The Entity Attestation Token (EAT)

1.1. Entity Overview

The document uses the term "entity" to refer to the target of the attestation token. The claims defined in this document are claims about an entity.¶

An entity is an implementation in hardware, software or both.¶

An entity is the same as the Attester Target Environment defined in RATS Architecture.¶

An entity also corresponds to a "system component" as defined in the Internet Security Glossary [RFC4949]. That glossary also defines "entity" and "system entity" as something that may be a person or organization as well as a system component. Here "entity" never refers to a person or organization.¶

An entity is never a server or a service.¶

An entity may be the whole device or it may be a subsystem, a subsystem of a subsystem and so on. EAT allows claims to be organized into submodules, nested EATs and so on. See Section 3.25. The entity to which a claim applies is the submodule in which it appears, or to the top-level entity if it doesn't appear in a submodule.¶

Some examples of entities:¶

• A Secure Element¶
• A TEE¶
• A card in a network router¶
• A network router, perhaps with each card in the router a submodule¶
• An IoT device¶
• An individual process¶
• An app on a smartphone¶
• A smartphone with many submodules for its many subsystems¶
• A subsystem in a smartphone like the modem or the camera¶

An entity may have strong security like defenses against hardware invasive attacks. It may also have low security, having no special security defenses. There is no minimum security requirement to be an entity.¶

1.2. CWT, JWT, UCCS, UJCS and DEB

An EAT is a claims set about an entity based on one of the following:¶

• CBOR Web Token (CWT) [RFC8392]¶
• Unprotected CWT Claims Sets (UCCS) [UCCS.Draft]¶
• JSON Web Token (JWT) [RFC7519]¶

All definitions, requirements, creation and validation procedures, security considerations, IANA registrations and so on from these carry over to EAT.¶

This specification extends those specifications by defining additional claims for attestation. This specification also describes the notion of a "profile" that can narrow the definition of an EAT, ensure interoperability and fill in details for specific usage scenarios. This specification also adds some considerations for registration of future EAT-related claims.¶

The identification of a protocol element as an EAT, whether CBOR or JSON encoded, 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.¶

This specification adds two more top-level messages:¶

• Unprotected JWT Claims Set (UJCS) Section 4¶
• Detached EAT Bundle (DEB), Section 5¶

A DEB is structure to hold a collection of detached claims sets and the EAT that separately provides integrity and authenticity protection for them. It can be either CBOR or JSON encoded.¶

1.3. CDDL, CBOR and JSON

This document defines Concise Binary Object Representation (CBOR) [RFC8949] and Javascript Object Notation (JSON) [RFC7159] encoding for an EAT. All claims in an EAT MUST use the same encoding except where explicitly allowed. It is explicitly allowed for a nested token to be of a different encoding. Some claims explicitly contain objects and messages that may use a different encoding than the enclosing EAT.¶

This specification uses Concise Data Definition Language (CDDL) [RFC8610] for all definitions. The implementor interprets the CDDL to come to either the CBOR or JSON encoding. In the case of JSON, Appendix E of [RFC8610] is followed. Additional rules are given in Section 8.2.2 where Appendix E is insufficient.¶

The CWT and JWT specifications were authored before CDDL was available and did not use CDDL. This specification includes a CDDL definition of most of what is defined in [RFC8392]. Similarly, this specification includes CDDL for most of what is defined in [RFC7519].¶

The UCCS specification does not include CDDL. This specification provides CDDL for it.¶

1.4. Operating Model and RATS Architecture

While it is not required that EAT be used with the RATS operational model described in Figure 1 in [RATS.Architecture], or even that it be used for attestation, this document is oriented around that model.¶

To summarize, an Attester generates Attestation Evidence. Attestation Evidence is a claims set describing various characteristics of an entity. Attestation Evidence also is usually signed by a key that proves the entity and the evidence it produces are authentic. The claims set includes a nonce or some other means to provide freshness. EAT is designed to carry Attestation Evidence. The Attestation Evidence goes to a Verifier where the signature is verified. Some of the claims may also be checked against Reference Values. The Verifier then produces Attestation Results which is also usually a claims set. EAT is also designed to carry Attestation Results. The Attestation Results go to the Relying Party which is the ultimate consumer of the Remote Attestation Procedure. The Relying Party uses the Attestation Results as needed for the use case, perhaps allowing an entity on the network, allowing a financial transaction or such.¶

Note that sometimes the Verifier and Relying Party are not separate and thus there is no need for a protocol to carry Attestation Results.¶

3.1. Token ID Claim (cti and jti)

CWT defines the "cti" claim. JWT defines the "jti" claim. These are 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 of the token but are distinct from the nonce that is used by the Relying Party to guarantee freshness and defend against replay.¶

3.2. Timestamp claim (iat)

The "iat" claim defined in CWT and JWT is used to indicate the date-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. An EAT token MUST NOT contain an iat claim in float-point format. Any recipient of a token with a floating-point format iat claim MUST 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)

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 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.¶

This documents the nonce claim for registration in the IANA CWT claims registry. This is equivalent to the JWT nonce claim that is already registered.¶

The nonce must be at least 8 bytes (64 bits) long as fewer bytes are unlikely to 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 already-registered JWT nonce, but it should follow this size recommendation when used in an EAT.¶

Multiple nonces are allowed to accommodate multistage verification and consumption.¶

$$claims-set-claims //=
    (nonce-label => nonce-type / [ 2* nonce-type ])

nonce-type = bstr .size (8..64)

3.4. Universal Entity ID Claim (ueid)

A UEID identifies an individual manufactured entity like a mobile phone, a water meter, a Bluetooth speaker or a networked security camera. It may identify the entire entity or a submodule. It does not identify types, models or classes of entities. It is akin to a serial number, though it does not have to be sequential.¶

UEIDs MUST be universally and globally unique across manufacturers and countries. UEIDs MUST also be unique across protocols and systems, as tokens are intended to be embedded in many different protocols and systems. No two products anywhere, even in completely different industries made by two different manufacturers in two different countries should have the same UEID (if they are not global and universal in this way, then Relying Parties receiving them will have to track other characteristics of the entity to keep entities distinct between manufacturers).¶

There are privacy considerations for UEIDs. See Section 10.1.¶

The UEID is permanent. It MUST never change for a given entity.¶

A UEID is constructed of a single type byte followed by the bytes that are the identifier. Several types are allowed to accommodate different industries, different manufacturing processes and to have an alternative that doesn't require paying a registration fee.¶

Creation of new types requires a Standards Action [RFC8126].¶

UEIDs are variable length. All implementations MUST be able to receive UEIDs that are 33 bytes long (1 type byte and 256 bits). No UEID longer than 33 bytes SHOULD be sent.¶

UEIDs are not designed for direct use by humans (e.g., printing on 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 completely opaque string of bytes and not make any use of its internal structure. For example, they should not use the OUI part of a type 0x02 UEID to identify the manufacturer of the entity. Instead, they should use the OEMID claim. See Section 3.6. The reasons for this are:¶

• UEIDs types may vary freely from one manufacturer to the next.¶
• New types of UEIDs may be created. For example, a type 0x07 UEID may be created based on some other manufacturer registration scheme.¶
• Entity manufacturers are allowed to change from one type of UEID to another anytime they want. For example, they may find they can optimize their manufacturing by switching from type 0x01 to type 0x02 or vice versa. The essential requirement on the manufacturer is that UEIDs be universally unique.¶

A Device Identifier URN is registered for UEIDs. See Section 9.3.4.¶

$$claims-set-claims //= (ueid-label => ueid-type)

ueid-type = bstr .size (7..33)

3.5. Semi-permanent UEIDs (SUEIDs)

An SEUID is of the same format as a UEID, but it MAY change to a different value on device life-cycle events. Examples of these events are change of ownership, factory reset and on-boarding into an IoT device management system. An entity MAY have both a UEID and SUEIDs, neither, one or the other.¶

There MAY be multiple SUEIDs. Each one has a text string label the purpose of which is to distinguish it from others in the token. The label MAY name the purpose, application or type of the SUEID. Typically, there will be few SUEDs so there is no need for a formal labeling mechanism like a registry. The EAT profile MAY describe how SUEIDs should be labeled. If there is only one SUEID, the claim remains a map and there still must be a label. For example, the label for the SUEID used by FIDO Onboarding Protocol could simply be "FDO".¶

