rfc9783.original   rfc9783.txt 
Network Working Group H. Tschofenig Independent Submission H. Tschofenig
Internet-Draft Request for Comments: 9783
Intended status: Informational S. Frost Category: Informational S. Frost
Expires: 27 March 2025 M. Brossard ISSN: 2070-1721 M. Brossard
Arm Limited Arm Limited
A. Shaw A. Shaw
HP Labs HP Labs
T. Fossati T. Fossati
Linaro Linaro
23 September 2024 May 2025
Arm's Platform Security Architecture (PSA) Attestation Token Arm's Platform Security Architecture (PSA) Attestation Token
draft-tschofenig-rats-psa-token-24
Abstract Abstract
The Arm Platform Security Architecture (PSA) is a family of hardware The Arm Platform Security Architecture (PSA) is a family of hardware
and firmware security specifications, as well as open-source and firmware security specifications, as well as open-source
reference implementations, to help device makers and chip reference implementations, to help device makers and chip
manufacturers build best-practice security into products. Devices manufacturers build best-practice security into products. Devices
that are PSA compliant can produce attestation tokens as described in that are PSA-compliant can produce attestation tokens as described in
this memo, which are the basis for many different protocols, this memo. Attestation tokens are the basis for many different
including secure provisioning and network access control. This protocols, including secure provisioning and network access control.
document specifies the PSA attestation token structure and semantics. This document specifies the PSA attestation token structure and
semantics.
The PSA attestation token is a profile of the Entity Attestation The PSA attestation token is a profile of the Entity Attestation
Token (EAT). This specification describes what claims are used in an Token (EAT). This specification describes what claims are used in an
attestation token generated by PSA compliant systems, how these attestation token generated by PSA compliant systems, how these
claims get serialized to the wire, and how they are cryptographically claims get serialized to the wire, and how they are cryptographically
protected. protected.
This informational document is published as an independent submission This Informational document is published as an Independent Submission
to improve interoperability with Arm's architecture. It is not a to improve interoperability with Arm's architecture. It is not a
standard nor a product of the IETF. standard nor a product of the IETF.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for informational purposes.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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 is a contribution to the RFC Series, independently of any other
and may be updated, replaced, or obsoleted by other documents at any RFC stream. The RFC Editor has chosen to publish this document at
time. It is inappropriate to use Internet-Drafts as reference its discretion and makes no statement about its value for
material or to cite them other than as "work in progress." implementation or deployment. Documents approved for publication by
the RFC Editor are not candidates for any level of Internet Standard;
see Section 2 of RFC 7841.
This Internet-Draft will expire on 27 March 2025. 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/rfc9783.
Copyright Notice Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4 2. Conventions and Definitions
3. PSA Attester Model . . . . . . . . . . . . . . . . . . . . . 5 3. PSA Attester Model
4. PSA Claims . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. PSA Claims
4.1. Caller Claims . . . . . . . . . . . . . . . . . . . . . . 8 4.1. Caller Claims
4.1.1. Nonce . . . . . . . . . . . . . . . . . . . . . . . . 8 4.1.1. Nonce
4.1.2. Client ID . . . . . . . . . . . . . . . . . . . . . . 9 4.1.2. Client ID
4.2. Target Identification Claims . . . . . . . . . . . . . . 9 4.2. Target Identification Claims
4.2.1. Instance ID . . . . . . . . . . . . . . . . . . . . 9 4.2.1. Instance ID
4.2.2. Implementation ID . . . . . . . . . . . . . . . . . . 10 4.2.2. Implementation ID
4.2.3. Certification Reference . . . . . . . . . . . . . . . 10 4.2.3. Certification Reference
4.3. Target State Claims . . . . . . . . . . . . . . . . . . . 11 4.3. Target State Claims
4.3.1. Security Lifecycle . . . . . . . . . . . . . . . . . 11 4.3.1. Security Lifecycle
4.3.2. Boot Seed . . . . . . . . . . . . . . . . . . . . . . 14 4.3.2. Boot Seed
4.4. Software Inventory Claims . . . . . . . . . . . . . . . . 14 4.4. Software Inventory Claims
4.4.1. Software Components . . . . . . . . . . . . . . . . . 14 4.4.1. Software Components
4.5. Verification Claims . . . . . . . . . . . . . . . . . . . 16 4.5. Verification Claims
4.5.1. Verification Service Indicator . . . . . . . . . . . 16 4.5.1. Verification Service Indicator
4.5.2. Profile Definition . . . . . . . . . . . . . . . . . 17 4.5.2. Profile Definition
4.6. Backwards Compatibility Considerations . . . . . . . . . 18 4.6. Backwards Compatibility Considerations
5. Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5. Profiles
5.1. Baseline Profile . . . . . . . . . . . . . . . . . . . . 20 5.1. Baseline Profile
5.1.1. Token Encoding and Signing . . . . . . . . . . . . . 20 5.1.1. Token Encoding and Signing
5.1.2. Freshness Model . . . . . . . . . . . . . . . . . . . 21 5.1.2. Freshness Model
5.1.3. Synopsis . . . . . . . . . . . . . . . . . . . . . . 21 5.1.3. Synopsis
5.2. Profile TFM . . . . . . . . . . . . . . . . . . . . . . . 22 5.2. Profile TFM
6. Collated CDDL . . . . . . . . . . . . . . . . . . . . . . . . 23 6. Collated CDDL
7. Scalability Considerations . . . . . . . . . . . . . . . . . 26 7. Scalability Considerations
8. PSA Token Verification . . . . . . . . . . . . . . . . . . . 27 8. PSA Token Verification
8.1. AR4SI Trustworthiness Claims Mappings . . . . . . . . . 28 8.1. AR4SI Trustworthiness Claims Mappings
8.2. Endorsements, Reference Values and Verification Key 8.2. Endorsements, Reference Values, and Verification Key
Material . . . . . . . . . . . . . . . . . . . . . . . . 29 Material
9. Implementation Status . . . . . . . . . . . . . . . . . . . . 29 9. Security and Privacy Considerations
10. Security and Privacy Considerations . . . . . . . . . . . . . 29 10. IANA Considerations
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 10.1. CBOR Web Token Claims Registration
11.1. CBOR Web Token Claims Registration . . . . . . . . . . . 30 10.1.1. Client ID Claim
11.1.1. Client ID Claim . . . . . . . . . . . . . . . . . . 30 10.1.2. Security Lifecycle Claim
11.1.2. Security Lifecycle Claim . . . . . . . . . . . . . 30 10.1.3. Implementation ID Claim
11.1.3. Implementation ID Claim . . . . . . . . . . . . . . 30 10.1.4. Certification Reference Claim
11.1.4. Certification Reference Claim . . . . . . . . . . . 31 10.1.5. Software Components Claim
11.1.5. Software Components Claim . . . . . . . . . . . . . 31 10.1.6. Verification Service Indicator Claim
11.1.6. Verification Service Indicator Claim . . . . . . . 31 10.2. Media Types
11.2. Media Types . . . . . . . . . . . . . . . . . . . . . . 32 10.3. CoAP Content-Formats Registration
11.3. CoAP Content-Formats Registration . . . . . . . . . . . 32 10.3.1. Registry Contents
11.3.1. Registry Contents . . . . . . . . . . . . . . . . . 32 11. References
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 11.1. Normative References
12.1. Normative References . . . . . . . . . . . . . . . . . . 33 11.2. Informative References
12.2. Informative References . . . . . . . . . . . . . . . . . 35 Appendix A. Examples
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 37 A.1. COSE Sign1 Token
A.1. COSE Sign1 Token . . . . . . . . . . . . . . . . . . . . 37 A.2. COSE Mac0 Token
A.2. COSE Mac0 Token . . . . . . . . . . . . . . . . . . . . . 39 Acknowledgments
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 41 Contributors
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Authors' Addresses
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 42
1. Introduction 1. Introduction
The Platform Security Architecture (PSA) [PSA] is a set of hardware The Platform Security Architecture (PSA) [PSA] is a set of hardware
and firmware specifications, backed by reference implementations and and firmware specifications backed by reference implementations and a
a security certification program [PSACertified]. The security security certification program [PSACertified]. The security
specifications have been published by Arm, while the certification specifications have been published by Arm, while the certification
program and reference implementations are the result of a program and reference implementations are the result of a
collaborative effort by companies from multiple sectors, including collaborative effort by companies from multiple sectors, including
evaluation laboratories, IP semiconductor vendors and security evaluation laboratories, IP semiconductor vendors, and security
consultancies. The main objective of the PSA initiative is to assist consultancies. The main objective of the PSA initiative is to assist
device manufacturers and chip makers in incorporating best-practice device manufacturers and chip makers in incorporating best-practice
security measures into their products. security measures into their products.
Many devices now have trusted execution environments that provide a Many devices now have Trusted Execution Environments (TEEs) that
safe space for security-sensitive code, such as cryptography, secure provide a safe space for security-sensitive code, such as
boot, secure storage, and other essential security functions. These cryptography, secure boot, secure storage, and other essential
security functions are typically exposed through a narrow and well- security functions. These security functions are typically exposed
defined interface, and can be used by operating system libraries and through a narrow and well-defined interface, and can be used by
applications. operating system libraries and applications.
As outlined in the RATS Architecture [RFC9334], an Attester produces As outlined in the Remote ATtestation procedureS (RATS) Architecture
a signed collection of Claims that constitutes Evidence about its [RFC9334], an Attester produces a signed collection of Claims that
target environment. This document focuses on the output provided by constitutes Evidence about its Target Environment. This document
PSA's Initial Attestation API [PSA-API]. This output corresponds to focuses on the output provided by PSA's Initial Attestation API
Evidence in [RFC9334] and, as a design decision, the PSA attestation [PSA-API]. This output corresponds to Evidence in [RFC9334] and, as
token is a profile of the Entity Attestation Token (EAT) [EAT]. Note a design decision, the PSA attestation token is a profile of the
that there are other profiles of EAT available, such as Entity Attestation Token (EAT) [EAT]. Note that there are other
[I-D.kdyxy-rats-tdx-eat-profile] and [I-D.mandyam-rats-qwestoken], profiles of EAT available for use with different use cases and by
for use with different use cases and by different attestation different attestation technologies, such as [RATS-TDX] and
technologies. [RATS-QWESTOKEN].
