draft-ietf-rats-eat-04.txt   draft-ietf-rats-eat-05.txt 
RATS Working Group G. Mandyam RATS Working Group G. Mandyam
Internet-Draft Qualcomm Technologies Inc. Internet-Draft Qualcomm Technologies Inc.
Intended status: Standards Track L. Lundblade Intended status: Standards Track L. Lundblade
Expires: March 4, 2021 Security Theory LLC Expires: June 4, 2021 Security Theory LLC
M. Ballesteros M. Ballesteros
J. O'Donoghue J. O'Donoghue
Qualcomm Technologies Inc. Qualcomm Technologies Inc.
August 31, 2020 December 01, 2020
The Entity Attestation Token (EAT) The Entity Attestation Token (EAT)
draft-ietf-rats-eat-04 draft-ietf-rats-eat-05
Abstract Abstract
An Entity Attestation Token (EAT) provides a signed (attested) set of An Entity Attestation Token (EAT) provides a signed (attested) set of
claims that describe state and characteristics of an entity, claims that describe state and characteristics of an entity,
typically a device like a phone or an IoT device. These claims are typically a device like a phone or an IoT device. These claims are
used by a relying party to determine how much it wishes to trust the used by a relying party to determine how much it wishes to trust the
entity. entity.
An EAT is either a CWT or JWT with some attestation-oriented claims. An EAT is either a CWT or JWT with some attestation-oriented claims.
skipping to change at page 1, line 45 skipping to change at page 1, line 45
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on March 4, 2021. This Internet-Draft will expire on June 4, 2021.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. CDDL, CWT and JWT . . . . . . . . . . . . . . . . . . . . 4 1.1. CWT, JWT and UCCS . . . . . . . . . . . . . . . . . . . . 5
1.2. Entity Overview . . . . . . . . . . . . . . . . . . . . . 5 1.2. CDDL . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. EAT Operating Models . . . . . . . . . . . . . . . . . . 5 1.3. Entity Overview . . . . . . . . . . . . . . . . . . . . . 5
1.4. What is Not Standardized . . . . . . . . . . . . . . . . 6 1.4. EAT Operating Models . . . . . . . . . . . . . . . . . . 6
1.4.1. Transmission Protocol . . . . . . . . . . . . . . . . 6 1.5. What is Not Standardized . . . . . . . . . . . . . . . . 7
1.4.2. Signing Scheme . . . . . . . . . . . . . . . . . . . 7 1.5.1. Transmission Protocol . . . . . . . . . . . . . . . . 7
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.5.2. Signing Scheme . . . . . . . . . . . . . . . . . . . 8
3. The Claims . . . . . . . . . . . . . . . . . . . . . . . . . 8 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Token ID Claim (cti and jti) . . . . . . . . . . . . . . 8 3. The Claims . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2. Timestamp claim (iat) . . . . . . . . . . . . . . . . . . 9 3.1. Token ID Claim (cti and jti) . . . . . . . . . . . . . . 9
3.3. Nonce Claim (nonce) . . . . . . . . . . . . . . . . . . . 9 3.2. Timestamp claim (iat) . . . . . . . . . . . . . . . . . . 10
3.3.1. nonce CDDL . . . . . . . . . . . . . . . . . . . . . 9 3.3. Nonce Claim (nonce) . . . . . . . . . . . . . . . . . . . 10
3.4. Universal Entity ID Claim (ueid) . . . . . . . . . . . . 9 3.3.1. nonce CDDL . . . . . . . . . . . . . . . . . . . . . 10
3.4.1. ueid CDDL . . . . . . . . . . . . . . . . . . . . . . 12 3.4. Universal Entity ID Claim (ueid) . . . . . . . . . . . . 11
3.5. Origination Claim (origination) . . . . . . . . . . . . . 12 3.4.1. ueid CDDL . . . . . . . . . . . . . . . . . . . . . . 13
3.5.1. origination CDDL . . . . . . . . . . . . . . . . . . 12 3.5. Origination Claim (origination) . . . . . . . . . . . . . 13
3.6. OEM Identification by IEEE (oemid) . . . . . . . . . . . 12 3.5.1. origination CDDL . . . . . . . . . . . . . . . . . . 13
3.6.1. oemid CDDL . . . . . . . . . . . . . . . . . . . . . 13 3.6. OEM Identification by IEEE (oemid) . . . . . . . . . . . 14
3.7. The Security Level Claim (security-level) . . . . . . . . 13 3.6.1. oemid CDDL . . . . . . . . . . . . . . . . . . . . . 14
3.7.1. security-level CDDL . . . . . . . . . . . . . . . . . 14 3.7. Hardware Version Claims (hardware-version-claims) . . . . 14
3.8. Secure Boot and Debug Enable State Claims (boot-state) . 14 3.8. Software Description and Version . . . . . . . . . . . . 15
3.8.1. Secure Boot Enabled . . . . . . . . . . . . . . . . . 14 3.9. The Security Level Claim (security-level) . . . . . . . . 15
3.8.2. Debug Disabled . . . . . . . . . . . . . . . . . . . 15 3.9.1. security-level CDDL . . . . . . . . . . . . . . . . . 16
3.8.3. Debug Disabled Since Boot . . . . . . . . . . . . . . 15 3.10. Secure Boot Claim (secure-boot) . . . . . . . . . . . . . 16
3.8.4. Debug Permanent Disable . . . . . . . . . . . . . . . 15 3.10.1. secure-boot CDDL . . . . . . . . . . . . . . . . . . 16
3.8.5. Debug Full Permanent Disable . . . . . . . . . . . . 15 3.11. Debug Status Claim (debug-status) . . . . . . . . . . . . 16
3.8.6. boot-state CDDL . . . . . . . . . . . . . . . . . . . 15 3.11.1. Enabled . . . . . . . . . . . . . . . . . . . . . . 17
3.9. The Location Claim (location) . . . . . . . . . . . . . . 15 3.11.2. Disabled . . . . . . . . . . . . . . . . . . . . . . 17
3.9.1. location CDDL . . . . . . . . . . . . . . . . . . . . 16 3.11.3. Disabled Since Boot . . . . . . . . . . . . . . . . 18
3.10. The Age Claim (age) . . . . . . . . . . . . . . . . . . . 16 3.11.4. Disabled Permanently . . . . . . . . . . . . . . . . 18
3.10.1. age CDDL . . . . . . . . . . . . . . . . . . . . . . 16 3.11.5. Disabled Fully and Permanently . . . . . . . . . . . 18
3.11. The Uptime Claim (uptime) . . . . . . . . . . . . . . . . 16 3.11.6. debug-status CDDL . . . . . . . . . . . . . . . . . 18
3.11.1. uptime CDDL . . . . . . . . . . . . . . . . . . . . 16 3.12. Including Keys . . . . . . . . . . . . . . . . . . . . . 18
3.12. The Submods Part of a Token (submods) . . . . . . . . . . 17 3.13. The Location Claim (location) . . . . . . . . . . . . . . 19
3.12.1. Two Types of Submodules . . . . . . . . . . . . . . 17 3.13.1. location CDDL . . . . . . . . . . . . . . . . . . . 19
3.12.1.1. Non-token Submodules . . . . . . . . . . . . . . 17 3.14. The Uptime Claim (uptime) . . . . . . . . . . . . . . . . 20
3.12.1.2. Nested EATs . . . . . . . . . . . . . . . . . . 17 3.14.1. uptime CDDL . . . . . . . . . . . . . . . . . . . . 20
3.12.2. No Inheritance . . . . . . . . . . . . . . . . . . . 18 3.15. The Intended Use Claim (intended-use) . . . . . . . . . . 20
3.12.3. Security Levels . . . . . . . . . . . . . . . . . . 18 3.15.1. intended-use CDDL . . . . . . . . . . . . . . . . . 21
3.12.4. Submodule Names . . . . . . . . . . . . . . . . . . 18 3.16. The Submodules Part of a Token (submods) . . . . . . . . 21
3.12.5. submods CDDL . . . . . . . . . . . . . . . . . . . . 18 3.16.1. Two Types of Submodules . . . . . . . . . . . . . . 21
4. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.16.1.1. Non-token Submodules . . . . . . . . . . . . . . 21
4.1. Common CDDL Types . . . . . . . . . . . . . . . . . . . . 19 3.16.1.2. Nested EATs . . . . . . . . . . . . . . . . . . 22
4.2. CDDL for CWT-defined Claims . . . . . . . . . . . . . . . 19 3.16.1.3. Unsecured JWTs and UCCS Tokens as Submodules . . 23
4.3. JSON . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.16.2. No Inheritance . . . . . . . . . . . . . . . . . . . 23
4.3.1. JSON Labels . . . . . . . . . . . . . . . . . . . . . 19 3.16.3. Security Levels . . . . . . . . . . . . . . . . . . 23
4.3.2. JSON Interoperability . . . . . . . . . . . . . . . . 20 3.16.4. Submodule Names . . . . . . . . . . . . . . . . . . 24
4.4. CBOR . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.16.5. submods CDDL . . . . . . . . . . . . . . . . . . . . 24
4.4.1. CBOR Labels . . . . . . . . . . . . . . . . . . . . . 20 4. Endorsements and Verification Keys . . . . . . . . . . . . . 24
4.4.2. CBOR Interoperability . . . . . . . . . . . . . . . . 21 5. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.5. Collected CDDL . . . . . . . . . . . . . . . . . . . . . 22 5.1. Common CDDL Types . . . . . . . . . . . . . . . . . . . . 24
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 5.2. CDDL for CWT-defined Claims . . . . . . . . . . . . . . . 24
5.1. Reuse of CBOR Web Token (CWT) Claims Registry . . . . . . 23 5.3. JSON . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.1.1. Claims Registered by This Document . . . . . . . . . 23 5.3.1. JSON Labels . . . . . . . . . . . . . . . . . . . . . 25
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 24 5.3.2. JSON Interoperability . . . . . . . . . . . . . . . . 25
6.1. UEID Privacy Considerations . . . . . . . . . . . . . . . 24 5.4. CBOR . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7. Security Considerations . . . . . . . . . . . . . . . . . . . 25 5.4.1. CBOR Interoperability . . . . . . . . . . . . . . . . 25
7.1. Key Provisioning . . . . . . . . . . . . . . . . . . . . 25 5.5. Collected CDDL . . . . . . . . . . . . . . . . . . . . . 26
7.1.1. Transmission of Key Material . . . . . . . . . . . . 25 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
7.2. Transport Security . . . . . . . . . . . . . . . . . . . 25 6.1. Reuse of CBOR Web Token (CWT) Claims Registry . . . . . . 26
7.3. Multiple EAT Consumers . . . . . . . . . . . . . . . . . 26 6.2. Claim Characteristics . . . . . . . . . . . . . . . . . . 27
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 6.2.1. Interoperability and Relying Party Orientation . . . 27
8.1. Normative References . . . . . . . . . . . . . . . . . . 26 6.2.2. Operating System and Technology Neutral . . . . . . . 27
8.2. Informative References . . . . . . . . . . . . . . . . . 28 6.2.3. Security Level Neutral . . . . . . . . . . . . . . . 28
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 30 6.2.4. Reuse of Extant Data Formats . . . . . . . . . . . . 28
A.1. Very Simple EAT . . . . . . . . . . . . . . . . . . . . . 30 6.2.5. Proprietary Claims . . . . . . . . . . . . . . . . . 28
A.2. Example with Submodules, Nesting and Security Levels . . 30 6.3. Claims Registered by This Document . . . . . . . . . . . 28
Appendix B. UEID Design Rationale . . . . . . . . . . . . . . . 30 7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 29
B.1. Collision Probability . . . . . . . . . . . . . . . . . . 30 7.1. UEID Privacy Considerations . . . . . . . . . . . . . . . 29
B.2. No Use of UUID . . . . . . . . . . . . . . . . . . . . . 33 7.2. Location Privacy Considerations . . . . . . . . . . . . . 30
Appendix C. Changes from Previous Drafts . . . . . . . . . . . . 34 8. Security Considerations . . . . . . . . . . . . . . . . . . . 30
C.1. From draft-rats-eat-01 . . . . . . . . . . . . . . . . . 34 8.1. Key Provisioning . . . . . . . . . . . . . . . . . . . . 30
C.2. From draft-mandyam-rats-eat-00 . . . . . . . . . . . . . 34 8.1.1. Transmission of Key Material . . . . . . . . . . . . 30
C.3. From draft-ietf-rats-eat-01 . . . . . . . . . . . . . . . 34 8.2. Transport Security . . . . . . . . . . . . . . . . . . . 31
C.4. From draft-ietf-rats-eat-02 . . . . . . . . . . . . . . . 34 8.3. Multiple EAT Consumers . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 32
9.1. Normative References . . . . . . . . . . . . . . . . . . 32
9.2. Informative References . . . . . . . . . . . . . . . . . 34
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 36
A.1. Very Simple EAT . . . . . . . . . . . . . . . . . . . . . 36
A.2. Example with Submodules, Nesting and Security Levels . . 36
Appendix B. UEID Design Rationale . . . . . . . . . . . . . . . 36
B.1. Collision Probability . . . . . . . . . . . . . . . . . . 36
B.2. No Use of UUID . . . . . . . . . . . . . . . . . . . . . 38
Appendix C. Changes from Previous Drafts . . . . . . . . . . . . 39
C.1. From draft-rats-eat-01 . . . . . . . . . . . . . . . . . 39
C.2. From draft-mandyam-rats-eat-00 . . . . . . . . . . . . . 39
C.3. From draft-ietf-rats-eat-01 . . . . . . . . . . . . . . . 39
C.4. From draft-ietf-rats-eat-02 . . . . . . . . . . . . . . . 40
C.5. From draft-ietf-rats-eat-03 . . . . . . . . . . . . . . . 40
C.6. From draft-ietf-rats-eat-04 . . . . . . . . . . . . . . . 40
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction 1. Introduction
Remote device attestation is a fundamental service that allows a Remote device attestation is a fundamental service that allows a
remote device such as a mobile phone, an Internet-of-Things (IoT) remote device such as a mobile phone, an Internet-of-Things (IoT)
device, or other endpoint to prove itself to a relying party, a device, or other endpoint to prove itself to a relying party, a
server or a service. This allows the relying party to know some server or a service. This allows the relying party to know some
characteristics about the device and decide whether it trusts the characteristics about the device and decide whether it trusts the
device. device.