There are privacy considerations for SUEIDs. See Section 10.1.¶

A Device Indentifier URN is registered for SUEIDs. See Section 9.3.4.¶

$$claims-set-claims //= (sueids-label => sueids-type)

sueids-type = {
    + tstr => ueid-type
}

3.6. Hardware OEM Identification (oemid)

This claim identifies the Original Equipment Manufacturer (OEM) of the hardware. Any of the three forms described below MAY be used at the convenience of the claim sender. The receiver of this claim MUST be able to handle all three forms.¶

oemid-pen = int

oemid-ieee = bstr .size 3

oemid-random = bstr .size 16


$$claims-set-claims //= (
    oemid-label =>
        oemid-random / oemid-ieee / oemid-pen
)

3.7. Hardware Model Claim (hardware-model)

This claim differentiates hardware models, products and variants manufactured by a particular OEM, the one identified by OEM ID in Section 3.6.¶

This claim must be unique so as to differentiate the models and products for the OEM ID. This claim does not have to be globally unique, but it can be. A receiver of this claim MUST not assume it is globally unique. To globally identify a particular product, the receiver should concatenate the OEM ID and this claim.¶

The granularity of the model identification is for each OEM to decide. It may be very granular, perhaps including some version information. It may be very general, perhaps only indicating top-level products.¶

The purpose of this claim is to identify models within protocols, not for human-readable descriptions. The format and encoding of this claim should not be human-readable to discourage use other than in protocols. If this claim is to be derived from an already-in-use human-readable identifier, it can be run through a hash function.¶

There is no minimum length so that an OEM with a very small number of models can use a one-byte encoding. The maximum length is 32 bytes. All receivers of this claim MUST be able to receive this maximum size.¶

The receiver of this claim MUST treat it as a completely opaque string of bytes, even if there is some apparent naming or structure. The OEM is free to alter the internal structure of these bytes as long as the claim continues to uniquely identify its models.¶

hardware-model-type = bytes .size (1..32)

$$claims-set-claims //= (
    hardware-model-label => hardware-model-type
)

3.8. Hardware Version Claims (hardware-version-claims)

The hardware version is a text string the format of which is set by each manufacturer. The structure and sorting order of this text string can be specified using the version-scheme item from CoSWID [CoSWID]. It is useful to know how to sort versions so the newer can be distinguished from the older.¶

The hardware version can also be given by a 13-digit [EAN-13]. A new CoSWID version scheme is registered with IANA by this document in Section 9.3.3. An EAN-13 is also known as an International Article Number or most commonly as a bar code.¶

$$claims-set-claims //=  (
    hardware-version-label => hardware-version-type
)

hardware-version-type = [
    version:  tstr,
    scheme:  $version-scheme
]

3.9. Software Name Claim

This is a free-form text claim for the name of the software for the entity or submodule. A CoSWID manifest or other type of manifest can be used instead if this claim is to limited to correctly characterize the SW for the entity or submodule.¶

$$claims-set-claims //= ( sw-name-label => tstr )

3.10. Software Version Claim

This makes use of the CoSWID version scheme data type to give a simple version for the software. A full CoSWID manifest or other type of manifest can be instead if this is too simple.¶

$$claims-set-claims //= (sw-version-label => sw-version-type)

sw-version-type = [
    version:  tstr,
    scheme:  $version-scheme ; As defined by CoSWID
]

3.11. The Security Level Claim (security-level)

This claim characterizes the entity's ability to defend against attacks aimed at capturing the signing key, forging claims and at forging EATs. This is by defining four security levels.¶

This claim describes the security environment and countermeasures available on the entity where the attestation key resides and the claims originate.¶

1 - Unrestricted:

There is some expectation that implementor will protect the attestation signing keys at this level. Otherwise, the EAT provides no meaningful security assurances.¶

2 - Restricted:

Entities at this level are not general-purpose operating environments that host features, such as app download systems, web browsers and complex applications. It is akin to the secure-restricted level (see below) without the security orientation. Examples include a Wi-Fi subsystem, an IoT camera, or sensor device. Often these can be considered more secure than unrestricted just because they are much simpler and a smaller attack surface, but this won't always be the case. Some unrestricted devices may be implemented in a way that provides poor protection of signing keys.¶

3 - Secure-Restricted:

Entities at this level must meet the criteria defined in Section 4 of FIDO Allowed Restricted Operating Environments [FIDO.AROE]. Examples include TEE's and schemes using virtualization-based security. Security at this level is aimed at defending against large-scale network/remote attacks against the entity.¶

4 - Hardware:

Entities at this level must include substantial defense against physical or electrical attacks against the entity itself. It is assumed the potential attacker has captured the entity and can disassemble it. Examples 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 use case 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 formal security certification scheme, such as those based on FIPS 140 [FIPS-140] or those based on Common Criteria [Common.Criteria]. See Section 3.21.¶

$$claims-set-claims //= (
    security-level-label =>
        security-level-cbor-type /
        security-level-json-type
)

security-level-cbor-type = &(
    unrestricted: 1,
    restricted: 2,
    secure-restricted: 3,
    hardware: 4
)

security-level-json-type =
    "unrestricted" /
    "restricted" /
    "secure-restricted" /
    "hardware"

3.12. Secure Boot Claim (secure-boot)

The value of true indicates secure boot is enabled. Secure boot is considered enabled when the firmware and operating system, are under control of the manufacturer of the entity identified in the OEMID claim described in Section 3.6. Control by the manufacturer of the firmware and the operating system may be by it being in ROM, being cryptographically authenticated, a combination of the two or similar.¶

$$claims-set-claims //= (secure-boot-label => bool)

3.13. Debug Status Claim (debug-status)

This applies to entity-wide or submodule-wide debug facilities of the entity 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 characterization assumes that debug facilities can be enabled and disabled in a dynamic way or be disabled in some permanent way 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-entity public keys.¶

As with all claims, the absence of the debug level claim means it is not reported. A conservative interpretation might assume the enabled state.¶

This claim is not extensible so as to provide a common interoperable description of debug status. 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.¶

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.¶

There is no inheritance of claims from a submodule to a superior module or vice versa. There is no assumption, requirement or guarantee that the target of a superior module encompasses the targets of submodules. Thus, every submodule must explicitly describe its own debug state. The receiver of an EAT MUST not assume that debug is turned off in a submodule because there is a claim indicating it is turned off in a superior module.¶

An entity may have multiple debug facilities. The use of plural in the description of the states refers to that, not to any aggregation or inheritance.¶

The architecture of some chips or devices may be such that a debug facility operates for the whole chip or device. If the EAT for such a chip includes submodules, then each submodule should independently report the status of the whole-chip or whole-device debug facility. This is the only way the receiver can know the debug status of the submodules since there is no inheritance.¶

$$claims-set-claims //=  (
    debug-status-label =>
        debug-status-cbor-type / debug-status-json-type
)

debug-status-cbor-type = &(
    enabled: 0,
    disabled: 1,
    disabled-since-boot: 2,
    disabled-permanently: 3,
    disabled-fully-and-permanently: 4
)

debug-status-json-type =
    "enabled" /
    "disabled" /
    "disabled-since-boot" /
    "disabled-permanently" /
    "disabled-fully-and-permanently"

3.14. 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 public 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 possession. Different EAT use cases may choose to associate further semantics. The key in the confirmation claim MUST be protected in the same way 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.¶

3.15. The Location Claim (location)

The location claim gives the location of the 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 entity is stationary, the heading is NaN (floating-point not-a-number). The speed is the horizontal component of the entity velocity in meters per second.¶

When encoding floating-point numbers half-precision SHOULD NOT be used. They usually do not provide enough precision for a geographic 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 location-related privacy considerations in Section 10.2.¶

$$claims-set-claims //= (location-label => location-type)

location-type = {
    latitude => number,
    longitude => number,
    ? altitude => number,
    ? accuracy => number,
    ? altitude-accuracy => number,
    ? heading => number,
    ? speed => number,
    ? timestamp => ~time-int,
    ? age => uint
}

latitude = 1 / "latitude"
longitude = 2 / "longitude"
altitude = 3 / "altitude"
accuracy = 4 / "accuracy"
altitude-accuracy = 5 / "altitude-accuracy"
heading = 6 / "heading"
speed = 7 / "speed"
timestamp = 8 / "timestamp"
age = 9 / "age"

3.16. The Uptime Claim (uptime)

The "uptime" claim MUST contain a value that represents the number of seconds that have elapsed since the entity or submod was last booted.¶

$$claims-set-claims //= (uptime-label => uint)

3.17. The Boot Odometer Claim (odometer)

The "odometer" claim contains a value that represents the number of times the entity or submod has been booted. Support for this claim requires a persistent storage on the device.¶

$$claims-set-claims //= (odometer-label => uint)

3.18. The Boot Seed Claim (boot-seed)

The Boot Seed claim MUST contain a random value created at system boot time that will allow differentiation of reports from different boot sessions.¶

This value is usually public. It is not a secret and MUST NOT be used for any purpose that a secret seed is needed, such as seeding a random number generator.¶

$$claims-set-claims //=  (boot-seed-label => bytes)