Since the PSA tokens are also consumed by services outside the Since the PSA tokens are also consumed by services outside the
device, there is an actual need to ensure interoperability. device, there is an actual need to ensure interoperability.
Interoperability needs are addressed here by describing the exact Interoperability needs are addressed here by describing the exact
syntax and semantics of the attestation claims, and defining the way syntax and semantics of the attestation claims, and defining the way
these claims are encoded and cryptographically protected. these claims are encoded and cryptographically protected.
Further details on concepts expressed below can be found in the PSA Further details on concepts expressed below can be found in the PSA
Security Model documentation [PSA-SM]. Security Model documentation [PSA-SM].
As mentioned in the abstract, this memo documents a vendor extension As mentioned in the abstract, this memo documents a vendor extension
to the RATS architecture, and is not a standard. to the RATS architecture and is not a standard.
2. Conventions and Definitions 2. Conventions and Definitions
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 "OPTIONAL" in this document are to be interpreted as described in BCP
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
The terms Attester, Relying Party, Verifier, Attestation Result, The terms Attester, Relying Party, Verifier, Attestation Result,
Target Environment, Attesting Environment and Evidence are defined in Target Environment, Attesting Environment, and Evidence are defined
[RFC9334]. We use the term "receiver" to refer to Relying Parties in [RFC9334]. We use the term "receiver" to refer to Relying Parties
and Verifiers. and Verifiers.
We use the terms Evidence, "PSA attestation token", and "PSA token" We use the terms Evidence, "PSA attestation token", and "PSA token"
interchangeably. The terms "sender" and Attester are used interchangeably. The terms "sender" and Attester are used
interchangeably. Likewise, we use the terms Verifier and interchangeably. Likewise, we use the terms Verifier and
"verification service" interchangeably. "verification service" interchangeably.
RoT: Root of Trust (RoT):
The minimal set of software, hardware, and data that has to be
Root of Trust, the minimal set of software, hardware and data that implicitly trusted in the platform; there is no software or
has to be implicitly trusted in the platform - there is no hardware at a deeper level that can verify that the RoT is
software or hardware at a deeper level that can verify that the authentic and unmodified. An example of RoT is an initial
Root of Trust is authentic and unmodified. An example of RoT is bootloader in ROM, which contains cryptographic functions and
an initial bootloader in ROM, which contains cryptographic credentials, running on a specific hardware platform.
functions and credentials, running on a specific hardware
platform.
SPE: Secure Processing Environment (SPE):
Secure Processing Environment, a platform's processing environment A platform's processing environment for software that provides
for software that provides confidentiality and integrity for its confidentiality and integrity for its runtime state, from software
runtime state, from software and hardware, outside of the SPE. and hardware, outside of the SPE. Contains trusted code and
Contains trusted code and trusted hardware. (Equivalent to trusted hardware. (Equivalent to a TEE, "secure world", or
Trusted Execution Environment (TEE), "secure world", or "secure "secure enclave".)
enclave".)
NSPE: Non-Secure Processing Environment (NSPE):
Non Secure Processing Environment, the security domain outside of The security domain outside of the SPE, the Application domain,
the SPE, the Application domain, typically containing the typically containing the application firmware, real-time operating
application firmware, real-time operating systems, applications systems, applications, and general hardware. (Equivalent to Rich
and general hardware. (Equivalent to Rich Execution Environment Execution Environment (REE), or "normal world".)
(REE), or "normal world".)
In this document, the structure of data is specified in Concise Data In this document, the structure of data is specified in Concise Data
Definition Language (CDDL) [RFC8610]. Definition Language (CDDL) [RFC8610].
3. PSA Attester Model 3. PSA Attester Model
Figure 1 outlines the structure of the PSA Attester according to the Figure 1 outlines the structure of the PSA Attester according to the
conceptual model described in Section 3.1 of [RFC9334]. conceptual model described in Section 3.1 of [RFC9334].
.----------. .----------.
skipping to change at page 6, line 45 skipping to change at line 251
Figure 1: PSA Attester Figure 1: PSA Attester
The PSA Attester is a relatively straightforward embodiment of the The PSA Attester is a relatively straightforward embodiment of the
RATS Attester with exactly one Attesting Environment and one or more RATS Attester with exactly one Attesting Environment and one or more
Target Environments. Target Environments.
The Attesting Environment is responsible for collecting the The Attesting Environment is responsible for collecting the
information to be represented in PSA claims and to assemble them into information to be represented in PSA claims and to assemble them into
Evidence. It is made of two cooperating components: Evidence. It is made of two cooperating components:
* The Main Bootloader, executing at boot-time, measures the Target * Executing at boot-time, the Main Bootloader measures the Target
Environments - i.e., loaded software components, and all the Environments (i.e., loaded software components and all the
relevant PSA RoT parameters -, and stores the recorded information relevant PSA RoT parameters) and stores the recorded information
in secure memory (Main Boot State). See Figure 2. in secure memory (Main Boot State). See Figure 2.
i-th Target Main Boot Main Boot i-th Target Main Boot Main Boot
Environment Loader State Environment Loader State
| | | | | |
.--------|-------------|-------------|----. .--------|-------------|-------------|----.
| loop i | | | | | loop i | | | |
| | measure | | | | | measure | | |
| |o------------+ | | | |o------------+ | |
| | | write | | | | | write | |
| | | measurement | | | | | measurement | |
| | +------------>| | | | +------------>| |
'--------|-------------|-------------|----' '--------|-------------|-------------|----'
| | | | | |
Figure 2: PSA Attester Boot Phase Figure 2: PSA Attester Boot Phase
* The Initial Attestation Service (executing at run-time in SPE) * The Initial Attestation Service (executing at run-time in SPE)
answers requests coming from NSPE via the PSA attestation API answers requests coming from NSPE via the PSA attestation API
[PSA-API], collects and formats the claims from Main Boot State, [PSA-API], collects and formats the claims from Main Boot State,
and uses the Initial Attestation Key (IAK) to sign them and and uses the Initial Attestation Key (IAK) to sign them and
produce Evidence. See Figure 3. produce Evidence. See Figure 3.
The word "Initial" in "Initial Attestation Service" refers to a The word "Initial" in "Initial Attestation Service" refers to a
limited set of Target Environments, namely those representing the limited set of Target Environments, namely those representing the
first, foundational stages establishing the chain of trust of a PSA first foundational stages establishing the chain of trust of a PSA
device. Collecting measurements from Target Environments after this device. Collecting measurements from Target Environments after this
initial phase is outside the scope of this specification. Extensions initial phase is outside the scope of this specification. Extensions
of this specification could collect up-to-date measurements from of this specification could collect up-to-date measurements from
additional Target Environments and define additional claims for use additional Target Environments and define additional claims for use
within those environments, but these are, by definition, custom. within those environments, but these are, by definition, custom.
Initial Initial
Main Boot Attestation Main Boot Attestation
State Service Verifier State Service Verifier
| | | | | |
skipping to change at page 8, line 4 skipping to change at line 303
| | i-th Target | | | | | i-th Target | | |
| | Environment | | | | | Environment | | |
| |<---------------+ | | | |<---------------+ | |
'--------|----------------|-----------|----' '--------|----------------|-----------|----'
| .---+ | | .---+ |
| sign | | | | sign | | |
| '-->| | | '-->| |
| | PSA Token | | | PSA Token |
| +---------->| | +---------->|
| | | | | |
Figure 3: PSA Attester Run-time Phase
Figure 3: PSA Attester Run-Time Phase
The Target Environments can be of four types, some of which may or The Target Environments can be of four types, some of which may or
may not be present depending on the device architecture: may not be present depending on the device architecture:
* (A subset of) the PSA RoT parameters, including Instance and * (A subset of) the PSA RoT parameters, including Instance and
Implementation IDs. Implementation IDs.
* The updateable PSA RoT, including the Secure Partition Manager and * The updateable PSA RoT, including the Secure Partition Manager and
all PSA RoT services. all PSA RoT services.
* The (optional) Application RoT, that is any application-defined * The (optional) Application RoT, that is any application-defined
security service, possibly making use of the PSA RoT services. security service possibly making use of the PSA RoT services.
* The loader of the application software running in NSPE. * The loader of the application software running in NSPE.
A reference implementation of the PSA Attester is provided by [TF-M]. A reference implementation of the PSA Attester is provided by [TF-M].
4. PSA Claims 4. PSA Claims
This section describes the claims to be used in a PSA attestation This section describes the claims to be used in a PSA attestation
token. A more comprehensive treatment of the EAT profile(s) defined token. A more comprehensive treatment of the EAT profiles defined by
by PSA is found in Section 5. PSA is found in Section 5.
CDDL [RFC8610] along with text descriptions is used to define each CDDL [RFC8610] along with text descriptions is used to define each
claim independent of encoding. The following CDDL type(s) are reused claim independent of encoding. The following CDDL types are reused
by different claims: by different claims:
psa-hash-type = bytes .size 32 / bytes .size 48 / bytes .size 64 psa-hash-type = bytes .size 32 / bytes .size 48 / bytes .size 64
Two conventions are used to encode the Right-Hand-Side (RHS) of a Two conventions are used to encode the Right-Hand-Side (RHS) of a
claim: the postfix -label is used for EAT-defined claims, and the claim. The postfix -label is used for EAT-defined claims and the
postfix -key for PSA-originated claims. postfix -key is used for PSA-originated claims.
4.1. Caller Claims 4.1. Caller Claims
4.1.1. Nonce 4.1.1. Nonce
The Nonce claim is used to carry the challenge provided by the caller The Nonce claim is used to carry the challenge provided by the caller
to demonstrate freshness of the generated token. to demonstrate freshness of the generated token.
The EAT [EAT] nonce (claim key 10) is used. Since the EAT nonce The EAT [EAT] nonce (claim key 10) is used. Since the EAT nonce
claim offers flexiblity for different attestation technologies, this claim offers flexiblity for different attestation technologies, this
specifications applies the following constraints to the nonce-type: specification applies the following constraints to the nonce-type:
* The length MUST be either 32, 48, or 64 bytes. * The length MUST be either 32, 48, or 64 bytes.
* Only a single nonce value is conveyed. The array notation MUST * Only a single nonce value is conveyed. The array notation MUST
NOT be used for encoding the nonce value. NOT be used for encoding the nonce value.
