE performs the same operation as the SBM, building 4. Each active TEE performs the same operation as the boot module,
up their own signed buffer containing subordinate TEE building up their own signed buffer containing subordinate TEE
information. information.
7.1.3. Attestation Hierarchy Establishment: TAM 7.1.3. Attestation Hierarchy Establishment: TAM
Before a TAM can begin operation in the marketplace to support Before a TAM can begin operation in the marketplace, it must obtain a
devices of a given TEE, it must obtain a TAM certificate from a CA TAM certificate from a CA that is registered in the trust store of
that is registered in the trust store of devices with that TEE. In devices. In this way, the TEE can check the intermediate and root CA
this way, the TEE can check the intermediate and root CA and verify and verify that it trusts this TAM to perform operations on the TEE.
that it trusts this TAM to perform operations on the TEE.
8. Acknowledgements 8. Algorithm and Attestation Agility
The authors thank Dave Thaler for his very thorough review and many RFC 7696 [RFC7696] outlines the requirements to migrate from one
important suggestions. Most content of this document are split from mandatory-to-implement algorithm suite to another over time. This
a previously combined OTrP protocol document feature is also known as crypto agility. Protocol evolution is
[I-D.ietf-teep-opentrustprotocol]. We thank the former co-authors greatly simplified when crypto agility is already considered during
Nick Cook and Minho Yoo for the initial document content, and the design of the protocol. In the case of Open Trust Protocol
contributors Brian Witten, Tyler Kim, and Alin Mutu. (OTrP) the diverse range of use cases, from trusted app updates for
smart phones and tablets to updates of code on higher-end IoT
devices, creates the need for different mandatory-to-implement
algorithms already from the start.
9. Security Consideration Crypto agility in the OTrP concerns the use of symmetric as well as
asymmetric algorithms. Symmetric algorithms are used for encryption
of content whereas the asymmetric algorithms are mostly used for
signing messages.
In addition to the use of cryptographic algorithms in OTrP there is
also the need to make use of different attestation technologies. A
Device must provide techniques to inform a TAM about the attestation
technology it supports. For many deployment cases it is more likely
for the TAM to support one or more attestation techniques whereas the
Device may only support one.
9. Security Considerations
9.1. TA Trust Check at TEE 9.1. TA Trust Check at TEE
A TA binary is signed by a TA signer certificate. This TA signing A TA binary is signed by a TA signer certificate. This TA signing
certificate/private key belongs to the SP, and may be self-signed certificate/private key belongs to the SP, and may be self-signed
(i.e., it need not participate in a trust hierarchy). It is the (i.e., it need not participate in a trust hierarchy). It is the
responsibility of the TAM to only allow verified TAs from trusted SPs responsibility of the TAM to only allow verified TAs from trusted SPs
into the system. Delivery of that TA to the TEE is then the into the system. Delivery of that TA to the TEE is then the
responsibility of the TEE, using the security mechanisms provided by responsibility of the TEE, using the security mechanisms provided by
the protocol. the protocol.
skipping to change at page 22, line 12 skipping to change at page 25, line 42
trust checks on the certificate returned for this TA. It might trust trust checks on the certificate returned for this TA. It might trust
the TAM, or require additional SP signer trust chaining. the TAM, or require additional SP signer trust chaining.
9.2. One TA Multiple SP Case 9.2. One TA Multiple SP Case
A TA for multiple SPs must have a different identifier per SP. A TA A TA for multiple SPs must have a different identifier per SP. A TA
will be installed in a different SD for each respective SP. will be installed in a different SD for each respective SP.
9.3. Agent Trust Model 9.3. Agent Trust Model
An agent could be malware in the vulnerable Rich OS. A Client An agent could be malware in the vulnerable REE. A Client
Application will connect its TAM provider for required TA Application will connect its TAM provider for required TA
installation. It gets command messages from the TAM, and passes the installation. It gets command messages from the TAM, and passes the
message to the agent. message to the agent.
The architecture enables the TAM to communicate with the device's TEE The architecture enables the TAM to communicate with the device's TEE
to manage SDs and TAs. All TAM messages are signed and sensitive to manage SDs and TAs. All TAM messages are signed and sensitive
data is encrypted such that the agent cannot modify or capture data is encrypted such that the agent cannot modify or capture
sensitive data. sensitive data.
9.4. Data Protection at TAM and TEE 9.4. Data Protection at TAM and TEE
The TEE implementation provides protection of data on the device. It The TEE implementation provides protection of data on the device. It
is the responsibility of the TAM to protect data on its servers. is the responsibility of the TAM to protect data on its servers.
9.5. Compromised CA 9.5. Compromised CA
A root CA for TAM certificates might get compromised. Some TEE trust A root CA for TAM certificates might get compromised. Some TEE trust
anchor update mechanism is expected from device OEM. A compromised anchor update mechanism is expected from device OEMs. A compromised
intermediate CA is covered by OCSP stapling and OCSP validation check intermediate CA is covered by OCSP stapling and OCSP validation check
in the protocol. A TEE should validate certificate revocation about in the protocol. A TEE should validate certificate revocation about
a TAM certificate chain. a TAM certificate chain.