3.19. 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 requires 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 entity security state of the entity prior to provisioning.¶

4 - Certificate Issuance

Certification 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) application. More precisely, a PoP transaction is intended to provide to the recipient cryptographically-verifiable proof that the sender has possession of a key. This kind of attestation may be necceesary to verify the security state of the entity storing the private key used in a PoP application.¶

$$claims-set-claims //= (
    intended-use-label =>
        intended-use-cbor-type / intended-use-json-type
)

intended-use-cbor-type = &(
    generic: 1,
    registration: 2,
    provisioning: 3,
    csr: 4,
    pop: 5
)

intended-use-json-type =
    "generic" /
    "registration" /
    "provisioning" /
    "csr" /
    "pop"

3.20. The Profile Claim (profile)

See Section 7 for the detailed description of a profile.¶

A profile is identified by either a URL or an OID. Typically, the URI will reference a document describing the profile. An OID is just a unique identifier for the profile. It may exist anywhere in the OID tree. There is no requirement that the named document be publicly accessible. The primary purpose of the profile claim is to uniquely identify the profile even if it is a private profile.¶

The OID is always absolute and never relative. In CBOR tokens, the OID MUST be encoded according to [RFC9090] and the URI according to [RFC8949]. Both are unwrapped and thus not CBOR tags. In JSON tokens, the OID is a string of the form "X.X.X", and a URI is a normal URI string.¶

Note that this is named "eat_profile" for JWT and is distinct from the already registered "profile" claim in the JWT claims registry.¶

$$claims-set-claims //= (profile-label => ~uri / ~oid)

3.21. The DLOA (Digital Letter or Approval) Claim (dloas)

A DLOA (Digital Letter of Approval) [DLOA] is an XML document that describes a certification that an entity has received. Examples of certifications represented by a DLOA include those issued by Global Platform and those based on Common Criteria. The DLOA is unspecific to any particular certification type or those issued by any particular organization.¶

This claim is typically issued by a Verifier, not an Attester. When this claim is issued by a Verifier, it MUST be because the entity has received the certification in the DLOA.¶

This claim MAY contain more than one DLOA. If multiple DLOAs are present, it MUST be because the entity received all of the certifications.¶

DLOA XML documents are always fetched from a registrar that stores them. This claim contains several data items used to construct a URL for fetching the DLOA from the particular registrar.¶

This claim MUST be encoded as an array with either two or three elements. The first element MUST be the URI for the registrar. The second element MUST be a platform label indicating which platform was certified. If the DLOA applies to an application, then the third element is added which MUST be an application label. The method of constructing the registrar URI, platform label and possibly application label is specified in [DLOA].¶

$$claims-set-claims //= (
    dloas-label => [ + dloa-type ]
)

dloa-type = [
    dloa_registrar: ~uri
    dloa_platform_label: text
    ? dloa_application_label: text
]

3.22. The Software Manifests Claim (manifests)

This claim contains descriptions of software present on the entity. These manifests are installed on the entity when the software is installed or are created as part of the installation process. Installation is anything that adds software to the entity, possibly factory installation, the user installing elective applications and so on. The defining characteristic is they are created by the software manufacturer. The purpose of these claims in an EAT is to relay them without modification to the Verifier and possibly to the Relying Party.¶

Some manifests may be signed by their software manufacturer before they are put into this EAT claim. When such manifests are put into this claim, the manufacturer's signature SHOULD be included. For example, the manifest might be a CoSWID signed by the software manufacturer, in which case the full signed CoSWID should be put in this claim.¶

This claim allows multiple formats for the manifest. For example, the manifest may be a CBOR-format CoSWID, an XML-format SWID or other. Identification of the type of manifest is always by a CBOR tag. In many cases, for examples CoSWID, a tag will already be registered with IANA. If not, a tag MUST be registered. It can be in the first-come-first-served space which has minimal requirements for registration.¶

The claim is an array of one or more manifests. To facilitate hand off of the manifest to a decoding library, each manifest is contained in a byte string. This occurs for CBOR-format manifests as well as non-CBOR format manifests.¶

If a particular manifest type uses CBOR encoding, then the item in the array for it MUST be a byte string that contains a CBOR tag. The EAT decoder must decode the byte string and then the CBOR within it to find the tag number to identify the type of manifest. The contents of the byte string is then handed to the particular manifest processor for that type of manifest. CoSWID and SUIT manifest are examples of this.¶

If a particular manifest type does not use CBOR encoding, then the item in the array for it MUST be a CBOR tag that contains a byte string. The EAT decoder uses the tag to identify the processor for that type of manifest. The contents of the tag, the byte string, are handed to the manifest processor. Note that a byte string is used to contain the manifest whether it is a text based format or not. An example of this is an XML format ISO/IEC 19770 SWID.¶

It is not possible to describe the above requirements in CDDL, so the type for an individual manifest is any in the CDDL below. The above text sets the encoding requirement.¶

This claim allows for multiple manifests in one token since multiple software packages are likely to be present. The multiple manifests MAY be of multiple formats. In some cases EAT submodules may be used instead of the array structure in this claim for multiple manifests.¶

When the [CoSWID] format is used, it MUST be a payload CoSWID, not an evidence CoSWID.¶

$$claims-set-claims //= (
    manifests-label => manifests-type
)

manifests-type = [+ $$manifest-formats]

coswid-that-is-a-cbor-tag-xx = tagged-coswid<concise-swid-tag>

$$manifest-formats /= bytes .cbor coswid-that-is-a-cbor-tag-xx

3.23. The Software Evidence Claim (swevidence)

This claim contains descriptions, lists, evidence or measurements of the software that exists on the entity. The defining characteristic of this claim is that its contents are created by processes on the entity that inventory, measure or otherwise characterize the software on the entity. The contents of this claim do not originate from the software manufacturer.¶

This claim uses the same mechanism for identification of the type of the swevidence as is used for the type of the manifest in the manifests claim. It also uses the same byte string based mechanism for containing the claim and easing the hand off to a processing library. See the discussion above in the manifests claim.¶

When the [CoSWID] format is used, it MUST be evidence CoSWIDs, not payload CoSWIDS.¶

$$claims-set-claims //= (
    swevidence-label => swevidence-type
)

swevidence-type = [+ $$swevidence-formats]

coswid-that-is-a-cbor-tag = tagged-coswid<concise-swid-tag>
$$swevidence-formats /= bytes .cbor coswid-that-is-a-cbor-tag

3.24. The SW Measurement Results Claim (swresults)

This claims reports the outcome of the comparison of a measurement on some software to the expected Reference Values. It may report a successful comparison, failed comparison or other.¶

This claim MAY be generated by the Verifier and sent to the Relying Party. For example, it could be the results of the Verifier comparing the contents of the swevidence claim to Reference Values.¶

This claim MAY also be generated on the entity if the entity has the ability for one subsystem to measure another subsystem. For example, a TEE might have the ability to measure the software of the rich OS and may have the Reference Values for the rich OS.¶

Within an attestation target or submodule, multiple results can be reported. For example, it may be desirable to report the results for the kernel and each individual application separately.¶

For each software objective, the following can be reported. TODO: defined objective¶

$$claims-set-claims //= (swresults-label => [ + swresult-type ])

verification-result-cbor-type = &(
    verification-not-run: 1,
    verification-indeterminate: 2,
    verification-failed: 3,
    fully-verified: 4,
    partially-verified: 5,
)

verification-result-json-type =
    "verification-not-run" /
    "verification-indeterminate" /
    "verification-failed" /
    "fully-verified" /
    "partially-verified"


verification-objective-cbor-type = &(
    all: 1,
    firmware: 2,
    kernel: 3,
    privileged: 4,
    system-libs: 5,
    partial: 6,
)

verification-objective-json-type =
    "all" /
    "firmware" /
    "kernel" /
    "privileged" /
    "system-libs" /
    "partial"


swresult-type = [
    verification-system: tstr,
    objective: verification-objective-cbor-type /
        verification-objective-json-type,
    result: verification-result-cbor-type /
        verification-result-json-type,
    ? objective-name: tstr
]

3.25. Submodules (submods)

Some devices are complex, having many subsystems. A mobile phone is a good example. It may have several connectivity subsystems for communications (e.g., Wi-Fi and cellular). It may have subsystems for low-power audio and video playback. It may have multiple security-oriented subsystems like a TEE and a Secure Element.¶

The claims for a subsystem can be grouped together in a submodule or submod.¶

The submods are in a single map/object, one entry per submodule. There is only one submods map/object in a token. It is identified by its specific label. It is a peer to other claims, but it is not called a claim because it is a container for a claims set rather than an individual claim. This submods part of a token allows what might be called recursion. It allows claims sets inside of claims sets inside of claims sets...¶