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limited to the following: limited to the following:
o Proof of the make and model of the device hardware (HW) o Proof of the make and model of the device hardware (HW)
o Proof of the make and model of the device processor, particularly o Proof of the make and model of the device processor, particularly
for security-oriented chips for security-oriented chips
o Measurement of the software (SW) running on the device o Measurement of the software (SW) running on the device
o Configuration and state of the device o Configuration and state of the device
o Environmental characteristics of the device such as its GPS o Environmental characteristics of the device such as its GPS
location location
1.1. CDDL, CWT and JWT TODO: mention use for Attestation Evidence and Results.
An EAT token is either a CWT as defined in [RFC8392] or a JWT as 1.1. CWT, JWT and UCCS
defined in [RFC7519]. This specification defines additional claims
for entity attestation. For flexibility and ease of imlpementation in a wide variety of
environments, EATs can be either CBOR [RFC7049] or JSON [ECMAScript]
format. This specification simultaneously describes both formats.
An EAT is either a CWT as defined in [RFC8392], a UCCS as defined in
[UCCS.Draft], or a JWT as defined in [RFC7519]. This specification
extends those specifications with additional claims for attestation.
The identification of a protocol element as an EAT, whether CBOR or
JSON format, follows the general conventions used by CWT, JWT and
UCCS. Largely this depends on the protocol carrying the EAT. In
some cases it may be by content type (e.g., MIME type). In other
cases it may be through use of CBOR tags. There is no fixed
mechanism across all use cases.
1.2. CDDL
This specification uses CDDL, [RFC8610], as the primary formalism to This specification uses CDDL, [RFC8610], as the primary formalism to
define each claim. The implementor then interprets the CDDL to come define each claim. The implementor then interprets the CDDL to come
to either the CBOR [RFC7049] or JSON [ECMAScript] representation. In to either the CBOR [RFC7049] or JSON [ECMAScript] representation. In
the case of JSON, Appendix E of [RFC8610] is followed. Additional the case of JSON, Appendix E of [RFC8610] is followed. Additional
rules are given in Section 4.3.2 of this document where Appendix E is rules are given in Section 5.3.2 of this document where Appendix E is
insufficient. (Note that this is not to define a general means to insufficient. (Note that this is not to define a general means to
translate between CBOR and JSON, but only to define enough such that translate between CBOR and JSON, but only to define enough such that
the claims defined in this document can be rendered unambiguously in the claims defined in this document can be rendered unambiguously in
JSON). JSON).
1.2. Entity Overview The CWT specification was authored before CDDL was available and did
not use it. This specification includes a CDDL definition of most of
what is described in [RFC8392].
1.3. Entity Overview
An "entity" can be any device or device subassembly ("submodule") An "entity" can be any device or device subassembly ("submodule")
that can generate its own attestation in the form of an EAT. The that can generate its own attestation in the form of an EAT. The
attestation should be cryptographically verifiable by the EAT attestation should be cryptographically verifiable by the EAT
consumer. An EAT at the device-level can be composed of several consumer. An EAT at the device-level can be composed of several
submodule EAT's. It is assumed that any entity that can create an submodule EAT's. It is assumed that any entity that can create an
EAT does so by means of a dedicated root-of-trust (RoT). EAT does so by means of a dedicated root-of-trust (RoT).
Modern devices such as a mobile phone have many different execution Modern devices such as a mobile phone have many different execution
environments operating with different security levels. For example, environments operating with different security levels. For example,
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runs an operating system (OS) that hosts a plethora of downloadable runs an operating system (OS) that hosts a plethora of downloadable
apps. It may also have a TEE (Trusted Execution Environment) that is apps. It may also have a TEE (Trusted Execution Environment) that is
distinct, isolated, and hosts security-oriented functionality like distinct, isolated, and hosts security-oriented functionality like
biometric authentication. Additionally, it may have an eSE (embedded biometric authentication. Additionally, it may have an eSE (embedded
Secure Element) - a high security chip with defenses against HW Secure Element) - a high security chip with defenses against HW
attacks that can serve as a RoT. This device attestation format attacks that can serve as a RoT. This device attestation format
allows the attested data to be tagged at a security level from which allows the attested data to be tagged at a security level from which
it originates. In general, any discrete execution environment that it originates. In general, any discrete execution environment that
has an identifiable security level can be considered an entity. has an identifiable security level can be considered an entity.
1.3. EAT Operating Models 1.4. EAT Operating Models
TODO: Rewrite (or eliminate) this section in light of the RATS
architecture draft.
At least the following three participants exist in all EAT operating At least the following three participants exist in all EAT operating
models. Some operating models have additional participants. models. Some operating models have additional participants.
The Entity. This is the phone, the IoT device, the sensor, the sub- The Entity. This is the phone, the IoT device, the sensor, the sub-
assembly or such that the attestation provides information about. assembly or such that the attestation provides information about.
The Manufacturer. The company that made the entity. This may be a The Manufacturer. The company that made the entity. This may be a
chip vendor, a circuit board module vendor or a vendor of finished chip vendor, a circuit board module vendor or a vendor of finished
consumer products. consumer products.
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operating models to generally facilitate deployment and to allow for operating models to generally facilitate deployment and to allow for
some special scenarios. One special scenario has a validation some special scenarios. One special scenario has a validation
service that is monetized, most likely by the manufacturer. In service that is monetized, most likely by the manufacturer. In
another, a privacy proxy service processes the EAT before it is another, a privacy proxy service processes the EAT before it is
transmitted to the relying party. In yet another, symmetric key transmitted to the relying party. In yet another, symmetric key
material is used for signing. In this case the manufacturer should material is used for signing. In this case the manufacturer should
perform the verification, because any release of the key material perform the verification, because any release of the key material
would enable a participant other than the entity to create valid would enable a participant other than the entity to create valid
signed EATs. signed EATs.
1.4. What is Not Standardized 1.5. What is Not Standardized
The following is not standardized for EAT, just the same they are not The following is not standardized for EAT, just the same they are not
standardized for CWT or JWT. standardized for CWT or JWT.
1.4.1. Transmission Protocol 1.5.1. Transmission Protocol
EATs may be transmitted by any protocol the same as CWTs and JWTs. EATs may be transmitted by any protocol the same as CWTs and JWTs.
For example, they might be added in extension fields of other For example, they might be added in extension fields of other
protocols, bundled into an HTTP header, or just transmitted as files. protocols, bundled into an HTTP header, or just transmitted as files.
This flexibility is intentional to allow broader adoption. This This flexibility is intentional to allow broader adoption. This
flexibility is possible because EAT's are self-secured with signing flexibility is possible because EAT's are self-secured with signing
(and possibly additionally with encryption and anti-replay). The (and possibly additionally with encryption and anti-replay). The
transmission protocol is not required to fulfill any additional transmission protocol is not required to fulfill any additional
security requirements. security requirements.
For certain devices, a direct connection may not exist between the For certain devices, a direct connection may not exist between the
EAT-producing device and the Relying Party. In such cases, the EAT EAT-producing device and the Relying Party. In such cases, the EAT
should be protected against malicious access. The use of COSE and should be protected against malicious access. The use of COSE and
JOSE allows for signing and encryption of the EAT. Therefore, even JOSE allows for signing and encryption of the EAT. Therefore, even
if the EAT is conveyed through intermediaries between the device and if the EAT is conveyed through intermediaries between the device and
Relying Party, such intermediaries cannot easily modify the EAT Relying Party, such intermediaries cannot easily modify the EAT
payload or alter the signature. payload or alter the signature.
1.4.2. Signing Scheme 1.5.2. Signing Scheme
The term "signing scheme" is used to refer to the system that The term "signing scheme" is used to refer to the system that
includes end-end process of establishing signing attestation key includes end-end process of establishing signing attestation key
material in the entity, signing the EAT, and verifying it. This material in the entity, signing the EAT, and verifying it. This
might involve key IDs and X.509 certificate chains or something might involve key IDs and X.509 certificate chains or something
similar but different. The term "signing algorithm" refers just to similar but different. The term "signing algorithm" refers just to
the algorithm ID in the COSE signing structure. No particular the algorithm ID in the COSE signing structure. No particular
signing algorithm or signing scheme is required by this standard. signing algorithm or signing scheme is required by this standard.
There are three main implementation issues driving this. First, There are three main implementation issues driving this. First,
skipping to change at page 8, line 7 skipping to change at page 8, line 46
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.
This document reuses terminology from JWT [RFC7519], COSE [RFC8152], This document reuses terminology from JWT [RFC7519], COSE [RFC8152],
and CWT [RFC8392]. and CWT [RFC8392].