This claim MUST be present in a PSA attestation token. This claim MUST be present in a PSA attestation token.
psa-nonce = ( psa-nonce = (
nonce-label => psa-hash-type nonce-label => psa-hash-type
skipping to change at page 9, line 42 skipping to change at line 388
psa-client-id-spe-type = 1..2147483647 psa-client-id-spe-type = 1..2147483647
psa-client-id-type = psa-client-id-nspe-type / psa-client-id-spe-type psa-client-id-type = psa-client-id-nspe-type / psa-client-id-spe-type
psa-client-id = ( psa-client-id = (
psa-client-id-key => psa-client-id-type psa-client-id-key => psa-client-id-type
) )
4.2. Target Identification Claims 4.2. Target Identification Claims
4.2.1. Instance ID 4.2.1. Instance ID
The Instance ID claim represents the unique identifier of the Initial The Instance ID claim represents the unique identifier of the IAK.
Attestation Key (IAK). The full definition is in [PSA-SM]. The full definition is in [PSA-SM].
The EAT ueid (claim key 256) of type RAND is used. The following The EAT ueid (claim key 256) of type RAND is used. The following
constraints apply to the ueid-type: constraints apply to the ueid-type:
* The length MUST be 33 bytes. * The length MUST be 33 bytes.
* The first byte MUST be 0x01 (RAND) followed by the 32-byte unique * The first byte MUST be 0x01 (RAND) followed by the 32-byte unique
identifier of the IAK. [PSA-API] provides implementation options identifier of the IAK. [PSA-API] provides implementation options
for deriving the IAK unique identifier from the IAK itself. for deriving the IAK unique identifier from the IAK itself.
skipping to change at page 10, line 48 skipping to change at line 441
psa-implementation-id = ( psa-implementation-id = (
psa-implementation-id-key => psa-implementation-id-type psa-implementation-id-key => psa-implementation-id-type
) )
4.2.3. Certification Reference 4.2.3. Certification Reference
The Certification Reference claim is used to link the class of chip The Certification Reference claim is used to link the class of chip
and PSA RoT of the attesting device to an associated entry in the PSA and PSA RoT of the attesting device to an associated entry in the PSA
Certification database. It MUST be represented as a string made of Certification database. It MUST be represented as a string made of
nineteen numeric characters: a thirteen-digit [EAN-13], followed by a nineteen numeric characters: a thirteen-digit EAN-13 [EAN-13],
dash "-", followed by the five-digit versioning information described followed by a dash "-", and followed by the five-digit versioning
in [PSA-Cert-Guide]. information described in [PSA-Cert-Guide].
Linking to the PSA Certification entry can still be achieved if this Linking to the PSA Certification entry can still be achieved if this
claim is not present in the token by making an association at a claim is not present in the token by making an association at a
Verifier between the reference value and other token claim values - Verifier between the reference value and other token claim values,
for example, the Implementation ID. for example, the Implementation ID.
This claim MAY be present in a PSA attestation token. This claim MAY be present in a PSA attestation token.
psa-certification-reference-type = text .regexp "[0-9]{13}-[0-9]{5}" psa-certification-reference-type = text .regexp "[0-9]{13}-[0-9]{5}"
psa-certification-reference = ( psa-certification-reference = (
? psa-certification-reference-key => ? psa-certification-reference-key =>
psa-certification-reference-type psa-certification-reference-type
) )
skipping to change at page 14, line 38 skipping to change at line 597
The Software Components claim is a list of software components that The Software Components claim is a list of software components that
includes all the software (both code and configuration) loaded by the includes all the software (both code and configuration) loaded by the
PSA RoT. This claim MUST be included in attestation tokens produced PSA RoT. This claim MUST be included in attestation tokens produced
by an implementation conformant with [PSA-SM]. by an implementation conformant with [PSA-SM].
Each entry in the Software Components list describes one software Each entry in the Software Components list describes one software
component using the attributes described in the following component using the attributes described in the following
subsections. Unless explicitly stated, the presence of an attribute subsections. Unless explicitly stated, the presence of an attribute
is OPTIONAL. is OPTIONAL.
Note that, as described in [RFC9334], a relying party will typically Note that a Relying Party will typically see the result of the
see the result of the appraisal process from the Verifier in form of appraisal process from the Verifier in form of an Attestation Result
an Attestation Result, rather than the PSA token from the attesting rather than the PSA token from the attesting endpoint as described in
endpoint. Therefore, a relying party is not expected to understand [RFC9334]. Therefore, a Relying Party is not expected to understand
the Software Components claim. Instead, it is for the Verifier to the Software Components claim. Instead, it is for the Verifier to
check this claim against the available Reference Values and provide check this claim against the available Reference Values and provide
an answer in form of an "high level" Attestation Result, which may or an answer in form of a "high-level" Attestation Result, which may or
may not include the original Software Components claim. may not include the original Software Components claim.
psa-software-component = { psa-software-component = {
? &(measurement-type: 1) => text ? &(measurement-type: 1) => text
&(measurement-value: 2) => psa-hash-type &(measurement-value: 2) => psa-hash-type
? &(version: 4) => text ? &(version: 4) => text
&(signer-id: 5) => psa-hash-type &(signer-id: 5) => psa-hash-type
? &(measurement-desc: 6) => text ? &(measurement-desc: 6) => text
} }
skipping to change at page 15, line 24 skipping to change at line 625
psa-software-components-key => [ + psa-software-component ] psa-software-components-key => [ + psa-software-component ]
) )
4.4.1.1. Measurement Type 4.4.1.1. Measurement Type
The Measurement Type attribute (key=1) is a short string representing The Measurement Type attribute (key=1) is a short string representing
the role of this software component. the role of this software component.
The following measurement types MAY be used for code measurements: The following measurement types MAY be used for code measurements:
* "BL": a Boot Loader "BL": a Boot Loader
* "PRoT": a component of the PSA Root of Trust "PRoT": a component of the PSA Root of Trust
* "ARoT": a component of the Application Root of Trust "ARoT": a component of the Application Root of Trust
* "App": a component of the NSPE application "App": a component of the NSPE application
* "TS": a component of a Trusted Subsystem "TS": a component of a Trusted Subsystem
The same labels with a "_CONFIG" postfix (e.g., "PRoT_CONFIG") MAY be The same labels with a "_CONFIG" postfix (e.g., "PRoT_CONFIG") MAY be
used for configuration measurements. used for configuration measurements.
This attribute SHOULD be present in a PSA software component unless This attribute SHOULD be present in a PSA software component unless
there is a very good reason to leave it out - for example in networks there is a very good reason to leave it out, for example, in networks
with severely constrained bandwidth, where sparing a few bytes really with severely constrained bandwidth where sparing a few bytes really
makes a difference. makes a difference.
4.4.1.2. Measurement Value 4.4.1.2. Measurement Value
The Measurement Value attribute (key=2) represents a hash of the The Measurement Value attribute (key=2) represents a hash of the
invariant software component in memory at startup time. The value invariant software component in memory at startup time. The value
MUST be a cryptographic hash of 256 bits or stronger. MUST be a cryptographic hash of 256 bits or stronger.
This attribute MUST be present in a PSA software component. This attribute MUST be present in a PSA software component.
4.4.1.3. Version 4.4.1.3. Version
The Version attribute (key=4) is the issued software version in the The Version attribute (key=4) is the issued software version in the
skipping to change at page 16, line 29 skipping to change at line 675
This attribute MUST be present in a PSA software component to be This attribute MUST be present in a PSA software component to be
compliant with [PSA-SM]. compliant with [PSA-SM].
4.4.1.5. Measurement Description 4.4.1.5. Measurement Description
The Measurement Description attribute (key=6) contains a string The Measurement Description attribute (key=6) contains a string
identifying the hash algorithm used to compute the corresponding identifying the hash algorithm used to compute the corresponding
Measurement Value. The string SHOULD be encoded according to "Hash Measurement Value. The string SHOULD be encoded according to "Hash
Name String" in the "Named Information Hash Algorithm Registry" Name String" in the "Named Information Hash Algorithm Registry"
[IANA.named-information]. [NAMED-INFO].
4.5. Verification Claims 4.5. Verification Claims
The following claims are part of the PSA token (and therefore still The following claims are part of the PSA token (and are therefore
Evidence) but aim to help receivers, including relying parties, with still Evidence). However, they aim to help receivers, including
the processing of the received attestation Evidence. Relying Parties, with the processing of the received attestation
Evidence.
4.5.1. Verification Service Indicator 4.5.1. Verification Service Indicator
The Verification Service Indicator claim is a hint used by a relying The Verification Service Indicator claim is a hint used by a Relying
party to locate a verification service for the token. The value is a Party to locate a verification service for the token. The value is a
text string that can be used to locate the service (typically, a URL text string that can be used to locate the service (typically, a URL
specifying the address of the verification service API). A Relying specifying the address of the verification service API). A Relying
Party may choose to ignore this claim in favor of other information. Party may choose to ignore this claim in favor of other information.
psa-verification-service-indicator-type = text psa-verification-service-indicator-type = text
psa-verification-service-indicator = ( psa-verification-service-indicator = (
? psa-verification-service-indicator-key => ? psa-verification-service-indicator-key =>
psa-verification-service-indicator-type psa-verification-service-indicator-type
) )
It is assumed that the relying party is pre-configured with a list of
It is assumed that the Relying Party is pre-configured with a list of
trusted verification services and that the contents of this hint can trusted verification services and that the contents of this hint can
be used to look up the correct one. Under no circumstances must the be used to look up the correct one. Under no circumstances must the
relying party be tricked into contacting an unknown and untrusted Relying Party be tricked into contacting an unknown and untrusted
verification service since the returned Attestation Result cannot be verification service since the returned Attestation Result cannot be
relied on. relied on.
Note: This hint requires the relying party to parse the content of Note: This hint requires the Relying Party to parse the content of
the PSA token. Since the relying party may not be in possession of a the PSA token. Since the Relying Party may not be in possession of a
trust anchor to verify the digital signature, it uses the hint in the trust anchor to verify the digital signature, it uses the hint in the
same way as it would treat any other information provided by an same way as it would treat any other information provided by an
external party, which includes attacker-provided data. external party, which includes attacker-provided data.
4.5.2. Profile Definition 4.5.2. Profile Definition
The Profile Definition claim encodes the unique identifier that The Profile Definition claim encodes the unique identifier that
corresponds to the EAT profile described by this document. This corresponds to the EAT profile described by this document. This
allows a receiver to assign the intended semantics to the rest of the allows a receiver to assign the intended semantics to the rest of the
claims found in the token. claims found in the token.