Nested-Token =
    tstr / ; A JSON-encoded Nested-Token (see json-nested-token.cddl)
    bstr .cbor Tagged-CBOR-Token

Nested-Token = [
   type : "JWT" / "CBOR" / "UJCS" / "DEB",
   nested-token : JWT-Message /
                  B64URL-Tagged-CBOR-Token /
                  DEB-JSON-Message /
                  UJCS-Message
]


B64URL-Tagged-CBOR-Token = tstr .regexp "[A-Za-z0-9_=-]+"

$$claims-set-claims //= (submods-label => { + text => Submodule })

Submodule = Claims-Set / Nested-Token / Detached-Submodule-Digest

Detached-Submodule-Digest = [
   algorithm : int / text,
   digest : bstr
]

6.1. Identification Methods

Following is a list of possible methods of key identification. A specific attestation system may employ any one of these or one not listed here.¶

The following assumes Endorsements are X.509 certificates or equivalent and thus does not mention or define any identifier for Endorsements in other formats. If such an Endorsement format is created, new identifiers for them will also need to be created.¶

6.2. Other Considerations

In all cases there must be some way that the verification key is itself verified or determined to be trustworthy. The key identification itself is never enough. This will always be by some out-of-band mechanism that is not described here. For example, the Verifier may be configured with a root certificate or a master key by the Verifier system administrator.¶

Often an X.509 certificate or an Endorsement carries more than just the verification key. For example, an X.509 certificate might have key usage constraints and an Endorsement might have Reference Values. When this is the case, the key identifier must be either a protected header or in the payload such that it is cryptographically bound to the EAT. This is in line with the requirements in section 6 on Key Identification in JSON Web Signature [RFC7515].¶

7.1. Format of a Profile Document

A profile document doesn't have to be in any particular format. It may be simple text, something more formal or a combination.¶

In some cases CDDL may be created that replaces CDDL in this or other document to express some profile requirements. For example, to require the altitude data item in the location claim, CDDL can be written that replicates the location claim with the altitude no longer optional.¶

7.2. List of Profile Issues

The following is a list of EAT, CWT, UCCS, JWS, UJCS, COSE, JOSE and CBOR options that a profile should address.¶

8.1. Claims-Set and CDDL for CWT and JWT

CDDL was not used to define CWT or JWT. It was not available at the time.¶

This document defines CDDL for both CWT and JWT as well as UCCS. This document does not change the encoding or semantics of anything in a CWT or JWT.¶

A Claims-Set is the central data structure for EAT, CWT, JWT and UCCS. It holds all the claims and is the structure that is secured by signing or other means. It is not possible to define EAT, CWT, JWT or UCCS in CDDL without it. The CDDL definition of Claims-Set here is applicable to EAT, CWT, JWT and UCCS.¶

This document specifies how to encode a Claims-Set in CBOR or JSON.¶

With the exception of nested tokens and some other externally defined structures (e.g., SWIDs) an entire Claims-Set must be in encoded in either CBOR or JSON, never a mixture.¶

CDDL for the seven claims defined by [RFC8392] and [RFC7519] is included here.¶

8.2. Encoding Data Types

This makes use of the types defined in [RFC8610] Appendix D, Standard Prelude.¶

string-or-uri = tstr

time-int = #6.1(int)

8.3. CBOR Interoperability

CBOR allows data items to be serialized in more than one form. If the sender uses a form that the receiver can't decode, there will not be interoperability.¶

This specification gives no blanket requirements to narrow CBOR serialization for all uses of EAT. This allows individual uses to tailor serialization to the environment. It also may result in EAT implementations that don't interoperate.¶

One way to guarantee interoperability is to clearly specify CBOR serialization in a profile document. See Section 7 for a list of serialization issues that should be addressed.¶

EAT will be commonly used where the entity generating the attestation is constrained and the receiver/Verifier of the attestation is a capacious server. Following is a set of serialization requirements that work well for that use case and are guaranteed to interoperate. Use of this serialization is recommended where possible, but not required. An EAT profile may just reference the following section rather than spell out serialization details.¶

8.4. Collected Common CDDL

Claims-Set = {
    * $$claims-set-claims,
    * Claim-Label .feature "extended-label" => any
}

Claim-Label = int / text
string-or-uri = tstr

time-int = #6.1(int)
$$claims-set-claims //= (iss-label => text)
$$claims-set-claims //= (sub-label => text)
$$claims-set-claims //= (aud-label => text)
$$claims-set-claims //= (exp-label => ~time)
$$claims-set-claims //= (nbf-label => ~time)
$$claims-set-claims //= (iat-label => ~time)

$$claims-set-claims //=
    (nonce-label => nonce-type / [ 2* nonce-type ])

nonce-type = bstr .size (8..64)
$$claims-set-claims //= (ueid-label => ueid-type)

ueid-type = bstr .size (7..33)
$$claims-set-claims //= (sueids-label => sueids-type)

sueids-type = {
    + tstr => ueid-type
}
oemid-pen = int

oemid-ieee = bstr .size 3

oemid-random = bstr .size 16


$$claims-set-claims //= (
    oemid-label =>
        oemid-random / oemid-ieee / oemid-pen
)
$$claims-set-claims //=  (
    hardware-version-label => hardware-version-type
)

hardware-version-type = [
    version:  tstr,
    scheme:  $version-scheme
]
hardware-model-type = bytes .size (1..32)

$$claims-set-claims //= (
    hardware-model-label => hardware-model-type
)
$$claims-set-claims //= ( sw-name-label => tstr )
$$claims-set-claims //= (sw-version-label => sw-version-type)

sw-version-type = [
    version:  tstr,
    scheme:  $version-scheme ; As defined by CoSWID
]
$$claims-set-claims //= (
    security-level-label =>
        security-level-cbor-type /
        security-level-json-type
)

security-level-cbor-type = &(
    unrestricted: 1,
    restricted: 2,
    secure-restricted: 3,
    hardware: 4
)

security-level-json-type =
    "unrestricted" /
    "restricted" /
    "secure-restricted" /
    "hardware"
$$claims-set-claims //= (secure-boot-label => bool)
$$claims-set-claims //=  (
    debug-status-label =>
        debug-status-cbor-type / debug-status-json-type
)

debug-status-cbor-type = &(
    enabled: 0,
    disabled: 1,
    disabled-since-boot: 2,
    disabled-permanently: 3,
    disabled-fully-and-permanently: 4
)

debug-status-json-type =
    "enabled" /
    "disabled" /
    "disabled-since-boot" /
    "disabled-permanently" /
    "disabled-fully-and-permanently"
$$claims-set-claims //= (location-label => location-type)

location-type = {
    latitude => number,
    longitude => number,
    ? altitude => number,
    ? accuracy => number,
    ? altitude-accuracy => number,
    ? heading => number,
    ? speed => number,
    ? timestamp => ~time-int,
    ? age => uint
}

latitude = 1 / "latitude"
longitude = 2 / "longitude"
altitude = 3 / "altitude"
accuracy = 4 / "accuracy"
altitude-accuracy = 5 / "altitude-accuracy"
heading = 6 / "heading"
speed = 7 / "speed"
timestamp = 8 / "timestamp"
age = 9 / "age"
$$claims-set-claims //= (uptime-label => uint)
$$claims-set-claims //=  (boot-seed-label => bytes)
$$claims-set-claims //= (odometer-label => uint)
$$claims-set-claims //= (
    intended-use-label =>
        intended-use-cbor-type / intended-use-json-type
)

intended-use-cbor-type = &(
    generic: 1,
    registration: 2,
    provisioning: 3,
    csr: 4,
    pop: 5
)

intended-use-json-type =
    "generic" /
    "registration" /
    "provisioning" /
    "csr" /
    "pop"
$$claims-set-claims //= (
    dloas-label => [ + dloa-type ]
)

dloa-type = [
    dloa_registrar: ~uri
    dloa_platform_label: text
    ? dloa_application_label: text
]
$$claims-set-claims //= (profile-label => ~uri / ~oid)
$$claims-set-claims //= (
    manifests-label => manifests-type
)

manifests-type = [+ $$manifest-formats]

coswid-that-is-a-cbor-tag-xx = tagged-coswid<concise-swid-tag>

$$manifest-formats /= bytes .cbor coswid-that-is-a-cbor-tag-xx$$claims-set-claims //= (
    swevidence-label => swevidence-type
)

swevidence-type = [+ $$swevidence-formats]

coswid-that-is-a-cbor-tag = tagged-coswid<concise-swid-tag>
$$swevidence-formats /= bytes .cbor coswid-that-is-a-cbor-tag
$$claims-set-claims //= (swresults-label => [ + swresult-type ])

verification-result-cbor-type = &(
    verification-not-run: 1,
    verification-indeterminate: 2,
    verification-failed: 3,
    fully-verified: 4,
    partially-verified: 5,
)

verification-result-json-type =
    "verification-not-run" /
    "verification-indeterminate" /
    "verification-failed" /
    "fully-verified" /
    "partially-verified"


verification-objective-cbor-type = &(
    all: 1,
    firmware: 2,
    kernel: 3,
    privileged: 4,
    system-libs: 5,
    partial: 6,
)

verification-objective-json-type =
    "all" /
    "firmware" /
    "kernel" /
    "privileged" /
    "system-libs" /
    "partial"


swresult-type = [
    verification-system: tstr,
    objective: verification-objective-cbor-type /
        verification-objective-json-type,
    result: verification-result-cbor-type /
        verification-result-json-type,
    ? objective-name: tstr
]
$$claims-set-claims //= (submods-label => { + text => Submodule })