Claim Name. The human-readable name used to identify a claim. Claim Name. The human-readable name used to identify a claim.
Claim Key. The CBOR map key or JSON name used to identify a claim. Claim Key. The CBOR map key or JSON name used to identify a claim.
Claim Value. The CBOR map or JSON object value representing the Claim Value. The value portion of the claim. A claim value can be
value of the claim. any CBOR data item or JSON value.
CWT Claims Set. The CBOR map or JSON object that contains the claims CWT Claims Set. The CBOR map or JSON object that contains the claims
conveyed by the CWT or JWT. conveyed by the CWT or JWT.
Attestation Key Material (AKM). The key material used to sign the Attestation Key Material (AKM). The key material used to sign the
EAT token. If it is done symmetrically with HMAC, then this is a EAT token. If it is done symmetrically with HMAC, then this is a
simple symmetric key. If it is done with ECC, such as an IEEE simple symmetric key. If it is done with ECC, such as an IEEE
DevID [IDevID], then this is the private part of the EC key pair. DevID [IDevID], then this is the private part of the EC key pair.
If ECDAA is used, (e.g., as used by Enhanced Privacy ID, i.e. If ECDAA is used, (e.g., as used by Enhanced Privacy ID, i.e.
EPID) then it is the key material needed for ECDAA. EPID) then it is the key material needed for ECDAA.
skipping to change at page 8, line 37 skipping to change at page 9, line 29
including those in the CWT [IANA.CWT.Claims] and JWT IANA including those in the CWT [IANA.CWT.Claims] and JWT IANA
[IANA.JWT.Claims] claims registries. [IANA.JWT.Claims] claims registries.
o All claims are optional o All claims are optional
o No claims are mandatory o No claims are mandatory
o All claims that are not understood by implementations MUST be o All claims that are not understood by implementations MUST be
ignored ignored
There are no default values or meanings assigned to absent claims
other than they are not reported. The reason for a claim's absence
may be the implementation not supporting the claim, an inability to
determine its value, or a preference to report in a different way
such as a proprietary claim.
CDDL along with text descriptions is used to define each claim CDDL along with text descriptions is used to define each claim
indepdent of encoding. Each claim is defined as a CDDL group (the indepdent of encoding. Each claim is defined as a CDDL group (the
group is a general aggregation and type definition feature of CDDL). group is a general aggregation and type definition feature of CDDL).
In the encoding section Section 4, the CDDL groups turn into CBOR map In the encoding section Section 5, the CDDL groups turn into CBOR map
entries and JSON name/value pairs. entries and JSON name/value pairs.
TODO: add paragraph here about use for Attestation Evidence and for
Results.
3.1. Token ID Claim (cti and jti) 3.1. Token ID Claim (cti and jti)
CWT defines the "cti" claim. JWT defines the "jti" claim. These are CWT defines the "cti" claim. JWT defines the "jti" claim. These are
equivalent to each other in EAT and carry a unique token identifier equivalent to each other in EAT and carry a unique token identifier
as they do in JWT and CWT. They may be used to defend against re use as they do in JWT and CWT. They may be used to defend against re use
of the token but are distinct from the nonce that is used by the of the token but are distinct from the nonce that is used by the
relying party to guarantee freshness and defend against replay. relying party to guarantee freshness and defend against replay.
3.2. Timestamp claim (iat) 3.2. Timestamp claim (iat)
The "iat" claim defined in CWT and JWT is used to indicate the date- The "iat" claim defined in CWT and JWT is used to indicate the date-
of-creation of the token. of-creation of the token, the time at which the claims are collected
and the token is composed and signed.
The data for some claims may be held or cached for some period of
time before the token is created. This period may be long, even
days. Examples are measurements taken at boot or a geographic
position fix taken the last time a satellite signal was received.
There are individual timestamps associated with these claims to
indicate their age is older than the "iat" timestamp.
CWT allows the use floating-point for this claim. EAT disallows the
use of floating-point. No token may contain an iat claim in float-
point format. Any recipient of a token with a floating-point format
iat claim may consider it an error. A 64-bit integer representation
of epoch time can represent a range of +/- 500 billion years, so the
only point of a floating-point timestamp is to have precession
greater than one second. This is not needed for EAT.
3.3. Nonce Claim (nonce) 3.3. Nonce Claim (nonce)
All EATs should have a nonce to prevent replay attacks. The nonce is All EATs should have a nonce to prevent replay attacks. The nonce is
generated by the relying party, the end consumer of the token. It is generated by the relying party, the end consumer of the token. It is
conveyed to the entity over whatever transport is in use before the conveyed to the entity over whatever transport is in use before the
token is generated and then included in the token as the nonce claim. token is generated and then included in the token as the nonce claim.
This documents the nonce claim for registration in the IANA CWT This documents the nonce claim for registration in the IANA CWT
claims registry. This is equivalent to the JWT nonce claim that is claims registry. This is equivalent to the JWT nonce claim that is
skipping to change at page 9, line 32 skipping to change at page 10, line 48
be secure. A maximum of 64 bytes is set to limit the memory a be secure. A maximum of 64 bytes is set to limit the memory a
constrained implementation uses. This size range is not set for the constrained implementation uses. This size range is not set for the
already-registered JWT nonce, but it should follow this size already-registered JWT nonce, but it should follow this size
recommendation when used in an EAT. recommendation when used in an EAT.
Multiple nonces are allowed to accommodate multistage verification Multiple nonces are allowed to accommodate multistage verification
and consumption. and consumption.
3.3.1. nonce CDDL 3.3.1. nonce CDDL
nonce-type = [ + bstr .size (8..64) ] {::include cddl/nonce.cddl}
nonce-claim = (
nonce => nonce-type
)
3.4. Universal Entity ID Claim (ueid) 3.4. Universal Entity ID Claim (ueid)
UEID's identify individual manufactured entities / devices such as a UEID's identify individual manufactured entities / devices such as a
mobile phone, a water meter, a Bluetooth speaker or a networked mobile phone, a water meter, a Bluetooth speaker or a networked
security camera. It may identify the entire device or a submodule or security camera. It may identify the entire device or a submodule or
subsystem. It does not identify types, models or classes of devices. subsystem. It does not identify types, models or classes of devices.
It is akin to a serial number, though it does not have to be It is akin to a serial number, though it does not have to be
sequential. sequential.
UEID's must be universally and globally unique across manufacturers UEID's must be universally and globally unique across manufacturers
and countries. UEIDs must also be unique across protocols and and countries. UEIDs must also be unique across protocols and
systems, as tokens are intended to be embedded in many different systems, as tokens are intended to be embedded in many different
protocols and systems. No two products anywhere, even in completely protocols and systems. No two products anywhere, even in completely
different industries made by two different manufacturers in two different industries made by two different manufacturers in two
different countries should have the same UEID (if they are not global different countries should have the same UEID (if they are not global
and universal in this way, then relying parties receiving them will and universal in this way, then relying parties receiving them will
have to track other characteristics of the device to keep devices have to track other characteristics of the device to keep devices
distinct between manufacturers). distinct between manufacturers).
There are privacy considerations for UEID's. See Section 6.1. There are privacy considerations for UEID's. See Section 7.1.
The UEID should be permanent. It should never change for a given The UEID should be permanent. It should never change for a given
device / entity. In addition, it should not be reprogrammable. device / entity. In addition, it should not be reprogrammable.
UEID's are variable length. All implementations MUST be able to UEID's are variable length. All implementations MUST be able to
receive UEID's that are 33 bytes long (1 type byte and 256 bits). receive UEID's that are 33 bytes long (1 type byte and 256 bits).
The recommended maximum sent is also 33 bytes. The recommended maximum sent is also 33 bytes.
When the entity constructs the UEID, the first byte is a type and the When the entity constructs the UEID, the first byte is a type and the
following bytes the ID for that type. Several types are allowed to following bytes the ID for that type. Several types are allowed to
accommodate different industries and different manufacturing accommodate different industries and different manufacturing
skipping to change at page 11, line 31 skipping to change at page 12, line 31
| | | different registered company identifiers, and some | | | | different registered company identifiers, and some |
| | | unique per-device identifier. EUIs are often the | | | | unique per-device identifier. EUIs are often the |
| | | same as or similar to MAC addresses. This type | | | | same as or similar to MAC addresses. This type |
| | | includes MAC-48, an obsolete name for EUI-48. (Note | | | | includes MAC-48, an obsolete name for EUI-48. (Note |
| | | that while devices with multiple network interfaces | | | | that while devices with multiple network interfaces |
| | | may have multiple MAC addresses, there is only one | | | | may have multiple MAC addresses, there is only one |
| | | UEID for a device) [IEEE.802-2001], [OUI.Guide] | | | | UEID for a device) [IEEE.802-2001], [OUI.Guide] |
| 0x03 | IMEI | This is a 14-digit identifier consisting of an | | 0x03 | IMEI | This is a 14-digit identifier consisting of an |
| | | 8-digit Type Allocation Code and a 6-digit serial | | | | 8-digit Type Allocation Code and a 6-digit serial |
| | | number allocated by the manufacturer, which SHALL | | | | number allocated by the manufacturer, which SHALL |
| | | be encoded as a binary integer over 48 bits. The | | | | be encoded as byte string of length 14 with each |
| | | IMEI value encoded SHALL NOT include Luhn checksum | | | | byte as the digit's value (not the ASCII encoding |
| | | or SVN information. [ThreeGPP.IMEI] | | | | of the digit; the digit 3 encodes as 0x03, not |
| | | 0x33). The IMEI value encoded SHALL NOT include |
| | | Luhn checksum or SVN information. [ThreeGPP.IMEI] |
+------+------+-----------------------------------------------------+ +------+------+-----------------------------------------------------+
Table 1: UEID Composition Types Table 1: UEID Composition Types
UEID's are not designed for direct use by humans (e.g., printing on UEID's are not designed for direct use by humans (e.g., printing on
the case of a device), so no textual representation is defined. the case of a device), so no textual representation is defined.
The consumer (the relying party) of a UEID MUST treat a UEID as a The consumer (the relying party) of a UEID MUST treat a UEID as a
completely opaque string of bytes and not make any use of its completely opaque string of bytes and not make any use of its
internal structure. For example, they should not use the OUI part of internal structure. For example, they should not use the OUI part of
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scheme. scheme.
o Device manufacturers are allowed to change from one type of UEID o Device manufacturers are allowed to change from one type of UEID
to another anytime they want. For example, they may find they can to another anytime they want. For example, they may find they can
optimize their manufacturing by switching from type 0x01 to type optimize their manufacturing by switching from type 0x01 to type
0x02 or vice versa. The main requirement on the manufacturer is 0x02 or vice versa. The main requirement on the manufacturer is
that UEIDs be universally unique. that UEIDs be universally unique.
3.4.1. ueid CDDL 3.4.1. ueid CDDL
ueid-claim = ( {::include cddl/ueid.cddl}
ueid => bstr .size (7..33)
)
3.5. Origination Claim (origination) 3.5. Origination Claim (origination)
TODO: this claim is likely to be dropped in favor of Endorsement
identifier and locators.