The EAT eat_profile (claim key 265) is used. The EAT eat_profile (claim key 265) is used.
The URI encoding MUST be used. The URI encoding MUST be used.
The value MUST be tag:psacertified.org,2023:psa#tfm for the profile The value MUST be tag:psacertified.org,2023:psa#tfm for the profile
defined in Section 5.2. defined in Section 5.2.
Future profiles derived from the baseline PSA profile SHALL create Future profiles derived from the baseline PSA profile SHALL create
their unique value, as described in Section 4.5.2.1. their unique value as described in Section 4.5.2.1.
This claim MUST be present in a PSA attestation token. This claim MUST be present in a PSA attestation token.
See Section 4.6, for considerations about backwards compatibility See Section 4.6 for considerations about backwards compatibility with
with previous versions of the PSA attestation token format. previous versions of the PSA attestation token format.
psa-profile-type = "tag:psacertified.org,2023:psa#tfm" psa-profile-type = "tag:psacertified.org,2023:psa#tfm"
psa-profile = ( psa-profile = (
profile-label => psa-profile-type profile-label => psa-profile-type
) )
4.5.2.1. URI Structure for the Derived Profile Identifiers 4.5.2.1. URI Structure for the Derived Profile Identifiers
A new profile is associated with a unique string. A new profile is associated with a unique string.
The string MUST use the URI fragment syntax defined in Section 3.5 of The string MUST use the URI fragment syntax defined in Section 3.5 of
[RFC3986]. [RFC3986].
The string SHOULD be short to avoid unnecessary overhead. The string SHOULD be short to avoid unnecessary overhead.
To avoid collisions, profile authors SHOULD communicate upfront their To avoid collisions, profile authors SHOULD communicate their intent
intent to use a certain string using the enquiry form on the upfront to use a certain string that uses the inquiry form on the
[PSACertified] website. website [PSACertified].
To derive the value to be used for the eat_profile claim, the string To derive the value to be used for the eat_profile claim, the string
is added as a fragment to the tag:psacertified.org,2023:psa tag URI is added as a fragment to the tag:psacertified.org,2023:psa tag URI
[RFC4151]. [RFC4151].
For example, an hypothetical profile using only COSE_Mac0 with the For example, a hypothetical profile using only COSE_Mac0 with the AES
AES Message Authentication Code (AES-MAC) may decide to use the Message Authentication Code (AES-MAC) may decide to use the string
string "aes-mac". The eat_profile value would then be: "aes-mac". The eat_profile value would then be
tag:psacertified.org,2023:psa#aes-mac. tag:psacertified.org,2023:psa#aes-mac.
4.6. Backwards Compatibility Considerations 4.6. Backwards Compatibility Considerations
A previous version of this specification [PSA-OLD], identified by the An earlier draft of this document [PSA-OLD] identified by the
PSA_IOT_PROFILE_1 profile, used claim key values from the "private PSA_IOT_PROFILE_1 profile, used claim key values from the "private
use range" of the CWT Claims registry. These claim keys have now use range" of the CWT Claims registry. These claim keys have now
been deprecated. been deprecated.
Table 2 provides the mappings between the deprecated and new claim Table 2 provides the mappings between the deprecated and new claim
keys. keys.
+==============+=================+=================================+ +==============+=================+=================================+
| |PSA_IOT_PROFILE_1|tag:psacertified.org,2023:psa#tfm| | |PSA_IOT_PROFILE_1|tag:psacertified.org,2023:psa#tfm|
+==============+=================+=================================+ +==============+=================+=================================+
skipping to change at page 19, line 40 skipping to change at line 807
+--------------+-----------------+---------------------------------+ +--------------+-----------------+---------------------------------+
|Verification |-75010 |2400 | |Verification |-75010 |2400 |
|Service | | | |Service | | |
|Indicator | | | |Indicator | | |
+--------------+-----------------+---------------------------------+ +--------------+-----------------+---------------------------------+
Table 2: Claim Key Mappings Table 2: Claim Key Mappings
The new profile introduces three further changes: The new profile introduces three further changes:
* the "Boot Seed" claim is now optional and of variable length (see * The "Boot Seed" claim is now optional and of variable length (see
Section 4.3.2), Section 4.3.2).
* the "No Software Measurements" claim has been retired, * The "No Software Measurements" claim has been retired.
* the "Certification Reference" claim syntax changed from EAN-13 to * The "Certification Reference" claim syntax changed from EAN-13 to
EAN-13+5 (see Section 4.2.3). EAN-13+5 (see Section 4.2.3).
To simplify the transition to the token format described in this To simplify the transition to the token format described in this
document it is RECOMMENDED that Verifiers accept tokens encoded document, it is RECOMMENDED that Verifiers accept tokens encoded
according to the old profile (PSA_IOT_PROFILE_1) as well as to the according to the old profile (PSA_IOT_PROFILE_1) as well as to the
profile defined in this document (tag:psacertified.org,2023:psa#tfm), profile defined in this document (tag:psacertified.org,2023:psa#tfm),
at least for the time needed to their devices to upgrade. at least for the time needed to their devices to upgrade.
5. Profiles 5. Profiles
This document defines a baseline with common requirements that all This document defines a baseline with common requirements that all
PSA profiles must satisfy. (Note that this does not apply to PSA profiles must satisfy. (Note that this does not apply to
[PSA-OLD].) [PSA-OLD].)
This document also defines a "TFM" profile (Section 5.2) that builds This document also defines a "TFM" profile (Section 5.2) that builds
on the baseline while constraining the use of COSE algorithms to on the baseline while constraining the use of COSE algorithms to
improve interoperability between Attesters and Verifiers. improve interoperability between Attesters and Verifiers.
Baseline and TFM are what EAT calls a "partial" and "full" profile, Baseline and TFM are what the EAT calls a "partial" and "full"
respectively. See Section 6.2 of [EAT] for further details regarding profile, respectively. See Section 6.2 of [EAT] for further details
profiles. regarding profiles.
5.1. Baseline Profile 5.1. Baseline Profile
5.1.1. Token Encoding and Signing 5.1.1. Token Encoding and Signing
The PSA attestation token is encoded in CBOR [STD94] format. The The PSA attestation token is encoded in CBOR [STD94] format. The
CBOR representation of a PSA token MUST be "valid" according to the CBOR representation of a PSA token MUST be "valid" according to the
definition in Section 1.2 of [STD94]. Besides, only definite-length definition in Section 1.2 of RFC 8949 [STD94]. Besides, only
string, arrays, and maps are allowed. Given that a PSA Attester is definite-length string, arrays, and maps are allowed. Given that a
typically found in a constrained device, it MAY NOT emit CBOR PSA Attester is typically found in a constrained device, it MAY NOT
preferred serializations (Section 4.1 of [STD94]). Therefore, the emit CBOR preferred serializations (Section 4.1 of RFC 8949 [STD94]).
Verifier MUST be a variation-tolerant CBOR decoder. Therefore, the Verifier MUST be a variation-tolerant CBOR decoder.
Cryptographic protection is obtained by wrapping the psa-token Cryptographic protection is obtained by wrapping the psa-token
claims-set in a COSE Web Token (CWT) [RFC8392]. For asymmetric key claims-set in a COSE Web Token (CWT) [RFC8392]. For asymmetric key
algorithms, the signature structure MUST be a tagged (18) COSE_Sign1. algorithms, the signature structure MUST be a tagged (18) COSE_Sign1.
For symmetric key algorithms, the signature structure MUST be a For symmetric key algorithms, the signature structure MUST be a
tagged (17) COSE_Mac0. tagged (17) COSE_Mac0.
Acknowledging the variety of markets, regulations and use cases in Acknowledging the variety of markets, regulations, and use cases in
which the PSA attestation token can be used, the baseline profile which the PSA attestation token can be used, the baseline profile
does not impose any strong requirement on the cryptographic does not impose any strong requirement on the cryptographic
algorithms that need to be supported by Attesters and Verifiers. The algorithms that need to be supported by Attesters and Verifiers. The
flexibility provided by the COSE format should be sufficient to deal flexibility provided by the COSE format should be sufficient to deal
with the level of cryptographic agility needed to adapt to specific with the level of cryptographic agility needed to adapt to specific
use cases. It is RECOMMENDED that commonly adopted algorithms are use cases. It is RECOMMENDED that commonly adopted algorithms are
used, such as those discussed in [COSE-ALGS]. It is expected that used, such as those discussed in [COSE-ALGS]. It is expected that
receivers will accept a wider range of algorithms, while Attesters receivers will accept a wider range of algorithms while Attesters
would produce PSA tokens using only one such algorithm. would produce PSA tokens using only one such algorithm.
The CWT CBOR tag (61) is not used. An application that needs to The CWT CBOR tag (61) is not used. An application that needs to
exchange PSA attestation tokens can wrap the serialised COSE_Sign1 or exchange PSA attestation tokens can wrap the serialized COSE_Sign1 or
COSE_Mac0 in the media type defined in Section 11.2 or the CoAP COSE_Mac0 in the media type defined in Section 10.2 or the CoAP
Content-Format defined in Section 11.3. Content-Format defined in Section 10.3.
A PSA token is always directly signed by the PSA RoT. Therefore, a A PSA token is always directly signed by the PSA RoT. Therefore, a
PSA claims-set (Section 4) is never carried in a Detached EAT bundle PSA claims-set (Section 4) is never carried in a Detached EAT bundle
(Section 5 of [EAT]). (Section 5 of [EAT]).
5.1.2. Freshness Model 5.1.2. Freshness Model
The PSA token supports the freshness models for attestation Evidence The PSA token supports the freshness models for attestation Evidence
based on nonces and epoch handles (Section 10.2 and Section 10.3 of based on nonces and epoch handles (Section 10.2 and Section 10.3 of
[RFC9334]) using the nonce claim to convey the nonce or epoch handle [RFC9334]) using the nonce claim to convey the nonce or epoch handle
skipping to change at page 22, line 8 skipping to change at line 894
string between 8 and 64 octets. string between 8 and 64 octets.
5.1.3. Synopsis 5.1.3. Synopsis
Table 3 presents a concise view of the requirements described in the Table 3 presents a concise view of the requirements described in the
preceding sections. preceding sections.