Submodule = Claims-Set / Nested-Token / Detached-Submodule-Digest

Detached-Submodule-Digest = [
   algorithm : int / text,
   digest : bstr
]
Detached-EAT-Bundle = [
    main-token : Nested-Token,
    detached-claims-sets: {
        + tstr => cbor-wrapped-claims-set / json-wrapped-claims-set
    }
]


json-wrapped-claims-set = tstr .regexp "[A-Za-z0-9_=-]+"


cbor-wrapped-claims-set = bstr .cbor Claims-Set

8.5. Collected CDDL for CBOR

CBOR-Token = Tagged-CBOR-Token / Untagged-CBOR-Token


Tagged-CBOR-Token  = CWT-Tagged-Message
Tagged-CBOR-Token /= UCCS-Tagged-Message
Tagged-CBOR-Token /= DEB-Tagged-Message


Untagged-CBOR-Token  = CWT-Untagged-Message
Untagged-CBOR-Token /= UCCS-Untagged-Message
Untagged-CBOR-Token /= DEB-Untagged-Message


CWT-Tagged-Message = COSE_Tagged_Message
CWT-Untagged-Message = COSE_Untagged_Message


UCCS-Message = UCCS-Tagged-Message / UCCS-Untagged-Message

UCCS-Tagged-Message = #6.601(UCCS-Untagged-Message)

UCCS-Untagged-Message = Claims-Set


DEB-Tagged-Message = #6.602(DEB-Untagged-Message)

DEB-Untagged-Message = Detached-EAT-Bundle


Nested-Token =
    tstr / ; A JSON-encoded Nested-Token (see json-nested-token.cddl)
    bstr .cbor Tagged-CBOR-Token


iss-label = 1
sub-label = 2
aud-label = 3
exp-label = 4
nbf-label = 5
iat-label = 6
cti-label = 7nonce-label = 10
ueid-label = 256
sueids-label = 257
oemid-label = 258
hardware-model-label = 259
hardware-version-label = 260
secure-boot-label = 262
debug-status-label = 263
location-label = 264
profile-label = 265
submods-label = 266
security-level-label = <TBD>
uptime-label = <TBD>
boot-seed-label = <TB>
odometer-label = <TBD>
intended-use-label = <TBD>
dloas-label = <TBD>
sw-name-label = <TBD>
sw-version-label = <TBD>
manifests-label = <TBD>
swevidence-label = <TBD>
swresults-label = <TBD>

8.6. Collected CDDL for JSON

JWT-Message = text .regexp [A-Za-z0-9_=-]+\.[A-Za-z0-9_=-]+\.[A-Za-z0-9_=-]+

UJCS-Message = Claims-Set

Nested-Token = [
   type : "JWT" / "CBOR" / "UJCS" / "DEB",
   nested-token : JWT-Message /
                  B64URL-Tagged-CBOR-Token /
                  DEB-JSON-Message /
                  UJCS-Message
]


B64URL-Tagged-CBOR-Token = tstr .regexp "[A-Za-z0-9_=-]+"
iss-label = "iss"
sub-label = "sub"
aud-label = "aud"
exp-label = "exp"
nbf-label = "nbf"
iat-label = "iat"
cti-label = "cti"nonce-label /= "nonce"


ueid-label /= "ueid"
sueids-label /= "sueids"
oemid-label /= "oemid"
hardware-model-label /= "hwmodel"
hardware-version-label /= "hwversion"
security-level-label /= "seclevel"
secure-boot-label /= "secboot"
debug-status-label /= "dbgstat"
location-label /= "location"
profile-label /= "eat-profile"
uptime-label /= "uptime"
boot-seed-label /= "bootseed"
odometer-label /= "odometer"
intended-use-label /= "intuse"
dloas-label /= "dloas"
sw-name-label /= "swname"
sw-version-label /= "swversion"
manifests-label /= "manifests"
swevidence-label /= "swevidence"
swresults-label /= "swresults"
submods-label /= "submods"


latitude /= "lat"
longitude /= "long"
altitude /= "alt"
accuracy /= "accry"
altitude-accuracy /= "alt-accry"
heading /= "heading"
speed /= "speed"

9.1. Reuse of CBOR and JSON Web Token (CWT and JWT) Claims Registries

Claims defined for EAT are compatible with those of CWT and JWT so the CWT and JWT Claims Registries, [IANA.CWT.Claims] and [IANA.JWT.Claims], are re used. No new IANA registry is created.¶

All EAT claims defined in this document are placed in both registries. All new EAT claims defined subsequently should be placed in both registries.¶

9.2. Claim Characteristics

The following is design guidance for creating new EAT claims, particularly those to be registered with IANA.¶

Much of this guidance is generic and could also be considered when designing new CWT or JWT claims.¶

9.3. Claims Registered by This Document

This specification adds the following values to the "JSON Web Token Claims" registry established by [RFC7519] and the "CBOR Web Token Claims Registry" established by [RFC8392]. Each entry below is an addition to both registries (except for the nonce claim which is already registered for JWT, but not registered for CWT).¶

The "Claim Description", "Change Controller" and "Specification Documents" are common and equivalent for the JWT and CWT registries. The "Claim Key" and "Claim Value Types(s)" are for the CWT registry only. The "Claim Name" is as defined for the CWT registry, not the JWT registry. The "JWT Claim Name" is equivalent to the "Claim Name" in the JWT registry.¶

10.1. UEID and SUEID Privacy Considerations

A UEID is usually not privacy-preserving. Any set of Relying Parties that receives tokens that happen to be from a particular entity will be able to know the tokens are all from the same entity and be able to track it.¶

Thus, in many usage situations UEID violates governmental privacy regulation. In other usage situations a UEID will 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 have a UEID for these reasons.¶

An SUEID is also usually not privacy-preserving. In some cases it may have fewer privacy issues than a UEID depending on when and how and when it is generated.¶

There are several strategies that can be used to still be able to put UEIDs and SUEIDs in tokens:¶

• The entity obtains explicit permission from the user of the entity to use the UEID/SUEID. This may be through a prompt. It may also be through a license agreement. For example, agreements for some online banking and brokerage services might already cover use of a UEID/SUEID.¶
• The UEID/SUEID is used only in a particular context or particular use case. It is used only by one Relying Party.¶
• The entity authenticates the Relying Party and generates a derived UEID/SUEID just for that particular Relying Party. For example, the Relying Party could prove their identity cryptographically to the entity, then the entity generates a UEID just for that Relying Party by hashing a proofed Relying Party ID with the main entity UEID/SUEID.¶

Note that some of these privacy preservation strategies result in multiple UEIDs and SUEIDs per entity. Each UEID/SUEID is used in a different context, use case or system on the entity. However, from the view of the Relying Party, there is just one UEID and it is still globally universal across manufacturers.¶

10.2. 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 entity generating the attestation. For example, many mobile phones prompt the user for permission when before sending location data.¶

10.3. Replay Protection and Privacy

EAT offers 2 primary mechanisms for token replay protection (also sometimes known as token "freshness"): the cti/jti claim and the nonce claim. The cti/jti claim in a CWT/JWT is a field that may be optionally included in the EAT and is in general derived on the same device in which the entity is instantiated. The nonce claim is based on a value that is usually derived remotely (outside of the entity). These claims can be used to extract and convey personally-identifying information either inadvertently or by intention. For instance, an implementor may choose a cti that is equivalent to a username associated with the device (e.g., account login). If the token is inspected by a 3rd-party then this information could be used to identify the source of the token or an account associated with the token (e.g., if the account name is used to derive the nonce). In order to avoid the conveyance of privacy-related information in either the cti/jti or nonce claims, these fields should be derived using a salt that originates from a true and reliable random number generator or any other source of randomness that would still meet the target system requirements for replay protection.¶