This claim describes the parts of the device or entity that are This claim describes the parts of the device or entity that are
creating the EAT. Often it will be tied back to the device or chip creating the EAT. Often it will be tied back to the device or chip
manufacturer. The following table gives some examples: manufacturer. The following table gives some examples:
+-------------------+-----------------------------------------------+ +-------------------+-----------------------------------------------+
| Name | Description | | Name | Description |
+-------------------+-----------------------------------------------+ +-------------------+-----------------------------------------------+
| Acme-TEE | The EATs are generated in the TEE authored | | Acme-TEE | The EATs are generated in the TEE authored |
| | and configured by "Acme" | | | and configured by "Acme" |
| Acme-TPM | The EATs are generated in a TPM manufactured | | Acme-TPM | The EATs are generated in a TPM manufactured |
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+-------------------+-----------------------------------------------+ +-------------------+-----------------------------------------------+
TODO: consider a more structure approach where the name and the URI TODO: consider a more structure approach where the name and the URI
and other are in separate fields. and other are in separate fields.
TODO: This needs refinement. It is somewhat parallel to issuer claim TODO: This needs refinement. It is somewhat parallel to issuer claim
in CWT in that it describes the authority that created the token. in CWT in that it describes the authority that created the token.
3.5.1. origination CDDL 3.5.1. origination CDDL
origination-claim = ( {::include cddl/origination.cddl}
origination => string-or-uri
)
3.6. OEM Identification by IEEE (oemid) 3.6. OEM Identification by IEEE (oemid)
The IEEE operates a global registry for MAC addresses and company The IEEE operates a global registry for MAC addresses and company
IDs. This claim uses that database to identify OEMs. The contents IDs. This claim uses that database to identify OEMs. The contents
of the claim may be either an IEEE MA-L, MA-M, MA-S or an IEEE CID of the claim may be either an IEEE MA-L, MA-M, MA-S or an IEEE CID
[IEEE.RA]. An MA-L, formerly known as an OUI, is a 24-bit value used [IEEE.RA]. An MA-L, formerly known as an OUI, is a 24-bit value used
as the first half of a MAC address. MA-M similarly is a 28-bit value as the first half of a MAC address. MA-M similarly is a 28-bit value
uses as the first part of a MAC address, and MA-S, formerly known as uses as the first part of a MAC address, and MA-S, formerly known as
OUI-36, a 36-bit value. Many companies already have purchased one of OUI-36, a 36-bit value. Many companies already have purchased one of
these. A CID is also a 24-bit value from the same space as an MA-L, these. A CID is also a 24-bit value from the same space as an MA-L,
but not for use as a MAC address. IEEE has published Guidelines for but not for use as a MAC address. IEEE has published Guidelines for
Use of EUI, OUI, and CID [OUI.Guide] and provides a lookup services Use of EUI, OUI, and CID [OUI.Guide] and provides a lookup services
[OUI.Lookup] [OUI.Lookup]
Companies that have more than one of these IDs or MAC address blocks Companies that have more than one of these IDs or MAC address blocks
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Commonly, these are expressed in Hexadecimal Representation Commonly, these are expressed in Hexadecimal Representation
[IEEE.802-2001] also called the Canonical format. When this claim is [IEEE.802-2001] also called the Canonical format. When this claim is
encoded the order of bytes in the bstr are the same as the order in encoded the order of bytes in the bstr are the same as the order in
the Hexadecimal Representation. For example, an MA-L like "AC-DE-48" the Hexadecimal Representation. For example, an MA-L like "AC-DE-48"
would be encoded in 3 bytes with values 0xAC, 0xDE, 0x48. For JSON would be encoded in 3 bytes with values 0xAC, 0xDE, 0x48. For JSON
encoded tokens, this is further base64url encoded. encoded tokens, this is further base64url encoded.
3.6.1. oemid CDDL 3.6.1. oemid CDDL
oemid-claim = ( {::include cddl/oemid.cddl}
oemid => bstr
)
3.7. The Security Level Claim (security-level) 3.7. Hardware Version Claims (hardware-version-claims)
EATs have a claim that roughly characterizes the device / entities The hardware version can be claimed at three different levels, the
ability to defend against attacks aimed at capturing the signing key, chip, the circuit board and the final device assembly. An EAT can
forging claims and at forging EATs. This is done by roughly defining include any combination these claims.
four security levels as described below. This is similar to the
security levels defined in the Metadata Service defined by the Fast The hardware version is a simple text string the format of which is
Identity Online (FIDO) Alliance (TODO: reference). set by each manufacturer. The structure and sorting order of this
text string can be specified using the version-scheme item from
CoSWID [CoSWID].
The hardware version can also be given by a 13-digit European Article
Number [EAN-13]. An EAN-13 is also known as an International Article
Number or most commonly as a bar code. This claim is the ASCII text
representation of actual digits often printed with a bar code. Use
of this claim must comply with the EAN allocation and assignment
rules. For example, this requires the manufacturer to obtain a
manufacture code from GS1.
Both the simple version string and EAN-13 versions may be included
for the same hardware.
{::include cddl/hardware-version.cddl}
3.8. Software Description and Version
TODO: Add claims that reference CoSWID.
3.9. The Security Level Claim (security-level)
This claim characterizes the device/entity ability to defend against
attacks aimed at capturing the signing key, forging claims and at
forging EATs. This is done by
defining four security levels as described below. This is similar to
the key protection types defined by the Fast Identity Online (FIDO)
Alliance [FIDO.Registry]).
These claims describe security environment and countermeasures These claims describe security environment and countermeasures
available on the end-entity / client device where the attestation key available on the end-entity / client device where the attestation key
reside and the claims originate. reside and the claims originate.
1 - Unrestricted There is some expectation that implementor will 1 - Unrestricted There is some expectation that implementor will
protect the attestation signing keys at this level. Otherwise the protect the attestation signing keys at this level. Otherwise the
EAT provides no meaningful security assurances. EAT provides no meaningful security assurances.
2- Restricted Entities at this level should not be general-purpose 2- Restricted Entities at this level should not be general-purpose
operating environments that host features such as app download operating environments that host features such as app download
systems, web browsers and complex productivity applications. It systems, web browsers and complex productivity applications. It
is akin to the Secure Restricted level (see below) without the is akin to the Secure Restricted level (see below) without the
security orientation. Examples include a Wi-Fi subsystem, an IoT security orientation. Examples include a Wi-Fi subsystem, an IoT
camera, or sensor device. camera, or sensor device.
3 - Secure Restricted Entities at this level must meet the criteria 3 - Secure Restricted Entities at this level must meet the criteria
defined by FIDO Allowed Restricted Operating Environments (TODO: defined by FIDO Allowed Restricted Operating Environments
reference). Examples include TEE's and schemes using [FIDO.AROE]. Examples include TEE's and schemes using
virtualization-based security. Like the FIDO security goal, virtualization-based security. Like the FIDO security goal,
security at this level is aimed at defending well against large- security at this level is aimed at defending well against large-
scale network / remote attacks against the device. scale network / remote attacks against the device.
4 - Hardware Entities at this level must include substantial defense 4 - Hardware Entities at this level must include substantial defense
against physical or electrical attacks against the device itself. against physical or electrical attacks against the device itself.
It is assumed any potential attacker has captured the device and It is assumed any potential attacker has captured the device and
can disassemble it. Example include TPMs and Secure Elements. can disassemble it. Example include TPMs and Secure Elements.
The entity should claim the highest security level it achieves and no
higher. This set is not extensible so as to provide a common
interoperable description of security level to the relying party. If
a particular implementation considers this claim to be inadequate, it
can define its own proprietary claim. It may consider including both
this claim as a coarse indication of security and its own proprietary
claim as a refined indication.
This claim is not intended as a replacement for a proper end-device This claim is not intended as a replacement for a proper end-device
security certification schemes such as those based on FIPS (TODO: security certification schemes such as those based on FIPS 140
reference) or those based on Common Criteria (TODO: reference). The [FIPS-140] or those based on Common Criteria [Common.Criteria]. The
claim made here is solely a self-claim made by the Entity Originator. claim made here is solely a self-claim made by the Entity Originator.
3.7.1. security-level CDDL 3.9.1. security-level CDDL
security-level-type = &( {::include cddl/security-level.cddl}
unrestricted: 1,
restricted: 2,
secure-restricted: 3,
hardware: 4
)
security-level-claim = ( 3.10. Secure Boot Claim (secure-boot)
security-level => security-level-type
)
3.8. Secure Boot and Debug Enable State Claims (boot-state) The value of true indicates secure boot is enabled. Secure boot is
considered enabled when base software, the firmware and operating
system, are under control of the entity manufacturer identified in
the oemid claimd described in Section 3.6. This may because the
software is in ROM or because it is cryptographically authenticated
or some combination of the two or other.
This claim is an array of five Boolean values indicating the boot and 3.10.1. secure-boot CDDL
debug state of the entity.
3.8.1. Secure Boot Enabled {::include cddl/secure-boot.cddl}
This indicates whether secure boot is enabled either for an entire 3.11. Debug Status Claim (debug-status)
device or an individual submodule. If it appears at the device
level, then this means that secure boot is enabled for all
submodules. Secure boot enablement allows a secure boot loader to
authenticate software running either in a device or a submodule prior
allowing execution.
3.8.2. Debug Disabled This applies to system-wide or submodule-wide debug facilities of the
target device / submodule like JTAG and diagnostic hardware built
into chips. It applies to any software debug facilities related to
root, operating system or privileged software that allow system-wide
memory inspection, tracing or modification of non-system software
like user mode applications.
This indicates whether debug capabilities are disabled for an entity This characterization assumes that debug facilities can be enabled
(i.e. value of 'true'). Debug disablement is considered a and disabled in a dynamic way or be disabled in some permanent way
prerequisite before an entity is considered operational. such that no enabling is possible. An example of dynamic enabling is
one where some authentication is required to enable debugging. An
example of permanent disabling is blowing a hardware fuse in a chip.
The specific type of the mechanism is not taken into account. For
example, it does not matter if authentication is by a global password
or by per-device public keys.
3.8.3. Debug Disabled Since Boot As with all claims, the absence of the debug level claim means it is
not reported. A conservative interpretation might assume the Not
Disabled state. It could however be that it is reported in a
proprietary claim.
This claim indicates whether debug capabilities for the entity were This claim is not extensible so as to provide a common interoperable
not disabled in any way since boot (i.e. value of 'true'). description of debug status to the relying party. If a particular
implementation considers this claim to be inadequate, it can define
its own proprietary claim. It may consider including both this claim
as a coarse indication of debug status and its own proprietary claim
as a refined indication.
3.8.4. Debug Permanent Disable The higher levels of debug disabling requires that all debug
disabling of the levels below it be in effect. Since the lowest
level requires that all of the target's debug be currently disabled,
all other levels require that too.
This claim indicates whether debug capabilities for the entity are There is no inheritance of claims from a submodule to a superior
permanently disabled (i.e. value of 'true'). This value can be set module or vice versa. There is no assumption, requirement or
to 'true' also if only the manufacturer is allowed to enabled debug, guarantee that the target of a superior module encompasses the
but the end user is not. targets of submodules. Thus, every submodule must explicitly
describe its own debug state. The verifier or relying party
receiving an EAT cannot assume that debug is turned off in a
submodule because there is a claim indicating it is turned off in a
superior module.
3.8.5. Debug Full Permanent Disable An individual target device / submodule may have multiple debug
facilities. The use of plural in the description of the states
refers to that, not to any aggregation or inheritance.