+==================+=============================================+ +==================+=============================================+
| Issue | Profile Definition | | Issue | Profile Definition |
+==================+=============================================+ +==================+=============================================+
| CBOR/JSON | CBOR MUST be used | | CBOR/JSON | CBOR MUST be used. |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
| CBOR Encoding | Definite length maps and arrays MUST be | | CBOR Encoding | Definite length maps and arrays MUST be |
| | used | | | used. |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
| CBOR Encoding | Definite length strings MUST be used | | CBOR Encoding | Definite length strings MUST be used. |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
| CBOR | Variant serialization MAY be used | | CBOR | Variant serialization MAY be used. |
| Serialization | | | Serialization | |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
| COSE Protection | COSE_Sign1 and/or COSE_Mac0 MUST be used | | COSE Protection | COSE_Sign1 and/or COSE_Mac0 MUST be used. |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
| Algorithms | [COSE-ALGS] SHOULD be used | | Algorithms | [COSE-ALGS] SHOULD be used. |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
| Detached EAT | Detached EAT bundles MUST NOT be sent | | Detached EAT | Detached EAT bundles MUST NOT be sent. |
| Bundle Usage | | | Bundle Usage | |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
| Verification Key | Any identification method listed in | | Verification Key | Any identification method listed in |
| Identification | Appendix F.1 of [EAT] | | Identification | Appendix F.1 of [EAT]. |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
| Endorsements | See Section 8.2 | | Endorsements | See Section 8.2. |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
| Freshness | nonce or epoch ID based | | Freshness | Nonce or epoch ID-based. |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
| Claims | Those defined in Section 4. As per general | | Claims | Those defined in Section 4. As per general |
| | EAT rules, the receiver MUST NOT error out | | | EAT rules, the receiver MUST NOT error out |
| | on claims it does not understand. | | | on claims it does not understand. |
+------------------+---------------------------------------------+ +------------------+---------------------------------------------+
Table 3: Baseline Profile Table 3: Baseline Profile
5.2. Profile TFM 5.2. Profile TFM
This profile is appropriate for the code base implemented in [TF-M] The TFM profile is appropriate for the code base implemented in
and should apply for most derivative implementations. If an [TF-M] and should apply for most derivative implementations. If an
implementation changes the requirements described below then, to implementation changes the requirements described below, then a
ensure interoperability, a different profile value should be used different profile value should be used (Section 4.5.2.1) to ensure
(Section 4.5.2.1). This includes a restriction of the profile to a interoperability. This includes a restriction of the profile to a
subset of the COSE Protection scheme requirements. subset of the COSE Protection scheme requirements.
Table 4 presents a concise view of the requirements. Table 4 presents a concise view of the requirements.
The value of the eat_profile MUST be The value of the eat_profile MUST be
tag:psacertified.org,2023:psa#tfm. tag:psacertified.org,2023:psa#tfm.
+================+=============================================+ +================+==============================================+
| Issue | Profile Definition | | Issue | Profile Definition |
+================+=============================================+ +================+==============================================+
| CBOR/JSON | See Section 5.1 | | CBOR/JSON | See Section 5.1. |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
| CBOR Encoding | See Section 5.1 | | CBOR Encoding | See Section 5.1. |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
| CBOR Encoding | See Section 5.1 | | CBOR Encoding | See Section 5.1. |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
| CBOR | See Section 5.1 | | CBOR | See Section 5.1. |
| Serialization | | | Serialization | |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
| COSE | COSE_Sign1 or COSE_Mac0 MUST be used | | COSE | COSE_Sign1 or COSE_Mac0 MUST be used. |
| Protection | | | Protection | |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
| Algorithms | The receiver MUST accept ES256, ES384 and | | Algorithms | The receiver MUST accept ES256, ES384, and |
| | ES512 with COSE_Sign1 and HMAC256/256, | | | ES512 with COSE_Sign1 and HMAC256/256, |
| | HMAC384/384 and HMAC512/512 with COSE_Mac0; | | | HMAC384/384, and HMAC512/512 with COSE_Mac0; |
| | the sender MUST send one of these | | | the sender MUST send one of these. |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
| Detached EAT | See Section 5.1 | | Detached EAT | See Section 5.1. |
| Bundle Usage | | | Bundle Usage | |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
| Verification | Claim-Based Key Identification | | Verification | Claim-Based Key Identification |
| Key | (Appendix F.1.4 of [EAT]) using Instance ID | | Key | (Appendix F.1.4 of [EAT]) using Instance ID. |
| Identification | | | Identification | |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
| Endorsements | See Section 8.2 | | Endorsements | See Section 8.2. |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
| Freshness | See Section 5.1 | | Freshness | See Section 5.1. |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
| Claims | See Section 5.1 | | Claims | See Section 5.1. |
+----------------+---------------------------------------------+ +----------------+----------------------------------------------+
Table 4: TF-M Profile Table 4: TF-M Profile
6. Collated CDDL 6. Collated CDDL
psa-token = { psa-token = {
psa-nonce psa-nonce
psa-instance-id psa-instance-id
psa-verification-service-indicator psa-verification-service-indicator
psa-profile psa-profile
psa-implementation-id psa-implementation-id
psa-client-id psa-client-id
skipping to change at page 26, line 4 skipping to change at line 1082
? &(version: 4) => text ? &(version: 4) => text
&(signer-id: 5) => psa-hash-type &(signer-id: 5) => psa-hash-type
? &(measurement-desc: 6) => text ? &(measurement-desc: 6) => text
} }
psa-software-components = ( psa-software-components = (
psa-software-components-key => [ + psa-software-component ] psa-software-components-key => [ + psa-software-component ]
) )
psa-verification-service-indicator-type = text psa-verification-service-indicator-type = text
psa-verification-service-indicator = ( psa-verification-service-indicator = (
? psa-verification-service-indicator-key => ? psa-verification-service-indicator-key =>
psa-verification-service-indicator-type psa-verification-service-indicator-type
) )
7. Scalability Considerations 7. Scalability Considerations
IAKs (see Section 3) can be either raw public keys or certified IAKs (see Section 3) can be either raw public keys or certified
public keys. public keys.
Certified public keys require the manufacturer to run the Certified public keys require the manufacturer to run the
certification authority (CA) that issues X.509 certs for the IAKs. certification authority (CA) that issues X.509 certifications for the
(Note that operating a CA is a complex and expensive task that may be IAKs. (Note that operating a CA is a complex and expensive task that
unaffordable to certain manufacturers.) may be unaffordable to certain manufacturers.)
Using certified public keys offers better scalability properties when Using certified public keys offers better scalability properties when
compared to using raw public keys, namely: compared to using raw public keys, namely:
* storage requirements for the Verifier are minimised - the same * Storage requirements for the Verifier are minimized; the same
manufacturer's trust anchor is used for any number of devices, manufacturer's trust anchor is used for any number of devices.
* the provisioning model is simpler and more robust since there is * The provisioning model is simpler and more robust since there is
no need to notify the Verifier about each newly manufactured no need to notify the Verifier about each newly manufactured
device, device.
Furthermore, existing and well-understood revocation mechanisms can Furthermore, existing and well-understood revocation mechanisms can
be readily used. be readily used.
The IAK's X.509 cert can be inlined in the PSA token using the The IAK's X.509 certification can be inlined in the PSA token using
x5chain COSE header parameter [COSE-X509] at the cost of an increase the x5chain COSE header parameter [COSE-X509] at the cost of an
in the PSA token size. Section 4.4 of [TLS12-IoT] and Section 15 of increase in the PSA token size. Section 4.4 of [TLS12-IoT] and
[TLS13-IoT] provide guidance for profiling X.509 certs used in IoT Section 15 of [TLS13-IoT] provide guidance for profiling X.509
deployments. Note that the exact split between pre-provisioned and certifications used in IoT deployments. Note that the exact split
inlined certs may vary depending on the specific deployment. In that between pre-provisioned and inlined certifcations may vary depending
respect, x5chain is quite flexible: it can contain the end-entity on the specific deployment. In that respect, x5chain is quite
(EE) cert only, the EE and a partial chain, or the EE and the full flexible. It can contain the end entity (EE) certification only, the
chain up to the trust anchor (see Section 2 of [COSE-X509] for the EE and a partial chain, or the EE and the full chain up to the trust
details). Constraints around network bandwidth and computing anchor (see Section 2 of [COSE-X509] for the details). Constraints
resources available to endpoints, such as network buffers, may around network bandwidth and computing resources available to
dictate a reasonable split point. endpoints, such as network buffers, may dictate a reasonable split
point.
8. PSA Token Verification 8. PSA Token Verification
To verify the token, the primary need is to check correct encoding To verify the token, the primary need is to check correct encoding
and signing as detailed in Section 5.1.1. The key used for and signing as detailed in Section 5.1.1. The key used for
verification is either supplied to the Verifier by an authorized verification is either supplied to the Verifier by an authorized
Endorser along with the corresponding Attester's Instance ID or Endorser along with the corresponding Attester's Instance ID or
inlined in the token using the x5chain header parameter as described inlined in the token using the x5chain header parameter as described
in Section 7. If the IAK is a raw public key, the Instance ID claim in Section 7. If the IAK is a raw public key and the Instance ID
is used to assist in locating the key used to verify the signature claim is used to assist in locating the key used to verify the
covering the CWT token. If the IAK is a certified public key, X.509 signature covering the CWT token. If the IAK is a certified public
path construction and validation (Section 6 of [X509]) up to a key, X.509 path construction and validation (Section 6 of [X509]) up
trusted CA MUST be successful before the key is used to verify the to a trusted CA MUST be successful before the key is used to verify
token signature. This also includes revocation checking. the token signature. This also includes revocation checking.
In addition, the Verifier will typically operate a policy where In addition, the Verifier will typically operate a policy where
values of some of the claims in this profile can be compared to values of some of the claims in this profile can be compared to
reference values, registered with the Verifier for a given reference values, registered with the Verifier for a given
deployment, in order to confirm that the device is endorsed by the deployment, in order to confirm that the device is endorsed by the
manufacturer supply chain. The policy may require that the relevant manufacturer supply chain. The policy may require that the relevant
claims must have a match to a registered reference value. All claims claims must have a match to a registered reference value. All claims
may be worthy of additional appraisal. It is likely that most may be worthy of additional appraisal. It is likely that most
deployments would include a policy with appraisal for the following deployments would include a policy with appraisal for the following
claims: claims:
* Implementation ID - the value of the Implementation ID can be used * Implementation ID: The value of the Implementation ID can be used
to identify the verification requirements of the deployment. to identify the verification requirements of the deployment.