11.1. Key Provisioning

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. In some instances, the manufacturer of the entity may create the key material separately and provision the key material in the entity itself. The manfuacturer of any entity that is capable of producing an EAT should take care to ensure that any private key material be suitably protected prior to provisioning the key material in the entity itself. This can require creation of key material in an enclave (see [RFC4949] for definition of "enclave"), secure transmission of the key material from the enclave to the entity using an appropriate protocol, and persistence of the private key material in some form of secure storage to which (preferably) only the entity has access.¶

11.2. Transport Security

As stated in Section 8 of [RFC8392], "The security of the CWT relies upon on the protections offered by COSE". Similar considerations 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 an entity that may not support the same type of transport security as the consumer of the EAT, intermediaries may be required to bridge communications between the entity and consumer. As a result, it is RECOMMENDED that both the consumer create a nonce, and the entity leverage the nonce along with COSE mechanisms for encryption and/or signing to create the EAT.¶

Similar considerations apply to the use of EAT as a JWT. Although the security of a JWT leverages the JSON Web Encryption (JWE) and JSON Web Signature (JWS) specifications, it is still recommended to make use of the EAT nonce.¶

11.3. Multiple EAT Consumers

In many cases, more than one EAT consumer may be required to fully verify the entity attestation. Examples include individual consumers for nested EATs, or consumers for individual claims with an EAT. When multiple consumers are required for verification of an EAT, it is important to minimize information exposure to each consumer. In addition, the communication between multiple consumers should be secure.¶

For instance, consider the example of an encrypted and signed EAT with multiple claims. A consumer may receive the EAT (denoted as the "receiving consumer"), decrypt its payload, verify its signature, but then pass specific subsets of claims to other consumers for evaluation ("downstream consumers"). Since any COSE encryption will be removed by the receiving consumer, the communication of claim subsets to any downstream consumer should leverage a secure protocol (e.g.one that uses transport-layer security, i.e. TLS),¶

However, assume the EAT of the previous example is hierarchical and each claim subset for a downstream consumer is created in the form of a nested EAT. Then transport security between the receiving and downstream consumers is not strictly required. Nevertheless, downstream consumers of a nested EAT should provide a nonce unique to the EAT they are consuming.¶

A.1. Simple TEE Attestation

This is a simple attestation of a TEE that includes a manifest that is a payload CoSWID to describe the TEE's software.¶

/ This is a UCCS EAT that describes a simple TEE. /

601({
    / nonce /           10: h'948f8860d13a463e',
    / security-level / 261: 3, / secure-restricted /
    / secure-boot /    262: true,
    / debug-status /   263: 2, / disabled-since-boot /
    / manfests /       273: [
                               / This is byte-string wrapped      /
                               / payload CoSWID. It gives the TEE /
                               / software name, the version and   /
                               / the  name of the file it is in.  /
                               h' da53574944a60064336132340c01016b
                                  41636d6520544545204f530d65332e31
                                  2e340282a2181f6b41636d6520544545
                                  204f53182101a2181f6b41636d652054
                                  4545204f5318210206a111a118186e61
                                  636d655f7465655f332e657865'
                        ]
})

/ A payload CoSWID created by the SW vendor. All this really does /
/ is name the TEE SW, its version and lists the one file that     /
/ makes up the TEE. /

1398229316({
    / Unique CoSWID ID /    0: "3a24",
    / tag-version /        12: 1,
    / software-name /       1: "Acme TEE OS",
    / software-version /   13: "3.1.4",
    / entity /              2: [
                                   {
        / entity-name /                31: "Acme TEE OS",
        / role        /                33: 1 / tag-creator /
                                   },
                                   {
        / entity-name /                31: "Acme TEE OS",
        / role        /                33: 2 / software-creator /
                                   }
                               ],
    / payload /                6: {
        / ...file /                17: {
            / ...fs-name /             24: "acme_tee_3.exe"
                                   }
                               }
})

A.2. Submodules for Board and Device

/ This example shows use of submodules to give information  /
/ about the chip, board and overall device.                 /
/                                                           /
/ The main attestation is associated with the chip with the /
/ CPU and running the main OS. It is what has the keys and  /
/ produces the token.                                       /
/                                                           /
/ The board is made by a different vendor than the chip.    /
/ Perhaps it is some generic IoT board.                     /
/                                                           /
/ The device is some specific appliance that is made by a   /
/ different vendor than either the chip or the board.       /
/                                                           /
/ Here the board and device submodules aren't the typical   /
/ target environments as described by the RATS architecture /
/ document, but they are a valid use of submodules.         /

{
    / nonce /           10: h'948f8860d13a463e8e',
    / UEID /           256: h'0198f50a4ff6c05861c8860d13a638ea',
    / HW OEM ID /      258: h'894823', / IEEE OUI format OEM ID /
    / HW Model ID /    259: h'549dcecc8b987c737b44e40f7c635ce8'
                              / Hash of chip model name /,
    / HW Version /     260: ["1.3.4", 1], / Multipartnumeric version /
    / SW Name /        271: "Acme OS",
    / SW Version /     272: ["3.5.5", 1],
    / secure-boot /    262: true,
    / debug-status /   263: 3, / permanent-disable  /
    / timestamp (iat) /  6: 1526542894,
    / security-level / 261: 3, / secure restricted OS /
    / submods / 266: {
        / A submodule to hold some claims about the circuit board /
        "board" :  {
            / HW OEM ID /   258: h'9bef8787eba13e2c8f6e7cb4b1f4619a',
            / HW Model ID / 259: h'ee80f5a66c1fb9742999a8fdab930893'
                                      / Hash of board module name /,
            / HW Version /  260: ["2.0a", 2] / multipartnumeric+suffix /
        },

        / A submodule to hold claims about the overall device /
        "device" :  {
            / HW OEM ID /   258: 61234, / PEN Format OEM ID /
            / HW Version /  260: ["4012345123456", 5] / EAN-13 format (barcode) /
        }
    }
}

A.3. EAT Produced by Attestation Hardware Block

/ This is an example of a token produced by a HW block            /
/ purpose-built for attestation.  Only the nonce claim changes    /
/ from one attestation to the next as the rest  either come       /
/ directly from the hardware or from one-time-programmable memory /
/ (e.g. a fuse). 47 bytes encoded in CBOR (8 byte nonce, 16 byte  /
/ UEID). /

601({
    / nonce /           10: h'948f8860d13a463e',
    / UEID /           256: h'0198f50a4ff6c05861c8860d13a638ea',
    / OEMID /          258: 64242, / Private Enterprise Number /
    / security-level / 261: 4, / hardware level security /
    / secure-boot /    262: true,
    / debug-status /   263: 3, / disabled-permanently /
    / HW version /     260: [ "3.1", 1 ] / Type is multipartnumeric /
})

A.4. Detached EAT Bundle

In this DEB main token is produced by a HW attestation block. The detached Claims-Set is produced by a TEE and is largely identical to the Simple TEE examples above. The TEE digests its Claims-Set and feeds that digest to the HW block.¶

In a better example the attestation produced by the HW block would be a CWT and thus signed and secured by the HW block. Since the signature covers the digest from the TEE that Claims-Set is also secured.¶

The DEB itself can be assembled by untrusted SW.¶

/ This is a detached EAT bundle (DEB) tag.  /

602([

    / First part is a full EAT token with claims like nonce and /
    / UEID. Most importantly, it includes a submodule that is a /
    / detached digest which is the hash of the "TEE" claims set /
    / in the next section.                                      /
    /                                                           /
    / This token here is in UCCS format (unsigned). In a more   /
    / realistic example, it would be a signed CWT.              /
    h'd90259a80a48948f8860d13a463e190100500198
    f50a4ff6c05861c8860d13a638ea19010219faf2
    19010504190106f5190107031901048263332e31
    0119010aa163544545822f5820e5cf95fd24fab7
    1446742dd58d43dae178e55fe2b94291a9291082
    ffc2635a0b',
    {
       / A CBOR-encoded byte-string wrapped EAT claims-set. It /
       / contains claims suitable for a TEE                    /
       "TEE" : h'a50a48948f8860d13a463e19010503190106f519
                 01070219011181585dda53574944a60064336132
                 340c01016b41636d6520544545204f530d65332e
                 312e340282a2181f6b41636d6520544545204f53
                 182101a2181f6b41636d6520544545204f531821
                 0206a111a118186e61636d655f7465655f332e65
                 7865'
    }
 ])

/ This example contains submodule that is a detached digest,   /
/ which is the hash of a Claims-Set convey outside this token. /
/ Other than that is is the other example of a token from an   /
/ attestation HW block                                         /