This claim indicates whether debug capabilities for the entity are The architecture of some chips or devices may be such that a debug
permanently disabled (i.e. value of 'true'). This value can only be facility operates for the whole chip or device. If the EAT for such
set to 'true' if no party can enable debug capabilities for the a chip includes submodules, then each submodule should independently
entity. Often this is implemented by blowing a fuse on a chip as report the status of the whole-chip or whole-device debug facility.
fuses cannot be restored once blown. This is the only way the relying party can know the debug status of
the submodules since there is no inheritance.
3.8.6. boot-state CDDL 3.11.1. Enabled
boot-state-type = [ If any debug facility, even manufacturer hardware diagnostics, is
secure-boot-enabled => bool, currently enabled, then this level must be indicated.
debug-disabled => bool,
debug-disabled-since-boot => bool,
debug-permanent-disable => bool,
debug-full-permanent-disable => bool
]
boot-state-claim = ( 3.11.2. Disabled
boot-state => boot-state-type
)
3.9. The Location Claim (location) This level indicates all debug facilities are currently disabled. It
may be possible to enable them in the future, and it may also be
possible that they were enabled in the past after the target device/
sub-system booted/started, but they are currently disabled.
The location claim is a CBOR-formatted object that describes the 3.11.3. Disabled Since Boot
location of the device entity from which the attestation originates.
It is comprised of a map of additional sub claims that represent the
actual location coordinates (latitude, longitude and altitude). The
location coordinate claims are consistent with the WGS84 coordinate
system [WGS84]. In addition, a sub claim providing the estimated
accuracy of the location measurement is defined.
3.9.1. location CDDL This level indicates all debug facilities are currently disabled and
have been so since the target device/sub-system booted/started.
location-type = { 3.11.4. Disabled Permanently
latitude => number,
longitude => number,
? altitude => number,
? accuracy => number,
? altitude-accuracy => number,
? heading => number,
? speed => number
}
location-claim = ( This level indicates all non-manufacturer facilities are permanently
location => location-type disabled such that no end user or developer cannot enable them. Only
) the manufacturer indicated in the OEMID claim can enable them. This
also indicates that all debug facilities are currently disabled and
have been so since boot/start.
3.10. The Age Claim (age) 3.11.5. Disabled Fully and Permanently
The "age" claim contains a value that represents the number of This level indicates that all debug capabilities for the target
seconds that have elapsed since the token was created, measurement device/sub-module are permanently disabled.
was made, or location was obtained. Typical attestable values are
sent as soon as they are obtained. However, in the case that such a
value is buffered and sent at a later time and a sufficiently
accurate time reference is unavailable for creation of a timestamp,
then the age claim is provided.
3.10.1. age CDDL 3.11.6. debug-status CDDL
age-claim = ( {::include cddl/debug-status.cddl}
age => uint
)
3.11. The Uptime Claim (uptime) 3.12. Including Keys
An EAT may include a cryptographic key such as a public key. The
signing of the EAT binds the key to all the other claims in the
token.
The purpose for inclusion of the key may vary by use case. For
example, the key may be included as part of an IoT device onboarding
protocol. When the FIDO protocol includes a pubic key in its
attestation message, the key represents the binding of a user, device
and relying party. This document describes how claims containing
keys should be defined for the various use cases. It does not define
specific claims for specific use cases.
Keys in CBOR format tokens SHOULD be the COSE_Key format [RFC8152]
and keys in JSON format tokens SHOULD be the JSON Web Key format
[RFC7517]. These two formats support many common key types. Their
use avoids the need to decode other serialization formats. These two
formats can be extended to support further key types through their
IANA registries.
The general confirmation claim format [RFC8747], [RFC7800] may also
be used. It provides key encryption. It also allows for inclusion
by reference through a key ID. The confirmation claim format may
employed in the definition of some new claim for a a particular use
case.
When the actual confirmation claim is included in an EAT, this
document associates no use case semantics other than proof of
posession. Different EAT use cases may choose to associate further
semantics. The key in the confirmation claim MUST be protected the
same as the key used to sign the EAT. That is, the same, equivalent
or better hardware defenses, access controls, key generation and such
must be used.
3.13. The Location Claim (location)
The location claim gives the location of the device entity from which
the attestation originates. It is derived from the W3C Geolocation
API [W3C.GeoLoc]. The latitude, longitude, altitude and accuracy
must conform to [WGS84]. The altitude is in meters above the [WGS84]
ellipsoid. The two accuracy values are positive numbers in meters.
The heading is in degrees relative to true north. If the device is
stationary, the heading is NaN (floating-point not-a-number). The
speed is the horizontal component of the device velocity in meters
per second.
When encoding floating-point numbers half-precision should not be
used. It usually does not provide enough precision for a geographic
location. It is not a requirement that the receiver of an EAT
implement half-precision, so the receiver may not be able to decode
the location.
The location may have been cached for a period of time before token
creation. For example, it might have been minutes or hours or more
since the last contact with a GPS satellite. Either the timestamp or
age data item can be used to quantify the cached period. The
timestamp data item is preferred as it a non-relative time.
The age data item can be used when the entity doesn't know what time
it is either because it doesn't have a clock or it isn't set. The
entity must still have a "ticker" that can measure a time interval.
The age is the interval between acquisition of the location data and
token creation.
See {#locationprivacyconsiderations} below.
3.13.1. location CDDL
{::include cddl/location.cddl}
3.14. The Uptime Claim (uptime)
The "uptime" claim contains a value that represents the number of The "uptime" claim contains a value that represents the number of
seconds that have elapsed since the entity or submod was last booted. seconds that have elapsed since the entity or submod was last booted.
3.11.1. uptime CDDL 3.14.1. uptime CDDL
uptime-claim = ( {::include cddl/uptime.cddl}
uptime => uint
3.15. The Intended Use Claim (intended-use)
EAT's may be used in the context of several different applications.
The intended-use claim provides an indication to an EAT consumer
about the intended usage of the token. This claim can be used as a
way for an application using EAT to internally distinguish between
different ways it uses EAT.
1 - Generic Generic attestation describes an application where the
EAT consumer requres the most up-to-date security assessment of
the attesting entity. It is expected that this is the most
commonly-used application of EAT.
2- Registration Entities that are registering for a new service may
be expected to provide an attestation as part of the registration
process. This intended-use setting indicates that the attestation
is not intended for any use but registration.
3 - Provisioning Entities may be provisioned with different values
or settings by an EAT consumer. Examples include key material or
device management trees. The consumer may require an EAT to
assess device security state of the entity prior to provisioning.
4 - Certificate Issuance (Certificate Signing Request) Certifying
authorities (CA's) may require attestations prior to the issuance
of certificates related to keypairs hosted at the entity. An EAT
may be used as part of the certificate signing request (CSR).
5 - Proof-of-Possession An EAT consumer may require an attestation
as part of an accompanying proof-of-possession (PoP) appication.
More precisely, a PoP transaction is intended to provide to the
recipient cryptographically-verifiable proof that the sender has
posession of a key. This kind of attestation may be neceesary to
verify the security state of the entity storing the private key
used in a PoP application.
3.15.1. intended-use CDDL
intended-use = &(
generic: 1,
registration: 2,
provisioning: 3,
csr: 4,
pop: 5
) )
3.12. The Submods Part of a Token (submods) 3.16. The Submodules Part of a Token (submods)
Some devices are complex, having many subsystems or submodules. A Some devices are complex, having many subsystems or submodules. A
mobile phone is a good example. It may have several connectivity mobile phone is a good example. It may have several connectivity
submodules for communications (e.g., Wi-Fi and cellular). It may submodules for communications (e.g., Wi-Fi and cellular). It may
have subsystems for low-power audio and video playback. It may have have subsystems for low-power audio and video playback. It may have
one or more security-oriented subsystems like a TEE or a Secure one or more security-oriented subsystems like a TEE or a Secure
Element. Element.
The claims for each these can be grouped together in a submodule. The claims for each these can be grouped together in a submodule.
The submods part of a token a single map/object with many entries, The submods part of a token are in a single map/object with many
one per submodule. There is only one submods map in a token. It is entries, one per submodule. There is only one submods map in a
identified by its specific label. It is a peer to other claims, but token. It is identified by its specific label. It is a peer to
it is not called a claim because it is a container for a claim set other claims, but it is not called a claim because it is a container
rather than an individual claim. This submods part of a token allows for a claim set rather than an individual claim. This submods part
what might be called recursion. It allows claim sets inside of claim of a token allows what might be called recursion. It allows claim
sets inside of claims sets... sets inside of claim sets inside of claims sets...
3.12.1. Two Types of Submodules 3.16.1. Two Types of Submodules
Each entry in the submod map one of two types: Each entry in the submod map is one of two types:
o A non-token submodule that is a map or object directly containing o A non-token submodule that is a map or object directly containing
claims for the submodule. claims for the submodule.
o A nested EAT that is a fully-formed, independently signed EAT o A nested EAT that is a fully formed, independently signed EAT
token token
3.12.1.1. Non-token Submodules 3.16.1.1. Non-token Submodules
Essentially this type of submodule, is just a sub-map or sub-object This is simply a map or object containing claims about the submodule.
containing claims. It is recognized from the other type by being a
data item of type map in CBOR or by being an object in JSON.
The contents are claims about the submodule of types defined in this It may contain claims that are the same as its surrounding token or
document or anywhere else claims types are defined. superior submodules. For example, the top-level of the token may
have a UEID, a submod may have a different UEID and a further
subordinate submodule may also have a UEID.
3.12.1.2. Nested EATs It is signed/encrypted along with the rest of the token and thus the
claims are secured by the same Attester with the same signing key as
the rest of the token.
This type of submodule is a fully formed EAT as described here. In If a token is in CBOR format (a CWT or a UCCS), all non-token
this case the submodule has key material distinct from the containing submodules must be CBOR format. If a token in in JSON format (a
EAT token that allows it to sign on its own. JWT), all non-token submodules must be in JSON format.
When an EAT is nested in another EAT as a submodule the nested EAT When decoding, this type of submodule is recognized from the other
MUST use the CBOR CWT tag. This clearly distinguishes it from the type by being a data item of type map for CBOR or type object for
non-token submodules. JSON.
3.12.2. No Inheritance 3.16.1.2. Nested EATs
This type of submodule is a fully formed secured EAT as defined in
this document except that it MUST NOT be a UCCS or an unsecured JWT.
A nested token that is one that is always secured using COSE or JOSE,
usually by an independent Attester. When the surrounding EAT is a
CWT or secured JWT, the nested token becomes securely bound with the
other claims in the surrounding token.
It is allowed to have a CWT as a submodule in a JWT and vice versa,
but this SHOULD be avoided unless necessary.
3.16.1.2.1. Surrounding EAT is CBOR format
They type of an EAT nested in a CWT is determined by whether the CBOR
type is a text string or a byte string. If a text string, then it is
a JWT. If a byte string, then it is a CWT.
A CWT nested in a CBOR-format token is always wrapped by a byte
string for easier handling with standard CBOR decoders and token
processing APIs that will typically take a byte buffer as input.
Nested CWTs may be either a CWT CBOR tag or a CWT Protocol Message.
COSE layers in nested CWT EATs MUST be a COSE_Tagged_Message, never a
COSE_Untagged_Message. If a nested EAT has more than one level of
COSE, for example one that is both encrypted and signed, a
COSE_Tagged_message must be used at every level.
3.16.1.2.2. Surrounding EAT is JSON format
When a CWT is nested in a JWT, it must be as a 55799 tag in order to
distinguish it from a nested JWT.
When a nested EAT in a JWT is decoded, first remove the base64url
encoding. Next, check to see if it starts with the bytes 0xd9d9f7.