* Software Component, Measurement Value - this value can uniquely * Software Component, Measurement Value: This value can uniquely
identify a firmware release from the supply chain. In some cases, identify a firmware release from the supply chain. In some cases,
a Verifier may maintain a record for a series of firmware a Verifier may maintain a record for a series of firmware releases
releases, being patches to an original baseline release. A being patches to an original baseline release. A verification
verification policy may then allow this value to match any point policy may then allow this value to match any point on that
on that release sequence or expect some minimum level of maturity release sequence or expect some minimum level of maturity related
related to the sequence. to the sequence.
* Software Component, Signer ID - where present in a deployment, * Software Component, Signer ID: Where present in a deployment, this
this could allow a Verifier to operate a more general policy than could allow a Verifier to operate a more general policy than that
that for Measurement Value as above, by allowing a token to for Measurement Value as above by allowing a token to contain any
contain any firmware entries signed by a known Signer ID, without firmware entries signed by a known Signer ID without checking for
checking for a uniquely registered version. a uniquely registered version.
* Certification Reference - if present, this value could be used as * Certification Reference: If present, this value could be used as a
a hint to locate security certification information associated hint to locate security certification information associated with
with the attesting device. An example could be a reference to a the attesting device. An example could be a reference to a
[PSACertified] certificate. [PSACertified] certificate.
8.1. AR4SI Trustworthiness Claims Mappings 8.1. AR4SI Trustworthiness Claims Mappings
[RATS-AR4SI] defines an information model that Verifiers can employ [RATS-AR4SI] defines an information model that Verifiers can employ
to produce Attestation Results. AR4SI provides a set of standardized to produce Attestation Results. AR4SI provides a set of standardized
appraisal categories and tiers that greatly simplifies the task of appraisal categories and tiers that greatly simplifies the task of
writing Relying Party policies in multi-attester environments. writing Relying Party policies in Multi-Attester environments.
The contents of Table 5 are intended as guidance for implementing a The contents of Table 5 are intended as guidance for implementing a
PSA Verifier that computes its results using AR4SI. The table PSA Verifier that computes its results using AR4SI. The table
describes which PSA Evidence claims (if any) are related to which describes which PSA Evidence claims (if any) are related to which
AR4SI trustworthiness claim, and therefore what the Verifier must AR4SI trustworthiness claim, and therefore what the Verifier must
consider when deciding if and how to appraise a certain feature consider when deciding if and how to appraise a certain feature
associated with the PSA Attester. associated with the PSA Attester.
+===================+=============================================+ +===================+=========================================+
| Trustworthiness | Related PSA claims | | Trustworthiness | Related PSA claims |
| Vector claims | | | Vector claims | |
+===================+=============================================+ +===================+=========================================+
| configuration | Software Components (Section 4.4.1) | | configuration | Software Components (Section 4.4.1) |
+-------------------+---------------------------------------------+ +-------------------+-----------------------------------------+
| executables | ditto | | executables | ditto |
+-------------------+---------------------------------------------+ +-------------------+-----------------------------------------+
| file-system | N/A | | file-system | N/A |
+-------------------+---------------------------------------------+ +-------------------+-----------------------------------------+
| hardware | Implementation ID (Section 4.2.2) | | hardware | Implementation ID (Section 4.2.2) |
+-------------------+---------------------------------------------+ +-------------------+-----------------------------------------+
| instance-identity | Instance ID (Section 4.2.1). The Security | | instance-identity | Instance ID (Section 4.2.1). The |
| | Lifecycle (Section 4.3.1) can also impact | | | Security Lifecycle (Section 4.3.1) can |
| | the derived identity. | | | also impact the derived identity. |
+-------------------+---------------------------------------------+ +-------------------+-----------------------------------------+
| runtime-opaque | Indirectly derived from executables, | | runtime-opaque | Indirectly derived from executables, |
| | hardware, and instance-identity. The | | | hardware, and instance-identity. The |
| | Security Lifecycle (Section 4.3.1) can also | | | Security Lifecycle (Section 4.3.1) can |
| | be relevant: for example, any debug state | | | also be relevant, e.g., any debug state |
| | will expose otherwise protected memory. | | | will expose otherwise protected memory. |
+-------------------+---------------------------------------------+ +-------------------+-----------------------------------------+
| sourced-data | N/A | | sourced-data | N/A |
+-------------------+---------------------------------------------+ +-------------------+-----------------------------------------+
| storage-opaque | Indirectly derived from executables, | | storage-opaque | Indirectly derived from executables, |
| | hardware, and instance-identity. | | | hardware, and instance-identity. |
+-------------------+---------------------------------------------+ +-------------------+-----------------------------------------+
Table 5: AR4SI Claims mappings Table 5: AR4SI Claims mappings
This document does not prescribe what value must be chosen based on This document does not prescribe what value must be chosen based on
each possible situation: when assigning specific Trustworthiness each possible situation. When assigning specific Trustworthiness
Claim values, an implementation is expected to follow the algorithm Claim values, an implementation is expected to follow the algorithm
described in Section 2.3.3 of [RATS-AR4SI]. described in Section 2.3.3 of [RATS-AR4SI].
8.2. Endorsements, Reference Values and Verification Key Material 8.2. Endorsements, Reference Values, and Verification Key Material
[PSA-Endorsements] defines a protocol based on the [RATS-CoRIM] data [PSA-Endorsements] defines a protocol based on the [RATS-CoRIM] data
model that can be used to convey PSA Endorsements, Reference Values model that can be used to convey PSA Endorsements, Reference Values,
and verification key material to the Verifier. and verification key material to the Verifier.
9. Implementation Status 9. Security and Privacy Considerations
// RFC Editor: please remove this section before pubblication.
Implementations of this specification are provided by the Trusted
Firmware-M project [TF-M], [IAT-VERIFIER], the Veraison project
[Veraison], and the Xclaim [Xclaim] library. All four
implementations are released as open-source software.
10. Security and Privacy Considerations
This specification re-uses the EAT specification and therefore the This specification reuses the EAT specification and therefore the CWT
CWT specification. Hence, the security and privacy considerations of specification. Hence, the security and privacy considerations of
those specifications apply here as well. those specifications apply here as well.
Since CWTs offer different ways to protect the token, this Since CWTs offer different ways to protect the token, this
specification profiles those options and allows signatures using specification profiles those options and allows signatures using
public key cryptography as well as message authentication codes public key cryptography as well as message authentication codes
(MACs). COSE_Sign1 is used for digital signatures and COSE_Mac0 for (MACs). COSE_Sign1 is used for digital signatures and COSE_Mac0 for
MACs, as defined in the COSE specification [STD96]. Note, however, MACs as defined in the COSE specification [STD96]. Note, however,
that the use of MAC authentication is NOT RECOMMENDED due to the that the use of MAC authentication is NOT RECOMMENDED due to the
associated infrastructure costs for key management and protocol associated infrastructure costs for key management and protocol
complexities. complexities.
A PSA Attester MUST NOT provide Evidence to an untrusted challenger, A PSA Attester MUST NOT provide Evidence to an untrusted challenger,
as it may allow attackers to interpose and trick the Verifier into as it may allow attackers to interpose and trick the Verifier into
believing the attacker is a legitimate Attester. This is especially believing the attacker is a legitimate Attester. This is especially
relevant to protocols that use PSA attestation tokens to authenticate relevant to protocols that use PSA attestation tokens to authenticate
the attester to a relying party. the attester to a Relying Party.
Attestation tokens contain information that may be unique to a device
and therefore they may allow to single out an individual device for
tracking purposes. Deployments that have privacy requirements must
take appropriate measures to ensure that the token is only used to
provision anonymous/pseudonym keys.
11. IANA Considerations
11.1. CBOR Web Token Claims Registration
IANA is requested to make permanent the following claims that have
been assigned via early allocation in the "CBOR Web Token (CWT)
Claims" registry [IANA-CWT].
11.1.1. Client ID Claim
* Claim Name: psa-client-id
* Claim Description: PSA Client ID
* JWT Claim Name: N/A
* Claim Key: 2394
* Claim Value Type(s): signed integer
* Change Controller: Hannes Tschofenig
* Specification Document(s): Section 4.1.2 of RFCthis
11.1.2. Security Lifecycle Claim
* Claim Name: psa-security-lifecycle
* Claim Description: PSA Security Lifecycle
* JWT Claim Name: N/A
* Claim Key: 2395
* Claim Value Type(s): unsigned integer
* Change Controller: Hannes Tschofenig
* Specification Document(s): Section 4.3.1 of RFCthis
11.1.3. Implementation ID Claim
* Claim Name: psa-implementation-id
* Claim Description: PSA Implementation ID
* JWT Claim Name: N/A
* Claim Key: 2396
* Claim Value Type(s): byte string
* Change Controller: Hannes Tschofenig
* Specification Document(s): Section 4.2.2 of RFCthis
11.1.4. Certification Reference Claim
* Claim Name: psa-certification-reference
* Claim Description: PSA Certification Reference
* JWT Claim Name: N/A
* Claim Key: 2398
* Claim Value Type(s): text string
* Change Controller: Hannes Tschofenig
* Specification Document(s): Section 4.2.3 of RFCthis Attestation tokens contain information that may be unique to a
device. Therefore, they may allow to single out an individual device
for tracking purposes. Deployments that have privacy requirements
must take appropriate measures to ensure that the token is only used
to provision anonymous/pseudonym keys.
11.1.5. Software Components Claim 10. IANA Considerations
* Claim Name: psa-software-components 10.1. CBOR Web Token Claims Registration
* Claim Description: PSA Software Components IANA has registered the following claims in the "CBOR Web Token (CWT)
Claims" registry [CWT].