601({
    / nonce /           10: h'948f8860d13a463e',
    / UEID /           256: h'0198f50a4ff6c05861c8860d13a638ea',
    / OEMID /          258: 64242, / Private Enterprise Number /
    / security-level / 261: 4, / hardware level security /
    / secure-boot /    262: true,
    / debug-status /   263: 3, / disabled-permanently /
    / hw version /     260: [ "3.1", 1 ], / multipartnumeric /
    / submods/         266: {
                                "TEE": [ / detached digest submod /
                                    -16, / SHA-256 /
                                    h'e5cf95fd24fab7144674
                                      2dd58d43dae178e55fe2
                                      b94291a9291082ffc2635
                                      a0b'
                                ]
                            }
})

A.5. Key / Key Store Attestation

/ This is an attestation of a public key and the key store     /
/ implementation that protects and manages it. The key store   /
/ implementation is in a security-oriented execution           /
/ environment separate from the high-level OS, for example a   /
/ TEE. The key store is the Attester.                          /
/                                                              /
/ There is some attestation of the high-level OS, just version /
/ and boot & debug status. It is a Claims-Set submodule because/
/ it has lower security level than the key store. The key      /
/ store's implementation has access to info about the HLOS, so /
/ it is able to include it.                                    /
/                                                              /
/ A key and an indication of the user authentication given to  /
/ allow access to the key is given. The labels for these are   /
/ in the private space since this is just a hypothetical       /
/ example, not part of a standard protocol.                    /
/                                                              /
/ This is similar to Android Key Attestation.                  /


601({
    / nonce /           10: h'948f8860d13a463e',
    / security-level / 261: 3, / secure-restricted /
    / secure-boot /    262: true,
    / debug-status /   263: 2, / disabled-since-boot /
    / manifests /      273: [
                                h'da53574944a600683762623334383766
                                  0c000169436172626f6e6974650d6331
                                  2e320e0102a2181f75496e6475737472
                                  69616c204175746f6d6174696f6e1821
                                  02'
                                 / Above is an encoded CoSWID     /
                                 / with the following data        /
                                 /   SW Name: "Carbonite"         /
                                 /   SW Vers: "1.2"               /
                                 /   SW Creator:                  /
                                 /      "Industrial Automation"   /
                            ],
    / expiration /       4: 1634324274, / 2021-10-15T18:57:54Z /
    / creation time /    6: 1634317080, / 2021-10-15T16:58:00Z /
                   -80000 : "fingerprint",
                   -80001 : { / The key -- A COSE_Key  /
                / kty /       1: 2, / EC2, eliptic curve with x & y /
                / kid /       2: h'36675c206f96236c3f51f54637b94ced',
                / curve /    -1: 2, / curve is P-256 /
                / x-coord /  -2: h'65eda5a12577c2bae829437fe338701a
                                   10aaa375e1bb5b5de108de439c08551d',
                / y-coord /  -3: h'1e52ed75701163f7f9e40ddf9f341b3d
                                   c9ba860af7e0ca7ca7e9eecd0084d19c'
             },

    / submods /        266 : {
                           "HLOS" : { / submod for high-level OS /
         / nonce /             10: h'948f8860d13a463e',
           / security-level / 261: 1, / unrestricted /
           / secure-boot /    262: true,
           / manifests /      273: [
                                    h'da53574944a600687337
                                      6537346b78380c000168
                                      44726f6964204f530d65
                                      52322e44320e0302a218
                                      1F75496E647573747269
                                      616c204175746f6d6174
                                      696f6e182102'
                                     / Above is an encoded CoSWID /
                                     / with the following data:   /
                                     /   SW Name: "Droid OS"      /
                                     /   SW Vers: "R2.D2"         /
                                     /   SW Creator:              /
                                     /     "Industrial Automation"/
                               ]
                           }
                       }
})

A.6. SW Measurements of an IoT Device

This is a simple token that might be for and IoT device. It includes CoSWID format measurments of the SW. The CoSWID is in byte-string wrapped in the token and also shown in diagnostic form.¶

/ This EAT UCCS is for an IoT device with a TEE. The attestation   /
/ is produced by the TEE. There is a submodule for the IoT OS (the /
/ main OS of the IoT device that is not as secure as the TEE). The /
/ submodule contains claims for the IoT OS. The TEE also measures  /
/ the IoT OS and puts the measurements in the submodule.           /

601({
    / nonce /           10: h'948f8860d13a463e',
    / security-level / 261: 3, / secure-restricted /
    / secure-boot /    262: true,
    / debug-status /   263: 2, / disabled-since-boot /
    / OEMID /          258: h'8945ad', / IEEE CID based /
    / UEID /           256: h'0198f50a4ff6c05861c8860d13a638ea',
    / sumods /         266: {
                            "OS" : {
        / security-level /     261: 2, / restricted /
        / secure-boot /        262: true,
        / debug-status /       263: 2, / disabled-since-boot /
        / swevidence /         274: [
                                    / This is a byte-string wrapped /
                                    / evidence CoSWID. It has       /
                                    / hashes of the main files of   /
                                    / the IoT OS.  /
                                    h'da53574944a600663463613234350c
                                      17016d41636d6520522d496f542d4f
                                      530d65332e312e3402a2181f724163
                                      6d6520426173652041747465737465
                                      7218210103a11183a318187161636d
                                      655f725f696f745f6f732e65786514
                                      1a0044b349078201582005f6b327c1
                                      73b4192bd2c3ec248a292215eab456
                                      611bf7a783e25c1782479905a31818
                                      6d7265736f75726365732e72736314
                                      1a000c38b10782015820c142b9aba4
                                      280c4bb8c75f716a43c99526694caa
                                      be529571f5569bb7dc542f98a31818
                                      6a636f6d6d6f6e2e6c6962141a0023
                                      3d3b0782015820a6a9dcdfb3884da5
                                      f884e4e1e8e8629958c2dbc7027414
                                      43a913e34de9333be6'
                                ]
                            }
                        }
})

/ An evidence CoSWID created for the "Acme R-IoT-OS" created by /
/ the "Acme Base Attester" (both fictious names).  It provides  /
/ measurements of the SW (other than the attester SW) on the    /
/ device. /

1398229316({
    / Unique CoSWID ID /    0: "4ca245",
    / tag-version /        12: 23, / Attester-maintained counter /
    / software-name /       1: "Acme R-IoT-OS",
    / software-version /   13: "3.1.4",
    / entity /              2: {
        / entity-name /        31: "Acme Base Attester",
        / role        /        33: 1 / tag-creator /
                            },
    / evidence /            3: {
        / ...file /             17: [
                                    {
            / ...fs-name /              24: "acme_r_iot_os.exe",
            / ...size    /              20: 4502345,
            / ...hash    /               7: [
                                             1, / SHA-256 /
                                             h'05f6b327c173b419
                                               2bd2c3ec248a2922
                                               15eab456611bf7a7
                                               83e25c1782479905'
                                         ]
                                    },
                                    {
            / ...fs-name /              24: "resources.rsc",
            / ...size    /              20: 800945,
            / ...hash    /               7: [
                                              1, / SHA-256 /
                                             h'c142b9aba4280c4b
                                               b8c75f716a43c995
                                               26694caabe529571
                                               f5569bb7dc542f98'
                                         ]
                                    },
                                    {
            / ...fs-name /              24: "common.lib",
            / ...size    /              20: 2309435,
            / ...hash    /               7: [
                                             1, / SHA-256 /
                                             h'a6a9dcdfb3884da5
                                               f884e4e1e8e86299
                                               58c2dbc702741443
                                               a913e34de9333be6'
                                         ]
                                    }
                                ]
                            }
})

A.7. Attestation Results in JSON format

This is a UJCS format token that might be the output of a Verifier that evaluated the IoT Attestation example immediately above.¶

This particular Verifier knows enough about the TEE Attester to be able to pass claims like security level directly through to the Relying Party. The Verifier also knows the Reference Values for the measured SW components and is able to check them. It informs the Relying Party that they were correct in the swresults claim. "Trustus Verifications" is the name of the services that verifies the SW component measurements.¶

This UJCS is identical to JSON-encoded Claims-Set that could be a JWT payload.¶

{
    "nonce" : "lI+IYNE6Rj4=",
    "seclevel" : "secure-restricted",
    "secboot" : true,
    "dbgstat" : "disabled-since-boot",
    "OEMID" : "iUWt",
    "UEID" : "AZj1Ck/2wFhhyIYNE6Y4",
    "submods" : {
        "seclevel" : "restricted",
        "secboot" : true,
        "dbgstat" : "disabled-since-boot",
        "swname" : "Acme R-IoT-OS",
        "sw-version" : [
            "3.1.4"
        ],
        "swresults" : [
            [
                "Trustus Verifications",
                "all",
                "fully-verified"
            ]
       ]
}