If so, then it is a CWT as a JWT will never start with these four
bytes. If not if it is a JWT.
Other than the 55799 tag requirement, tag usage for CWT's nested in a
JSON format token follow the same rules as for CWTs nested in CBOR-
format tokens. It may be a CWT CBOR tag or a CWT Protocol Message
and COSE_Tagged_Message MUST be used at all COSE layers.
3.16.1.3. Unsecured JWTs and UCCS Tokens as Submodules
To incorporate a UCCS token as a submodule, it MUST be as a non-token
submodule. This can be accomplished inserting the content of the
UCCS Tag into the submodule map. The content of a UCCS tag is
exactly a map of claims as required for a non-token submodule. If
the UCCS is not a UCCS tag, then it can just be inserted into the
submodule map directly.
The definition of a nested EAT type of submodule is that it is one
that is secured (signed) by an Attester. Since UCCS tokens are
unsecured, they do not fulfill this definition and must be non-token
submodules.
To incorporate an Unsecured JWT as a submodule, the null-security
JOSE wrapping should be removed. The resulting claims set should be
inserted as a non-token submodule.
To incorporate a UCCS token in a surrounding JSON token, the UCCS
token claims should be translated from CBOR to JSON. To incorporate
an Unsecured JWT into a surrounding CBOR-format token, the null-
security JOSE should be removed and the claims translated from JSON
to CBOR.
3.16.2. No Inheritance
The subordinate modules do not inherit anything from the containing The subordinate modules do not inherit anything from the containing
token. The subordinate modules must explicitly include all of their token. The subordinate modules must explicitly include all of their
claims. This is the case even for claims like the nonce and age. claims. This is the case even for claims like the nonce and age.
This rule is in place for simplicity. It avoids complex inheritance This rule is in place for simplicity. It avoids complex inheritance
rules that might vary from one type of claim to another. (TODO: fix rules that might vary from one type of claim to another.
the boot claim which does have inheritance as currently described).
3.12.3. Security Levels 3.16.3. Security Levels
The security level of the non-token subordinate modules should always The security level of the non-token subordinate modules should always
be less than or equal to that of the containing modules in the case be less than or equal to that of the containing modules in the case
of non-token submodules. It makes no sense for a module of lesser of non-token submodules. It makes no sense for a module of lesser
security to be signing claims of a module of higher security. An security to be signing claims of a module of higher security. An
example of this is a TEE signing claims made by the non-TEE parts example of this is a TEE signing claims made by the non-TEE parts
(e.g. the high-level OS) of the device. (e.g. the high-level OS) of the device.
The opposite may be true for the nested tokens. They usually have The opposite may be true for the nested tokens. They usually have
their own more secure key material. An example of this is an their own more secure key material. An example of this is an
embedded secure element. embedded secure element.
3.12.4. Submodule Names 3.16.4. Submodule Names
The label or name for each submodule in the submods map is a text The label or name for each submodule in the submods map is a text
string naming the submodule. No submodules may have the same name. string naming the submodule. No submodules may have the same name.
3.12.5. submods CDDL 3.16.5. submods CDDL
submods-type = { + submodule }
submodule = ( {::include cddl/submods.cddl}
submod_name => eat-claims / eat-token
)
submod_name = tstr / int 4. Endorsements and Verification Keys
submods-part = ( TODO: fill this section in. It will discuss key IDs, endorsement ID
submods => submod-type and such that are needed as input needed to by the Verifier to verify
) the signature. This will NOT discuss the contents of an Endorsement,
just and ID/locator.
4. Encoding 5. Encoding
This makes use of the types defined in CDDL Appendix D, Standard This makes use of the types defined in CDDL Appendix D, Standard
Prelude. Prelude.
4.1. Common CDDL Types Some of the CDDL included here is for claims that are defined in CWT
[RFC8392] or JWT [RFC7519] or are in the IANA CWT or JWT registries.
CDDL was not in use when these claims where defined.
string-or-uri = uri / tstr; See JSON section below for JSON encoding of string-or-uri 5.1. Common CDDL Types
4.2. CDDL for CWT-defined Claims time-int is identical to the epoch-based time, but disallows
floating-point representation.
{::include cddl/common-types.cddl}
5.2. CDDL for CWT-defined Claims
This section provides CDDL for the claims defined in CWT. It is non- This section provides CDDL for the claims defined in CWT. It is non-
normative as [RFC8392] is the authoritative definition of these normative as [RFC8392] is the authoritative definition of these
claims. claims.
rfc8392-claim //= ( issuer => text ) {::include cddl/cwt.cddl}
rfc8392-claim //= ( subject => text )
rfc8392-claim //= ( audience => text )
rfc8392-claim //= ( expiration => time )
rfc8392-claim //= ( not-before => time )
rfc8392-claim //= ( issued-at => time )
rfc8392-claim //= ( cwt-id => bytes )
issuer = 1
subject = 2
audience = 3
expiration = 4
not-before = 5
issued-at = 6
cwt-id = 7
cwt-claim = rfc8392-claim
4.3. JSON 5.3. JSON
4.3.1. JSON Labels 5.3.1. JSON Labels
ueid = "ueid"
origination = "origination"
oemid = "oemid"
security-level = "security-level"
boot-state = "boot-state"
location = "location"
age = "age"
uptime = "uptime"
nested-eat = "nested-eat"
submods = "submods"
latitude = "lat" {::include cddl/json.cddl}
longitude = "long""
altitude = "alt"
accuracy = "accry"
altitude-accuracy = "alt-accry"
heading = "heading"
speed = "speed"
4.3.2. JSON Interoperability 5.3.2. JSON Interoperability
JSON should be encoded per RFC 8610 Appendix E. In addition, the JSON should be encoded per RFC 8610 Appendix E. In addition, the
following CDDL types are encoded in JSON as follows: following CDDL types are encoded in JSON as follows:
o bstr - must be base64url encoded o bstr - must be base64url encoded
o time - must be encoded as NumericDate as described section 2 of o time - must be encoded as NumericDate as described section 2 of
[RFC7519]. [RFC7519].
o string-or-uri - must be encoded as StringOrURI as described o string-or-uri - must be encoded as StringOrURI as described
section 2 of [RFC7519]. section 2 of [RFC7519].
4.4. CBOR 5.4. CBOR
4.4.1. CBOR Labels
ueid = To_be_assigned
origination = To_be_assigned
oemid = To_be_assigned
security-level = To_be_assigned
boot-state = To_be_assigned
location = To_be_assigned
age = To_be_assigned
uptime = To_be_assigned
submods = To_be_assigned
nonce = To_be_assigned
latitude = 1
longitude = 2
altitude = 3
accuracy = 4
altitude-accuracy = 5
heading = 6
speed = 7
4.4.2. CBOR Interoperability 5.4.1. CBOR Interoperability
Variations in the CBOR serializations supported in CBOR encoding and Variations in the CBOR serializations supported in CBOR encoding and
decoding are allowed and suggests that CBOR-based protocols specify decoding are allowed and suggests that CBOR-based protocols specify
how this variation is handled. This section specifies what formats how this variation is handled. This section specifies what formats
MUST be supported in order to achieve interoperability. MUST be supported in order to achieve interoperability.
The assumption is that the entity is likely to be a constrained The assumption is that the entity is likely to be a constrained
device and relying party is likely to be a very capable server. The device and relying party is likely to be a very capable server. The
approach taken is that the entity generating the token can use approach taken is that the entity generating the token can use
whatever encoding it wants, specifically encodings that are easier to whatever encoding it wants, specifically encodings that are easier to
skipping to change at page 22, line 7 skipping to change at page 26, line 10
o Integer Encoding (major type 0, 1) - The entity may use any o Integer Encoding (major type 0, 1) - The entity may use any
integer encoding allowed by CBOR. The server MUST accept all integer encoding allowed by CBOR. The server MUST accept all
integer encodings allowed by CBOR. integer encodings allowed by CBOR.
o String Encoding (major type 2 and 3) - The entity can use any o String Encoding (major type 2 and 3) - The entity can use any
string encoding allowed by CBOR including indefinite lengths. It string encoding allowed by CBOR including indefinite lengths. It
may also encode the lengths of strings in any way allowed by CBOR. may also encode the lengths of strings in any way allowed by CBOR.
The server must accept all string encodings. The server must accept all string encodings.
o Major type 2, bstr, SHOULD be have tag 21 to indicate conversion o Major type 2, bstr, SHOULD have tag 21 to indicate conversion to
to base64url in case that conversion is performed. base64url in case that conversion is performed.
o Map and Array Encoding (major type 4 and 5) - The entity can use o Map and Array Encoding (major type 4 and 5) - The entity can use
any array or map encoding allowed by CBOR including indefinite any array or map encoding allowed by CBOR including indefinite
lengths. Sorting of map keys is not required. Duplicate map keys lengths. Sorting of map keys is not required. Duplicate map keys
are not allowed. The server must accept all array and map are not allowed. The server must accept all array and map
encodings. The server may reject maps with duplicate map keys. encodings. The server may reject maps with duplicate map keys.
o Date and Time - The entity should send dates as tag 1 encoded as o Date and Time - The entity should send dates as tag 1 encoded as
64-bit or 32-bit integers. The entity may not send floating-point 64-bit or 32-bit integers. The entity may not send floating-point
dates. The server must support tag 1 epoch-based dates encoded as dates. The server must support tag 1 epoch-based dates encoded as
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however tag 1 is preferred. The server must support tag 0 UTC however tag 1 is preferred. The server must support tag 0 UTC
dates. dates.
o URIs - URIs should be encoded as text strings and marked with tag o URIs - URIs should be encoded as text strings and marked with tag
32. 32.
o Floating Point - The entity may use any floating-point encoding. o Floating Point - The entity may use any floating-point encoding.
The relying party must support decoding of all types of floating- The relying party must support decoding of all types of floating-
point. point.
o Other types - Use of Other types like bignums, regular expressions o Other types - Other types like bignums, regular expressions and
and such, SHOULD NOT be used. The server MAY support them but is such, SHOULD NOT be used. The server MAY support them but is not
not required to so interoperability is not guaranteed. required to so interoperability is not guaranteed.
4.5. Collected CDDL 5.5. Collected CDDL
A generic-claim is any CBOR map entry or JSON name/value pair. {::include cddl/eat-token.cddl}
eat-claims = { ; the top-level payload that is signed using COSE or JOSE 6. IANA Considerations
* claim
}
claim = ( 6.1. Reuse of CBOR Web Token (CWT) Claims Registry
ueid-claim //
origination-claim //
oemid-claim //
security-level-claim //
boot-state-claim //
location-claim //
age-claim //
uptime-claim //
submods-part //
cwt-claim //
generic-claim-type //
)
eat-token ; This is a set of eat-claims signed using COSE Claims defined for EAT are compatible with those of CWT so the CWT
Claims Registry is re used. No new IANA registry is created. All
EAT claims should be registered in the CWT and JWT Claims Registries.
TODO: copy the rest of the CDDL here (wait until the CDDL is more 6.2. Claim Characteristics
settled so as to avoid copying multiple times)
5. IANA Considerations The following is design guidance for creating new EAT claims,
particularly those to be registered with IANA.
5.1. Reuse of CBOR Web Token (CWT) Claims Registry Much of this guidance is generic and could also be considered when
designing new CWT or JWT claims.
Claims defined for EAT are compatible with those of CWT so the CWT 6.2.1. Interoperability and Relying Party Orientation
Claims Registry is re used. No new IANA registry is created. All
EAT claims should be registered in the CWT and JWT Claims Registries.