* JWT Claim Name: N/A 10.1.1. Client ID Claim
* Claim Key: 2399 Claim Name: psa-client-id
Claim Description: PSA Client ID
JWT Claim Name: N/A
Claim Key: 2394
Claim Value Type(s): signed integer
Change Controller: Hannes Tschofenig
Specification Document(s): Section 4.1.2 of RFC 9783
* Claim Value Type(s): array 10.1.2. Security Lifecycle Claim
* Change Controller: Hannes Tschofenig Claim Name: psa-security-lifecycle
Claim Description: PSA Security Lifecycle
JWT Claim Name: N/A
Claim Key: 2395
Claim Value Type(s): unsigned integer
Change Controller: Hannes Tschofenig
Specification Document(s): Section 4.3.1 of RFC 9783
* Specification Document(s): Section 4.4.1 of RFCthis 10.1.3. Implementation ID Claim
11.1.6. Verification Service Indicator Claim Claim Name: psa-implementation-id
Claim Description: PSA Implementation ID
JWT Claim Name: N/A
Claim Key: 2396
Claim Value Type(s): byte string
Change Controller: Hannes Tschofenig
Specification Document(s): Section 4.2.2 of RFC 9783
* Claim Name: psa-verification-service-indicator 10.1.4. Certification Reference Claim
* Claim Description: PSA Verification Service Indicator Claim Name: psa-certification-reference
Claim Description: PSA Certification Reference
JWT Claim Name: N/A
Claim Key: 2398
Claim Value Type(s): text string
Change Controller: Hannes Tschofenig
Specification Document(s): Section 4.2.3 of RFC 9783
* JWT Claim Name: N/A 10.1.5. Software Components Claim
* Claim Key: 2400 Claim Name: psa-software-components
* Claim Value Type(s): text string Claim Description: PSA Software Components
JWT Claim Name: N/A
Claim Key: 2399
Claim Value Type(s): array
Change Controller: Hannes Tschofenig
Specification Document(s): Section 4.4.1 of RFC 9783
* Change Controller: Hannes Tschofenig 10.1.6. Verification Service Indicator Claim
* Specification Document(s): Section 4.5.1 of RFCthis Claim Name: psa-verification-service-indicator
Claim Description: PSA Verification Service Indicator
JWT Claim Name: N/A
Claim Key: 2400
Claim Value Type(s): text string
Change Controller: Hannes Tschofenig
Specification Document(s): Section 4.5.1 of RFC 9783
11.2. Media Types 10.2. Media Types
No new media type registration is requested. To indicate that the This document does not register any new media types. To indicate
transmitted content is a PSA attestation token, applications can use that the transmitted content is a PSA attestation token, applications
the application/eat+cwt media type defined in [EAT-MEDIATYPES] with can use the application/eat+cwt media type defined in
the eat_profile parameter set to tag:psacertified.org,2023:psa#tfm [EAT-MEDIATYPES] with the eat_profile parameter set to
(or tag:psacertified.org,2019:psa#legacy if the token is encoded tag:psacertified.org,2023:psa#tfm (or
according to the old profile, see Section 4.6). tag:psacertified.org,2019:psa#legacy if the token is encoded
according to the old profile; see Section 4.6).
11.3. CoAP Content-Formats Registration 10.3. CoAP Content-Formats Registration
IANA is requested to register two CoAP Content-Format IDs in the IANA has registered two CoAP Content-Format IDs in the First Come
"CoAP Content-Formats" registry [IANA-CoAP-Content-Formats]: First Served range of the "CoAP Content-Formats" registry
[Content-Formats]:
* One for the application/eat+cwt media type with the eat_profile * One for the application/eat+cwt media type with the eat_profile
parameter equal to tag:psacertified.org,2023:psa#tfm parameter equal to tag:psacertified.org,2023:psa#tfm.
* Another for the application/eat+cwt media type with the * Another for the application/eat+cwt media type with the
eat_profile parameter equal to eat_profile parameter equal to
tag:psacertified.org,2019:psa#legacy tag:psacertified.org,2019:psa#legacy.
The Content-Formats should be allocated from the First Come First
Served range (10000-64999).
11.3.1. Registry Contents 10.3.1. Registry Contents
* Media Type: application/eat+cwt; Media Type: application/eat+cwt;
eat_profile="tag:psacertified.org,2023:psa#tfm" eat_profile="tag:psacertified.org,2023:psa#tfm"
Encoding: -
ID: 10003
Reference: RFC 9783
* Encoding: - Media Type: application/eat+cwt;
* Id: [[To-be-assigned by IANA]]
* Reference: RFCthis
* Media Type: application/eat+cwt;
eat_profile="tag:psacertified.org,2019:psa#legacy" eat_profile="tag:psacertified.org,2019:psa#legacy"
Encoding: -
ID: 10004
Reference: RFC 9783
* Encoding: - 11. References
* Id: [[To-be-assigned by IANA]]
* Reference: RFCthis
12. References
12.1. Normative References 11.1. Normative References
[COSE-ALGS] [COSE-ALGS]
Schaad, J., "CBOR Object Signing and Encryption (COSE): Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053, Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053,
August 2022, <https://www.rfc-editor.org/rfc/rfc9053>. August 2022, <https://www.rfc-editor.org/info/rfc9053>.
[EAN-13] GS1, "International Article Number - EAN/UPC barcodes", [CWT] IANA, "CBOR Web Token (CWT) Claims",
2019, <https://www.gs1.org/standards/barcodes/ean-upc>. <https://www.iana.org/assignments/cwt>.
[EAN-13] GS1, "EAN/UPC barcodes",
<https://www.gs1.org/standards/barcodes/ean-upc>.
[EAT] Lundblade, L., Mandyam, G., O'Donoghue, J., and C. [EAT] Lundblade, L., Mandyam, G., O'Donoghue, J., and C.
Wallace, "The Entity Attestation Token (EAT)", Work in Wallace, "The Entity Attestation Token (EAT)", RFC 9711,
Progress, Internet-Draft, draft-ietf-rats-eat-31, 6 DOI 10.17487/RFC9711, April 2025,
September 2024, <https://datatracker.ietf.org/doc/html/ <https://www.rfc-editor.org/info/rfc9711>.
draft-ietf-rats-eat-31>.
[EAT-MEDIATYPES] [EAT-MEDIATYPES]
Lundblade, L., Birkholz, H., and T. Fossati, "EAT Media Lundblade, L., Birkholz, H., and T. Fossati, "Entity
Types", Work in Progress, Internet-Draft, draft-ietf-rats- Attestation Token (EAT) Media Types", RFC 9782,
eat-media-type-09, 21 August 2024, DOI 10.17487/RFC9782, May 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-rats- <https://www.rfc-editor.org/info/rfc9782>.
eat-media-type-09>.
[IANA-CWT] IANA, "CBOR Web Token (CWT) Claims", 2022,
<https://www.iana.org/assignments/cwt/cwt.xhtml#claims-
registry>.
[IANA.named-information] [NAMED-INFO]
IANA, "Named Information", IANA, "Named Information Hash Algorithm Registry",
<https://www.iana.org/assignments/named-information>. <https://www.iana.org/assignments/named-information>.
[PSA-Cert-Guide] [PSA-Cert-Guide]
PSA Certified, "PSA Certified Level 2 Step by Step Guide PSA Certified, "PSA Certified Level 2 Step by Step Guide
Version 1.1", 2020, Version 1.1", April 2020,
<https://www.psacertified.org/app/uploads/2020/07/ <https://www.psacertified.org/app/uploads/2020/07/
JSADEN011-PSA_Certified_Level_2_Step-by-Step- JSADEN011-PSA_Certified_Level_2_Step-by-Step-
1.1-20200403.pdf>. 1.1-20200403.pdf>.
[PSA-FF] Arm, "Platform Security Architecture Firmware Framework [PSA-FF] Arm, "Arm PSA Firmware Framework 1.0",
1.0 (PSA-FF)", February 2019,
<https://developer.arm.com/documentation/den0063/a>. <https://developer.arm.com/documentation/den0063/a>.
[PSA-SM] Arm, "Platform Security Model 1.1", December 2021, [PSA-SM] Arm, "Platform Security Model 1.1", December 2021,
<https://www.psacertified.org/app/uploads/2021/12/ <https://www.psacertified.org/app/uploads/2021/12/
JSADEN014_PSA_Certified_SM_V1.1_BET0.pdf>. JSADEN014_PSA_Certified_SM_V1.1_BET0.pdf>.
[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/rfc/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005, RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/rfc/rfc3986>. <https://www.rfc-editor.org/info/rfc3986>.
[RFC4151] Kindberg, T. and S. Hawke, "The 'tag' URI Scheme", [RFC4151] Kindberg, T. and S. Hawke, "The 'tag' URI Scheme",
RFC 4151, DOI 10.17487/RFC4151, October 2005, RFC 4151, DOI 10.17487/RFC4151, October 2005,
<https://www.rfc-editor.org/rfc/rfc4151>. <https://www.rfc-editor.org/info/rfc4151>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, [RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/rfc/rfc8392>. May 2018, <https://www.rfc-editor.org/info/rfc8392>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/rfc/rfc8610>. June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[STD94] Bormann, C. and P. Hoffman, "Concise Binary Object [STD94] Internet Standard 94,
<https://www.rfc-editor.org/info/std94>.
At the time of writing, this STD comprises the following:
Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949, Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020, DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>. <https://www.rfc-editor.org/info/rfc8949>.
[STD96] Schaad, J., "CBOR Object Signing and Encryption (COSE): [STD96] Internet Standard 96,
<https://www.rfc-editor.org/info/std96>.
At the time of writing, this STD comprises the following:
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052, Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022, DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/rfc/rfc9052>. <https://www.rfc-editor.org/info/rfc9052>.
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Countersignatures", STD 96, RFC 9338,
DOI 10.17487/RFC9338, December 2022,
<https://www.rfc-editor.org/info/rfc9338>.
[X509] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [X509] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/rfc/rfc5280>. <https://www.rfc-editor.org/info/rfc5280>.
12.2. Informative References 11.2. Informative References
[Content-Formats]
IANA, "CoAP Content-Formats",
<https://www.iana.org/assignments/core-parameters>.
[COSE-X509] [COSE-X509]
Schaad, J., "CBOR Object Signing and Encryption (COSE): Schaad, J., "CBOR Object Signing and Encryption (COSE):
Header Parameters for Carrying and Referencing X.509 Header Parameters for Carrying and Referencing X.509
Certificates", RFC 9360, DOI 10.17487/RFC9360, February Certificates", RFC 9360, DOI 10.17487/RFC9360, February
2023, <https://www.rfc-editor.org/rfc/rfc9360>. 2023, <https://www.rfc-editor.org/info/rfc9360>.
[I-D.kdyxy-rats-tdx-eat-profile]
Kostal, G., Dittakavi, S., Yeluri, R., Xia, H., and J. Yu,
"EAT profile for Intel® Trust Domain Extensions (TDX)
attestation result", Work in Progress, Internet-Draft,
draft-kdyxy-rats-tdx-eat-profile-01, 23 April 2024,
<https://datatracker.ietf.org/doc/html/draft-kdyxy-rats-
tdx-eat-profile-01>.