If the root CA of some TEE device certificates is compromised, these If the root CA of some TEE device certificates is compromised, these
devices might be rejected by a TAM, which is a decision of the TAM devices might be rejected by a TAM, which is a decision of the TAM
implementation and policy choice. Any intermediate CA for TEE device implementation and policy choice. Any intermediate CA for TEE device
certificates SHOULD be validated by TAM with a Certificate Revocation certificates SHOULD be validated by TAM with a Certificate Revocation
List (CRL) or Online Certificate Status Protocol (OCSP) method. List (CRL) or Online Certificate Status Protocol (OCSP) method.
skipping to change at page 23, line 16 skipping to change at page 26, line 46
TFW and TEE device certificates are expected to be long lived, longer TFW and TEE device certificates are expected to be long lived, longer
than the lifetime of a device. A TAM certificate usually has a than the lifetime of a device. A TAM certificate usually has a
moderate lifetime of 2 to 5 years. A TAM should get renewed or moderate lifetime of 2 to 5 years. A TAM should get renewed or
rekeyed certificates. The root CA certificates for a TAM, which are rekeyed certificates. The root CA certificates for a TAM, which are
embedded into the trust anchor store in a device, should have long embedded into the trust anchor store in a device, should have long
lifetimes that don't require device trust anchor update. On the lifetimes that don't require device trust anchor update. On the
other hand, it is imperative that OEMs or device providers plan for other hand, it is imperative that OEMs or device providers plan for
support of trust anchor update in their shipped devices. support of trust anchor update in their shipped devices.
10. References 10. IANA Considerations
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate This document does not require actions by IANA.
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
editor.org/info/rfc2119>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 11. Acknowledgements
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web The authors thank Dave Thaler for his very thorough review and many
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May important suggestions. Most content of this document is split from a
2015, <https://www.rfc-editor.org/info/rfc7515>. previously combined OTrP protocol document
[I-D.ietf-teep-opentrustprotocol]. We thank the former co-authors
Nick Cook and Minho Yoo for the initial document content, and
contributors Brian Witten, Tyler Kim, and Alin Mutu.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", 12. References
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<https://www.rfc-editor.org/info/rfc7516>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517, 12.1. Normative References
DOI 10.17487/RFC7517, May 2015, <https://www.rfc-
editor.org/info/rfc7517>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
DOI 10.17487/RFC7518, May 2015, <https://www.rfc- Requirement Levels", BCP 14, RFC 2119,
editor.org/info/rfc7518>. DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
10.2. Informative References [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[GPTEE] Global Platform, "Global Platform, GlobalPlatform Device 12.2. Informative References
Technology: TEE System Architecture, v1.0", 2013.
[GPTEECLAPI] [GPTEE] Global Platform, "GlobalPlatform Device Technology: TEE
Global Platform, "Global Platform, GlobalPlatform Device System Architecture, v1.1", Global Platform GPD_SPE_009,
Technology: TEE Client API Specification, v1.0", 2013. January 2017, <https://globalplatform.org/specs-library/
tee-system-architecture-v1-1/>.
[I-D.ietf-teep-opentrustprotocol] [I-D.ietf-teep-opentrustprotocol]
Pei, M., Atyeo, A., Cook, N., Yoo, M., and H. Tschofenig, Pei, M., Atyeo, A., Cook, N., Yoo, M., and H. Tschofenig,
"The Open Trust Protocol (OTrP)", draft-ietf-teep- "The Open Trust Protocol (OTrP)", draft-ietf-teep-
opentrustprotocol-00 (work in progress), May 2018. opentrustprotocol-01 (work in progress), July 2018.
[RFC7696] Housley, R., "Guidelines for Cryptographic Algorithm
Agility and Selecting Mandatory-to-Implement Algorithms",
BCP 201, RFC 7696, DOI 10.17487/RFC7696, November 2015,
<https://www.rfc-editor.org/info/rfc7696>.
Appendix A. History
RFC EDITOR: PLEASE REMOVE THIS SECTION
IETF Drafts
draft-00: - Initial working group document
Authors' Addresses Authors' Addresses
Mingliang Pei Mingliang Pei
Symantec Symantec
350 Ellis St
Mountain View, CA 94043
USA
Email: mingliang_pei@symantec.com EMail: mingliang_pei@symantec.com
Hannes Tschofenig Hannes Tschofenig
Arm Ltd. Arm Limited
Absam, Tirol 6067
Austria
Email: Hannes.Tschofenig@arm.com EMail: hannes.tschofenig@arm.com
David Wheeler
Intel
EMail: david.m.wheeler@intel.com
Andrew Atyeo Andrew Atyeo
Intercede Intercede
St. Mary's Road, Lutterworth
Leicestershire, LE17 4PS
Great Britain
Email: andrew.atyeo@intercede.com EMail: andrew.atyeo@intercede.com
Dapeng Liu Dapeng
Alibaba Group Alibaba Group
Wangjing East Garden 4th Area,Chaoyang District
Beijing 100102
China
Email: maxpassion@gmail.com EMail: maxpassion@gmail.com
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