5.1.1. Claims Registered by This Document It is a broad goal that EATs can be processed by relying parties in a
general way regardless of the type, manufacturer or technology of the
device from which they originate. It is a goal that there be
general-purpose verification implementations that can verify tokens
for large numbers of use cases with special cases and configurations
for different device types. This is a goal of interoperability of
the semantics of claims themselves, not just of the signing, encoding
and serialization formats.
This is a lofty goal and difficult to achieve broadly requiring
careful definition of claims in a technology neutral way. Sometimes
it will be difficult to design a claim that can represent the
semantics of data from very different device types. However, the
goal remains even when difficult.
6.2.2. Operating System and Technology Neutral
Claims should be defined such that they are not specific to an
operating system. They should be applicable to multiple large high-
level operating systems from different vendors. They should also be
applicable to multiple small embedded operating systems from multiple
vendors and everything in between.
Claims should not be defined such that they are specific to a SW
environment or programming language.
Claims should not be defined such that they are specific to a chip or
particular hardware. For example, they should not just be the
contents of some HW status register as it is unlikely that the same
HW status register with the same bits exists on a chip of a different
manufacturer.
The boot and debug state claims in this document are an example of a
claim that has been defined in this neutral way.
6.2.3. Security Level Neutral
Many use cases will have EATs generated by some of the most secure
hardware and software that exists. Secure Elements and smart cards
are examples of this. However, EAT is intended for use in low-
security use cases the same as high-security use case. For example,
an app on a mobile device may generate EATs on its own.
Claims should be defined and registered on the basis of whether they
are useful and interoperable, not based on security level. In
particular, there should be no exclusion of claims because they are
just used only in low-security environments.
6.2.4. Reuse of Extant Data Formats
Where possible, claims should use already standardized data items,
identifiers and formats. This takes advantage of the expertise put
into creating those formats and improves interoperability.
Often extant claims will not be defined in an encoding or
serialization format used by EAT. It is preferred to define a CBOR
and JSON format for them so that EAT implementations do not require a
plethora of encoders and decoders for serialization formats.
In some cases, it may be better to use the encoding and serialization
as is. For example, signed X.509 certificates and CRLs can be
carried as-is in a byte string. This retains interoperability with
the extensive infrastructure for creating and processing X.509
certificates and CRLs.
6.2.5. Proprietary Claims
EAT allows the definition and use of proprietary claims.
For example, a device manufacturer may generate a token with
proprietary claims intended only for verification by a service
offered by that device manufacturer. This is a supported use case.
In many cases proprietary claims will be the easiest and most obvious
way to proceed, however for better interoperability, use of general
standardized claims is preferred.
6.3. Claims Registered by This Document
o Claim Name: UEID o Claim Name: UEID
o Claim Description: The Universal Entity ID o Claim Description: The Universal Entity ID
o JWT Claim Name: N/A o JWT Claim Name: N/A
o Claim Key: 8 o Claim Key: 8
o Claim Value Type(s): byte string o Claim Value Type(s): byte string
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): *this document* o Specification Document(s): *this document*
skipping to change at page 24, line 5 skipping to change at page 29, line 16
o Claim Key: 8 o Claim Key: 8
o Claim Value Type(s): byte string o Claim Value Type(s): byte string
o Change Controller: IESG o Change Controller: IESG
o Specification Document(s): *this document* o Specification Document(s): *this document*
TODO: add the rest of the claims in here TODO: add the rest of the claims in here
6. Privacy Considerations 7. Privacy Considerations
Certain EAT claims can be used to track the owner of an entity and Certain EAT claims can be used to track the owner of an entity and
therefore, implementations should consider providing privacy- therefore, implementations should consider providing privacy-
preserving options dependent on the intended usage of the EAT. preserving options dependent on the intended usage of the EAT.
Examples would include suppression of location claims for EAT's Examples would include suppression of location claims for EAT's
provided to unauthenticated consumers. provided to unauthenticated consumers.
6.1. UEID Privacy Considerations 7.1. UEID Privacy Considerations
A UEID is usually not privacy-preserving. Any set of relying parties A UEID is usually not privacy-preserving. Any set of relying parties
that receives tokens that happen to be from a single device will be that receives tokens that happen to be from a single device will be
able to know the tokens are all from the same device and be able to able to know the tokens are all from the same device and be able to
track the device. Thus, in many usage situations ueid violates track the device. Thus, in many usage situations ueid violates
governmental privacy regulation. In other usage situations UEID will governmental privacy regulation. In other usage situations UEID will
not be allowed for certain products like browsers that give privacy not be allowed for certain products like browsers that give privacy
for the end user. It will often be the case that tokens will not for the end user. It will often be the case that tokens will not
have a UEID for these reasons. have a UEID for these reasons.
skipping to change at page 25, line 5 skipping to change at page 30, line 13
device, then the device generates a UEID just for that relying device, then the device generates a UEID just for that relying
party by hashing a proofed relying party ID with the main device party by hashing a proofed relying party ID with the main device
UEID. UEID.
Note that some of these privacy preservation strategies result in Note that some of these privacy preservation strategies result in
multiple UEIDs per device. Each UEID is used in a different context, multiple UEIDs per device. Each UEID is used in a different context,
use case or system on the device. However, from the view of the use case or system on the device. However, from the view of the
relying party, there is just one UEID and it is still globally relying party, there is just one UEID and it is still globally
universal across manufacturers. universal across manufacturers.
7. Security Considerations 7.2. Location Privacy Considerations
Geographic location is most always considered personally identifiable
information. Implementers should consider laws and regulations
governing the transmission of location data from end user devices to
servers and services. Implementers should consider using location
management facilities offered by the operating system on the device
generating the attestation. For example, many mobile phones prompt
the user for permission when before sending location data.
8. Security Considerations
The security considerations provided in Section 8 of [RFC8392] and The security considerations provided in Section 8 of [RFC8392] and
Section 11 of [RFC7519] apply to EAT in its CWT and JWT form, Section 11 of [RFC7519] apply to EAT in its CWT and JWT form,
respectively. In addition, implementors should consider the respectively. In addition, implementors should consider the
following. following.
7.1. Key Provisioning 8.1. Key Provisioning
Private key material can be used to sign and/or encrypt the EAT, or Private key material can be used to sign and/or encrypt the EAT, or
can be used to derive the keys used for signing and/or encryption. can be used to derive the keys used for signing and/or encryption.
In some instances, the manufacturer of the entity may create the key In some instances, the manufacturer of the entity may create the key
material separately and provision the key material in the entity material separately and provision the key material in the entity
itself. The manfuacturer of any entity that is capable of producing itself. The manfuacturer of any entity that is capable of producing
an EAT should take care to ensure that any private key material be an EAT should take care to ensure that any private key material be
suitably protected prior to provisioning the key material in the suitably protected prior to provisioning the key material in the
entity itself. This can require creation of key material in an entity itself. This can require creation of key material in an
enclave (see [RFC4949] for definition of "enclave"), secure enclave (see [RFC4949] for definition of "enclave"), secure
transmission of the key material from the enclave to the entity using transmission of the key material from the enclave to the entity using
an appropriate protocol, and persistence of the private key material an appropriate protocol, and persistence of the private key material
in some form of secure storage to which (preferably) only the entity in some form of secure storage to which (preferably) only the entity
has access. has access.
7.1.1. Transmission of Key Material 8.1.1. Transmission of Key Material
Regarding transmission of key material from the enclave to the Regarding transmission of key material from the enclave to the
entity, the key material may pass through one or more intermediaries. entity, the key material may pass through one or more intermediaries.
Therefore some form of protection ("key wrapping") may be necessary. Therefore some form of protection ("key wrapping") may be necessary.
The transmission itself may be performed electronically, but can also The transmission itself may be performed electronically, but can also
be done by human courier. In the latter case, there should be be done by human courier. In the latter case, there should be
minimal to no exposure of the key material to the human (e.g. minimal to no exposure of the key material to the human (e.g.
encrypted portable memory). Moreover, the human should transport the encrypted portable memory). Moreover, the human should transport the
key material directly from the secure enclave where it was created to key material directly from the secure enclave where it was created to
a destination secure enclave where it can be provisioned. a destination secure enclave where it can be provisioned.
7.2. Transport Security 8.2. Transport Security
As stated in Section 8 of [RFC8392], "The security of the CWT relies As stated in Section 8 of [RFC8392], "The security of the CWT relies
upon on the protections offered by COSE". Similar considerations upon on the protections offered by COSE". Similar considerations
apply to EAT when sent as a CWT. However, EAT introduces the concept apply to EAT when sent as a CWT. However, EAT introduces the concept
of a nonce to protect against replay. Since an EAT may be created by of a nonce to protect against replay. Since an EAT may be created by
an entity that may not support the same type of transport security as an entity that may not support the same type of transport security as
the consumer of the EAT, intermediaries may be required to bridge the consumer of the EAT, intermediaries may be required to bridge
communications between the entity and consumer. As a result, it is communications between the entity and consumer. As a result, it is
RECOMMENDED that both the consumer create a nonce, and the entity RECOMMENDED that both the consumer create a nonce, and the entity
leverage the nonce along with COSE mechanisms for encryption and/or leverage the nonce along with COSE mechanisms for encryption and/or
signing to create the EAT. signing to create the EAT.
Similar considerations apply to the use of EAT as a JWT. Although Similar considerations apply to the use of EAT as a JWT. Although
the security of a JWT leverages the JSON Web Encryption (JWE) and the security of a JWT leverages the JSON Web Encryption (JWE) and
JSON Web Signature (JWS) specifications, it is still recommended to JSON Web Signature (JWS) specifications, it is still recommended to
make use of the EAT nonce. make use of the EAT nonce.
7.3. Multiple EAT Consumers 8.3. Multiple EAT Consumers
In many cases, more than one EAT consumer may be required to fully In many cases, more than one EAT consumer may be required to fully
verify the entity attestation. Examples include individual consumers verify the entity attestation. Examples include individual consumers
for nested EATs, or consumers for individual claims with an EAT. for nested EATs, or consumers for individual claims with an EAT.
When multiple consumers are required for verification of an EAT, it When multiple consumers are required for verification of an EAT, it
is important to minimize information exposure to each consumer. In is important to minimize information exposure to each consumer. In
addition, the communication between multiple consumers should be addition, the communication between multiple consumers should be
secure. secure.
For instance, consider the example of an encrypted and signed EAT For instance, consider the example of an encrypted and signed EAT
skipping to change at page 26, line 36 skipping to change at page 32, line 7
subsets to any downstream consumer should leverage a secure protocol subsets to any downstream consumer should leverage a secure protocol
(e.g.one that uses transport-layer security, i.e. TLS), (e.g.one that uses transport-layer security, i.e. TLS),
However, assume the EAT of the previous example is hierarchical and However, assume the EAT of the previous example is hierarchical and
each claim subset for a downstream consumer is created in the form of each claim subset for a downstream consumer is created in the form of
a nested EAT. Then transport security between the receiving and a nested EAT. Then transport security between the receiving and
downstream consumers is not strictly required. Nevertheless, downstream consumers is not strictly required. Nevertheless,
downstream consumers of a nested EAT should provide a nonce unique to downstream consumers of a nested EAT should provide a nonce unique to
the EAT they are consuming. the EAT they are consuming.
8. References 9. References
8.1. Normative References 9.1. Normative References
[CoSWID] "Concise Software Identification Tags", November 2020,
<https://tools.ietf.org/html/draft-ietf-sacm-coswid-16>.