[I-D.mandyam-rats-qwestoken]
Mandyam, G., Sekhar, V., and S. Mohammed, "The Qualcomm
Wireless Edge Services (QWES) Attestation Token", Work in
Progress, Internet-Draft, draft-mandyam-rats-qwestoken-00,
1 November 2019, <https://datatracker.ietf.org/doc/html/
draft-mandyam-rats-qwestoken-00>.
[IANA-CoAP-Content-Formats]
IANA, "CoAP Content-Formats", 2022,
<https://www.iana.org/assignments/core-parameters>.
[IAT-VERIFIER] [IAT-VERIFIER]
Linaro, "iat-verifier", 2023, Trusted Firmware, "iat-verifier", commit:
0b49b00195b7733d6fe74e8f42ed4d7b81242801, 18 August 2023,
<https://git.trustedfirmware.org/TF-M/tf-m-tools.git/tree/ <https://git.trustedfirmware.org/TF-M/tf-m-tools.git/tree/
iat-verifier>. iat-verifier>.
[PSA] Arm, "Platform Security Architecture Resources", 2022, [PSA] Arm, "Platform Security Architecture Resources",
<https://developer.arm.com/architectures/security- <https://developer.arm.com/architectures/security-
architectures/platform-security-architecture/ architectures/platform-security-architecture/
documentation>. documentation>.
[PSA-API] Arm, "PSA Attestation API 1.0.3", 2022, <https://arm- [PSA-API] Arm, "PSA Certified Attestation API 1.0", October 2022,
software.github.io/psa-api/attestation/1.0/IHI0085- <https://arm-software.github.io/psa-api/attestation/1.0/
PSA_Certified_Attestation_API-1.0.3.pdf>. IHI0085-PSA_Certified_Attestation_API-1.0.3.pdf>.
[PSA-Endorsements] [PSA-Endorsements]
Fossati, T., Deshpande, Y., and H. Birkholz, "Arm's Fossati, T., Deshpande, Y., and H. Birkholz, "A CoRIM
Platform Security Architecture (PSA) Attestation Verifier Profile for Arm's Platform Security Architecture (PSA)",
Endorsements", Work in Progress, Internet-Draft, draft- Work in Progress, Internet-Draft, draft-fdb-rats-psa-
fdb-rats-psa-endorsements-05, 30 August 2024, endorsements-06, 3 March 2025,
<https://datatracker.ietf.org/doc/html/draft-fdb-rats-psa- <https://datatracker.ietf.org/doc/html/draft-fdb-rats-psa-
endorsements-05>. endorsements-06>.
[PSA-OLD] Tschofenig, H., Frost, S., Brossard, M., Shaw, A. L., and [PSA-OLD] Tschofenig, H., Frost, S., Brossard, M., Shaw, A. L., and
T. Fossati, "Arm's Platform Security Architecture (PSA) T. Fossati, "Arm's Platform Security Architecture (PSA)
Attestation Token", Work in Progress, Internet-Draft, Attestation Token", Work in Progress, Internet-Draft,
draft-tschofenig-rats-psa-token-07, 1 February 2021, draft-tschofenig-rats-psa-token-08, 24 March 2021,
<https://datatracker.ietf.org/doc/html/draft-tschofenig- <https://datatracker.ietf.org/doc/html/draft-tschofenig-
rats-psa-token-07>. rats-psa-token-08>.
[PSACertified] [PSACertified]
PSA Certified, "PSA Certified IoT Security Framework", PSA Certified, "PSA Certified IoT Security Framework",
2022, <https://psacertified.org>. <https://psacertified.org>.
[RATS-AR4SI] [RATS-AR4SI]
Voit, E., Birkholz, H., Hardjono, T., Fossati, T., and V. Voit, E., Birkholz, H., Hardjono, T., Fossati, T., and V.
Scarlata, "Attestation Results for Secure Interactions", Scarlata, "Attestation Results for Secure Interactions",
Work in Progress, Internet-Draft, draft-ietf-rats-ar4si- Work in Progress, Internet-Draft, draft-ietf-rats-ar4si-
07, 2 September 2024, 08, 6 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-rats- <https://datatracker.ietf.org/doc/html/draft-ietf-rats-
ar4si-07>. ar4si-08>.
[RATS-CoRIM] [RATS-CoRIM]
Birkholz, H., Fossati, T., Deshpande, Y., Smith, N., and Birkholz, H., Fossati, T., Deshpande, Y., Smith, N., and
W. Pan, "Concise Reference Integrity Manifest", Work in W. Pan, "Concise Reference Integrity Manifest", Work in
Progress, Internet-Draft, draft-ietf-rats-corim-05, 8 July Progress, Internet-Draft, draft-ietf-rats-corim-07, 3
2024, <https://datatracker.ietf.org/doc/html/draft-ietf- March 2025, <https://datatracker.ietf.org/doc/html/draft-
rats-corim-05>. ietf-rats-corim-07>.
[RATS-QWESTOKEN]
Mandyam, G., Sekhar, V., and S. Mohammed, "The Qualcomm
Wireless Edge Services (QWES) Attestation Token", Work in
Progress, Internet-Draft, draft-mandyam-rats-qwestoken-00,
1 November 2019, <https://datatracker.ietf.org/doc/html/
draft-mandyam-rats-qwestoken-00>.
[RATS-TDX] Kostal, G., Dittakavi, S., Yeluri, R., Xia, H., and J. Yu,
"EAT profile for Intel(r) Trust Domain Extensions (TDX)
attestation result", Work in Progress, Internet-Draft,
draft-kdyxy-rats-tdx-eat-profile-02, 13 December 2024,
<https://datatracker.ietf.org/doc/html/draft-kdyxy-rats-
tdx-eat-profile-02>.
[RFC9334] Birkholz, H., Thaler, D., Richardson, M., Smith, N., and [RFC9334] Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
W. Pan, "Remote ATtestation procedureS (RATS) W. Pan, "Remote ATtestation procedureS (RATS)
Architecture", RFC 9334, DOI 10.17487/RFC9334, January Architecture", RFC 9334, DOI 10.17487/RFC9334, January
2023, <https://www.rfc-editor.org/rfc/rfc9334>. 2023, <https://www.rfc-editor.org/info/rfc9334>.
[TF-M] Linaro, "Trusted Firmware-M", 2022, [TF-M] Trusted Firmware, "Trusted Firmware-M",
<https://www.trustedfirmware.org/projects/tf-m/>. <https://www.trustedfirmware.org/projects/tf-m/>.
[TLS12-IoT] [TLS12-IoT]
Tschofenig, H., Ed. and T. Fossati, "Transport Layer Tschofenig, H., Ed. and T. Fossati, "Transport Layer
Security (TLS) / Datagram Transport Layer Security (DTLS) Security (TLS) / Datagram Transport Layer Security (DTLS)
Profiles for the Internet of Things", RFC 7925, Profiles for the Internet of Things", RFC 7925,
DOI 10.17487/RFC7925, July 2016, DOI 10.17487/RFC7925, July 2016,
<https://www.rfc-editor.org/rfc/rfc7925>. <https://www.rfc-editor.org/info/rfc7925>.
[TLS13-IoT] [TLS13-IoT]
Tschofenig, H., Fossati, T., and M. Richardson, "TLS/DTLS Tschofenig, H., Fossati, T., and M. Richardson, "TLS/DTLS
1.3 Profiles for the Internet of Things", Work in 1.3 Profiles for the Internet of Things", Work in
Progress, Internet-Draft, draft-ietf-uta-tls13-iot- Progress, Internet-Draft, draft-ietf-uta-tls13-iot-
profile-09, 3 March 2024, profile-14, 5 May 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-uta- <https://datatracker.ietf.org/doc/html/draft-ietf-uta-
tls13-iot-profile-09>. tls13-iot-profile-14>.
[Veraison] The Veraison Project, "Veraison psatoken package", 2022,
<https://github.com/veraison/psatoken>.
[Xclaim] Lundblade, L., "Xclaim", 2022,
<https://github.com/laurencelundblade/xclaim>.
Appendix A. Examples Appendix A. Examples
The following examples show PSA attestation tokens for an The following examples show PSA attestation tokens for an
hypothetical system comprising a single measured software component. hypothetical system comprising a single measured software component.
The attesting device is in a lifecycle state (Section 4.3.1) of The attesting device is in a lifecycle state (Section 4.3.1) of
SECURED. The attestation has been requested from a client residing SECURED. The attestation has been requested from a client residing
in the SPE. in the SPE.
The example in Appendix A.1 illustrates the case where the IAK is an The example in Appendix A.1 illustrates the case where the IAK is an
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0119095a1a7fffffff19095b19300019010978217461673a707361636572 0119095a1a7fffffff19095b19300019010978217461673a707361636572
7469666965642e6f72672c323032333a7073612374666d19010c48000000 7469666965642e6f72672c323032333a7073612374666d19010c48000000
000000000019095f81a30558200404040404040404040404040404040404 000000000019095f81a30558200404040404040404040404040404040404
040404040404040404040404040404025820030303030303030303030303 040404040404040404040404040404025820030303030303030303030303
0303030303030303030303030303030303030303016450526f545820cf88 0303030303030303030303030303030303030303016450526f545820cf88
d330e7a5366a95cf744a4dbf0d50304d405edd8b2530e243eddbd3177820 d330e7a5366a95cf744a4dbf0d50304d405edd8b2530e243eddbd3177820
Acknowledgments Acknowledgments
Thank you Carsten Bormann for help with the CDDL. Thanks to Nicholas Thank you Carsten Bormann for help with the CDDL. Thanks to Nicholas
Wood, Eliot Lear, Yaron Sheffer, Kathleen Moriarty and Ned Smith for Wood, Eliot Lear, Yaron Sheffer, Kathleen Moriarty, and Ned Smith for
ideas, comments and suggestions. ideas, comments, and suggestions.
Contributors Contributors
Laurence Lundblade Laurence Lundblade
Security Theory LLC Security Theory LLC
Email: lgl@securitytheory.com Email: lgl@securitytheory.com
Tamas Ban Tamas Ban
Arm Limited Arm Limited
Email: Tamas.Ban@arm.com Email: Tamas.Ban@arm.com
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