[EAN-13] GS1, "International Article Number - EAN/UPC barcodes",
2019, <https://www.gs1.org/standards/barcodes/ean-upc>.
[FIDO.AROE]
The FIDO Alliance, "FIDO Authenticator Allowed Restricted
Operating Environments List", November 2019,
<https://fidoalliance.org/specs/fido-uaf-v1.0-fd-20191115/
fido-allowed-AROE-v1.0-fd-20191115.html>.
[IANA.CWT.Claims] [IANA.CWT.Claims]
IANA, "CBOR Web Token (CWT) Claims", IANA, "CBOR Web Token (CWT) Claims",
<http://www.iana.org/assignments/cwt>. <http://www.iana.org/assignments/cwt>.
[IANA.JWT.Claims] [IANA.JWT.Claims]
IANA, "JSON Web Token (JWT) Claims", IANA, "JSON Web Token (JWT) Claims",
<https://www.iana.org/assignments/jwt>. <https://www.iana.org/assignments/jwt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>. October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/info/rfc7517>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>. <https://www.rfc-editor.org/info/rfc7519>.
[RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of-
Possession Key Semantics for JSON Web Tokens (JWTs)",
RFC 7800, DOI 10.17487/RFC7800, April 2016,
<https://www.rfc-editor.org/info/rfc7800>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)", [RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017, RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/info/rfc8152>. <https://www.rfc-editor.org/info/rfc8152>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
skipping to change at page 27, line 36 skipping to change at page 33, line 28
[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/info/rfc8392>. May 2018, <https://www.rfc-editor.org/info/rfc8392>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/info/rfc8610>. June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[RFC8747] Jones, M., Seitz, L., Selander, G., Erdtman, S., and H.
Tschofenig, "Proof-of-Possession Key Semantics for CBOR
Web Tokens (CWTs)", RFC 8747, DOI 10.17487/RFC8747, March
2020, <https://www.rfc-editor.org/info/rfc8747>.
[ThreeGPP.IMEI] [ThreeGPP.IMEI]
3GPP, "3rd Generation Partnership Project; Technical 3GPP, "3rd Generation Partnership Project; Technical
Specification Group Core Network and Terminals; Numbering, Specification Group Core Network and Terminals; Numbering,
addressing and identification", 2019, addressing and identification", 2019,
<https://portal.3gpp.org/desktopmodules/Specifications/ <https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=729>. SpecificationDetails.aspx?specificationId=729>.
[TIME_T] The Open Group Base Specifications, "Vol. 1: Base [TIME_T] The Open Group Base Specifications, "Vol. 1: Base
Definitions, Issue 7", Section 4.15 'Seconds Since the Definitions, Issue 7", Section 4.15 'Seconds Since the
Epoch', IEEE Std 1003.1, 2013 Edition, 2013, Epoch', IEEE Std 1003.1, 2013 Edition, 2013,
<http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/ <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/
V1_chap04.html#tag_04_15>. V1_chap04.html#tag_04_15>.
[UCCS.Draft]
Birkholz, H., "A CBOR Tag for Unprotected CWT Claims
Sets", 2020,
<https://tools.ietf.org/html/draft-birkholz-rats-uccs-01>.
[WGS84] National Imagery and Mapping Agency, "National Imagery and [WGS84] National Imagery and Mapping Agency, "National Imagery and
Mapping Agency Technical Report 8350.2, Third Edition", Mapping Agency Technical Report 8350.2, Third Edition",
2000, <http://earth- 2000, <http://earth-
info.nga.mil/GandG/publications/tr8350.2/wgs84fin.pdf>. info.nga.mil/GandG/publications/tr8350.2/wgs84fin.pdf>.
8.2. Informative References 9.2. Informative References
[ASN.1] International Telecommunication Union, "Information [ASN.1] International Telecommunication Union, "Information
Technology -- ASN.1 encoding rules: Specification of Basic Technology -- ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", ITU-T Recommendation Distinguished Encoding Rules (DER)", ITU-T Recommendation
X.690, 1994. X.690, 1994.
[BirthdayAttack] [BirthdayAttack]
"Birthday attack", "Birthday attack",
<https://en.wikipedia.org/wiki/Birthday_attack.>. <https://en.wikipedia.org/wiki/Birthday_attack.>.
[Common.Criteria]
"Common Criteria for Information Technology Security
Evaluation", April 2017,
<https://www.commoncriteriaportal.org/cc/>.
[ECMAScript] [ECMAScript]
"Ecma International, "ECMAScript Language Specification, "Ecma International, "ECMAScript Language Specification,
5.1 Edition", ECMA Standard 262", June 2011, 5.1 Edition", ECMA Standard 262", June 2011,
<http://www.ecma-international.org/ecma-262/5.1/ECMA- <http://www.ecma-international.org/ecma-262/5.1/ECMA-
262.pdf>. 262.pdf>.
[FIDO.Registry]
The FIDO Alliance, "FIDO Registry of Predefined Values",
December 2019, <https://fidoalliance.org/specs/common-
specs/fido-registry-v2.1-ps-20191217.html>.
[FIPS-140]
National Institue of Standards, "Security Requirements for
Cryptographic Modules", May 2001,
<https://csrc.nist.gov/publications/detail/fips/140/2/
final>.
[IDevID] "IEEE Standard, "IEEE 802.1AR Secure Device Identifier"", [IDevID] "IEEE Standard, "IEEE 802.1AR Secure Device Identifier"",
December 2009, <http://standards.ieee.org/findstds/ December 2009, <http://standards.ieee.org/findstds/
standard/802.1AR-2009.html>. standard/802.1AR-2009.html>.
[IEEE.802-2001] [IEEE.802-2001]
"IEEE Standard For Local And Metropolitan Area Networks "IEEE Standard For Local And Metropolitan Area Networks
Overview And Architecture", 2007, Overview And Architecture", 2007,
<https://webstore.ansi.org/standards/ieee/ <https://webstore.ansi.org/standards/ieee/
ieee8022001r2007>. ieee8022001r2007>.
skipping to change at page 29, line 9 skipping to change at page 35, line 30
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122, Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005, DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>. <https://www.rfc-editor.org/info/rfc4122>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", [RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007, FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<https://www.rfc-editor.org/info/rfc4949>. <https://www.rfc-editor.org/info/rfc4949>.
[W3C.GeoLoc]
Worldwide Web Consortium, "Geolocation API Specification
2nd Edition", January 2018, <https://www.w3.org/TR/
geolocation-API/#coordinates_interface>.
[Webauthn] [Webauthn]
Worldwide Web Consortium, "Web Authentication: A Web API Worldwide Web Consortium, "Web Authentication: A Web API
for accessing scoped credentials", 2016. for accessing scoped credentials", 2016.
Appendix A. Examples Appendix A. Examples
A.1. Very Simple EAT A.1. Very Simple EAT
This is shown in CBOR diagnostic form. Only the payload signed by This is shown in CBOR diagnostic form. Only the payload signed by
COSE is shown. COSE is shown.
{ {::include cddl/examples/simple.diag}
/ nonce / 9:h'948f8860d13a463e8e',
/ UEID / 10:h'0198f50a4ff6c05861c8860d13a638ea4fe2f',
/ boot-state / 12:{true, true, true, true, false}
/ time stamp (iat) / 6:1526542894,
}
A.2. Example with Submodules, Nesting and Security Levels A.2. Example with Submodules, Nesting and Security Levels
{ {::include cddl/examples/submods.diag}
/ nonce / 9:h'948f8860d13a463e8e',
/ UEID / 10:h'0198f50a4ff6c05861c8860d13a638ea4fe2f',
/ boot-state / 12:{true, true, true, true, false}
/ time stamp (iat) / 6:1526542894,
/ seclevel / 11:3, / secure restricted OS /
/ submods / 17:
{
/ first submod, an Android Application / "Android App Foo" : {
/ seclevel / 11:1, / unrestricted /
/ app data / -70000:'text string'
},
/ 2nd submod, A nested EAT from a secure element / "Secure Element Eat" :
/ eat / 61( 18(
/ an embedded EAT, bytes of which are not shown /
))
/ 3rd submod, information about Linux Android / "Linux Android": {
/ seclevel / 11:1, / unrestricted /
/ custom - release / -80000:'8.0.0',
/ custom - version / -80001:'4.9.51+'
}
}
}
Appendix B. UEID Design Rationale Appendix B. UEID Design Rationale
B.1. Collision Probability B.1. Collision Probability
This calculation is to determine the probability of a collision of This calculation is to determine the probability of a collision of
UEIDs given the total possible entity population and the number of UEIDs given the total possible entity population and the number of
entities in a particular entity management database. entities in a particular entity management database.
Three different sized databases are considered. The number of Three different sized databases are considered. The number of
skipping to change at page 34, line 18 skipping to change at page 39, line 39
This list is non-authoritative. It is meant to help reviewers see This list is non-authoritative. It is meant to help reviewers see
the significant differences. the significant differences.
C.1. From draft-rats-eat-01 C.1. From draft-rats-eat-01
o Added UEID design rationale appendix o Added UEID design rationale appendix
C.2. From draft-mandyam-rats-eat-00 C.2. From draft-mandyam-rats-eat-00
This is a fairly large change in the orientation of the document, but This is a fairly large change in the orientation of the document, but
not new claims have been added. no new claims have been added.
o Separate information and data model using CDDL. o Separate information and data model using CDDL.
o Say an EAT is a CWT or JWT o Say an EAT is a CWT or JWT
o Use a map to structure the boot_state and location claims o Use a map to structure the boot_state and location claims
C.3. From draft-ietf-rats-eat-01 C.3. From draft-ietf-rats-eat-01
o Clarifications and corrections for OEMID claim o Clarifications and corrections for OEMID claim
skipping to change at page 35, line 5 skipping to change at page 40, line 21
o Added appendix justifying UEID design and size. o Added appendix justifying UEID design and size.
o Submods part now includes nested eat tokens so they can be named o Submods part now includes nested eat tokens so they can be named
and there can be more tha one of them and there can be more tha one of them
o Lots of fixes to the CDDL o Lots of fixes to the CDDL
o Added security considerations o Added security considerations
C.5. From draft-ietf-rats-eat-03
o Split boot_state into secure-boot and debug-disable claims
o Debug disable is an enumerated type rather than Booleans
C.6. From draft-ietf-rats-eat-04
o Change IMEI-based UEIDs to be encoded as a 14-byte string
o CDDL cleaned up some more
o CDDL allows for JWTs and UCCSs
o CWT format submodules are byte string wrapped
o Allows for JWT nested in CWT and vice versa
o Allows UCCS (unsigned CWTs) and JWT unsecured tokens
o Clarify tag usage when nesting tokens
o Add section on key inclusion
o Add hardware version claims
o Collected CDDL is now filled in. Other CDDL corrections.
o Rename debug-disable to debug-status; clarify that it is not
extensible
o Security level claim is not extensible
o Improve specification of location claim and added a location
privacy section
o Add intended use claim
Authors' Addresses Authors' Addresses
Giridhar Mandyam Giridhar Mandyam
Qualcomm Technologies Inc. Qualcomm Technologies Inc.
5775 Morehouse Drive 5775 Morehouse Drive
San Diego, California San Diego, California
USA USA
Phone: +1 858 651 7200 Phone: +1 858 651 7200
EMail: mandyam@qti.qualcomm.com EMail: mandyam@qti.qualcomm.com
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