B.1. Collision Probability

This calculation is to determine the probability of a collision of UEIDs given the total possible entity population and the number of entities in a particular entity management database.¶

Three different sized databases are considered. The number of devices per person roughly models non-personal devices such as traffic lights, devices in stores they shop in, facilities they work in and so on, even considering individual light bulbs. A device may have individually attested subsystems, for example parts of a car or a mobile phone. It is assumed that the largest database will have at most 10% of the world's population of devices. Note that databases that handle more than a trillion records exist today.¶

The trillion-record database size models an easy-to-imagine reality over the next decades. The quadrillion-record database is roughly at the limit of what is imaginable and should probably be accommodated. The 100 quadrillion datadbase is highly speculative perhaps involving nanorobots for every person, livestock animal and domesticated bird. It is included to round out the analysis.¶

Note that the items counted here certainly do not have IP address and are not individually connected to the network. They may be connected to internal buses, via serial links, Bluetooth and so on. This is not the same problem as sizing IP addresses.¶

This is conceptually similar to the Birthday Problem where m is the number of possible birthdays, always 365, and k is the number of people. It is also conceptually similar to the Birthday Attack where collisions of the output of hash functions are considered.¶

The proper formula for the collision calculation is¶

   p = 1 - e^{-k^2/(2n)}

   p   Collision Probability
   n   Total possible population
   k   Actual population

However, for the very large values involved here, this formula requires floating point precision higher than commonly available in calculators and SW so this simple approximation is used. See [BirthdayAttack].¶

   p = k^2 / 2n

For this calculation:¶

   p  Collision Probability
   n  Total population based on number of bits in UEID
   k  Population in a database

Next, to calculate the probability of a collision occurring in one year's operation of a database, it is assumed that the database size is in a steady state and that 10% of the database changes per year. For example, a trillion record database would have 100 billion states per year. Each of those states has the above calculated probability of a collision.¶

This assumption is a worst-case since it assumes that each state of the database is completely independent from the previous state. In reality this is unlikely as state changes will be the addition or deletion of a few records.¶

The following tables gives the time interval until there is a probability of a collision based on there being one tenth the number of states per year as the number of records in the database.¶

  t = 1 / ((k / 10) * p)

  t  Time until a collision
  p  Collision probability for UEID size
  k  Database size

Clearly, 128 bits is enough for the near future thus the requirement that UEIDs be a minimum of 128 bits.¶

There is no requirement for 256 bits today as quadrillion-record databases are not expected in the near future and because this time-to-collision calculation is a very worst case. A future update of the standard may increase the requirement to 256 bits, so there is a requirement that implementations be able to receive 256-bit UEIDs.¶

B.2. No Use of UUID

A UEID is not a UUID [RFC4122] by conscious choice for the following reasons.¶

UUIDs are limited to 128 bits which may not be enough for some future use cases.¶

Today, cryptographic-quality random numbers are available from common CPUs and hardware. This hardware was introduced between 2010 and 2015. Operating systems and cryptographic libraries give access to this hardware. Consequently, there is little need for implementations to construct such random values from multiple sources on their own.¶

Version 4 UUIDs do allow for use of such cryptographic-quality random numbers, but do so by mapping into the overall UUID structure of time and clock values. This structure is of no value here yet adds complexity. It also slightly reduces the number of actual bits with entropy.¶

UUIDs seem to have been designed for scenarios where the implementor does not have full control over the environment and uniqueness has to be constructed from identifiers at hand. UEID takes the view that hardware, software and/or manufacturing process directly implement UEID in a simple and direct way. It takes the view that cryptographic quality random number generators are readily available as they are implemented in commonly used CPU hardware.¶

C.1. DevID Used With EAT

As just described, EAT defines a network protocol and [IEEE.802.1AR] doesn't. Vice versa, EAT doesn't define a an device implementation and DevID does.¶

Hence, EAT can be the network protocol that a DevID is used with. The DevID secret becomes the attestation key used to sign EATs. The DevID and its certificate chain become the Endorsement sent to the Verifier.¶

In this case the EAT and the DevID are likely to both provide a device identifier (e.g. a serial number). In the EAT it is the UEID (or SUEID). In the DevID (used as an endorsement), it is a device serial number included in the subject field of the DevID certificate. It is probably a good idea in this use for them to be the same serial number or for the UEID to be a hash of the DevID serial number.¶

C.2. How EAT Provides an Equivalent Secure Device Identity

The UEID, SUEID and other claims like OEM ID are equivalent to the secure device identity put into the subject field of a DevID certificate. These EAT claims can represent all the same fields and values that can be put in a DevID certificate subject. EAT explicitly and carefully defines a variety of useful claims.¶

EAT secures the conveyance of these claims by having them signed on the device by the attestation key when the EAT is generated. EAT also signs the nonce that gives freshness at this time. Since these claims are signed for every EAT generated, they can include things that vary over time like GPS location.¶

DevID secures the device identity fields by having them signed by the manufacturer of the device sign them into a certificate. That certificate is created once during the manufacturing of the device and never changes so the fields cannot change.¶

So in one case the signing of the identity happens on the device and the other in a manufacturing facility, but in both cases the signing of the nonce that proves the binding to the actual device happens on the device.¶

While EAT does not specify how the signing keys, signature process and storage of the identity values should be secured against attack, an EAT implementation may have equal defenses against attack. One reason EAT uses CBOR is because it is simple enough that a basic EAT implementation can be constructed entirely in hardware. This allows EAT to be implemented with the strongest defenses possible.¶

C.3. An X.509 Format EAT

It is possible to define a way to encode EAT claims in an X.509 certificate. For example, the EAT claims might be mapped to X.509 v3 extensions. It is even possible to stuff a whole CBOR-encoded unsigned EAT token into a X.509 certificate.¶

If that X.509 certificate is an IDevID or LDevID, this becomes another way to use EAT and DevID together.¶

Note that the DevID must still be used with an authentication protocol that has a nonce or equivalent. The EAT here is not being used as the protocol to interact with the rely party.¶

C.4. Device Identifier Permanence

In terms of permanence, an IDevID is similar to a UEID in that they do not change over the life of the device. They cease to exist only when the device is destroyed.¶

An SUEID is similar to an LDevID. They change on device life-cycle events.¶

[IEEE.802.1AR] describes much of this permanence as resistant to attacks that seek to change the ID. IDevID permanence can be described this way because [IEEE.802.1AR] is oriented around the definition of an implementation with a particular level of defense against attack.¶

EAT is not defined around a particular implementation and must work on a range of devices that have a range of defenses against attack. EAT thus can't be defined permanence in terms of defense against attack. EAT's definition of permanence is in terms of operations and device lifecycle.¶

D.1. From draft-rats-eat-01

• Added UEID design rationale appendix¶

D.2. From draft-mandyam-rats-eat-00

This is a fairly large change in the orientation of the document, but no new claims have been added.¶

• Separate information and data model using CDDL.¶
• Say an EAT is a CWT or JWT¶
• Use a map to structure the boot_state and location claims¶

D.3. From draft-ietf-rats-eat-01

• Clarifications and corrections for OEMID claim¶
• Minor spelling and other fixes¶
• Add the nonce claim, clarify jti claim¶

D.4. From draft-ietf-rats-eat-02

• Roll all EUIs back into one UEID type¶
• UEIDs can be one of three lengths, 128, 192 and 256.¶
• Added appendix justifying UEID design and size.¶
• Submods part now includes nested eat tokens so they can be named and there can be more tha one of them¶
• Lots of fixes to the CDDL¶
• Added security considerations¶

D.5. From draft-ietf-rats-eat-03

• Split boot_state into secure-boot and debug-disable claims¶
• Debug disable is an enumerated type rather than Booleans¶

D.6. From draft-ietf-rats-eat-04

• Change IMEI-based UEIDs to be encoded as a 14-byte string¶
• CDDL cleaned up some more¶
• CDDL allows for JWTs and UCCSs¶
• CWT format submodules are byte string wrapped¶
• Allows for JWT nested in CWT and vice versa¶
• Allows UCCS (unsigned CWTs) and JWT unsecured tokens¶
• Clarify tag usage when nesting tokens¶
• Add section on key inclusion¶
• Add hardware version claims¶
• Collected CDDL is now filled in. Other CDDL corrections.¶
• Rename debug-disable to debug-status; clarify that it is not extensible¶
• Security level claim is not extensible¶
• Improve specification of location claim and added a location privacy section¶
• Add intended use claim¶

D.7. From draft-ietf-rats-eat-05

• CDDL format issues resolved¶
• Corrected reference to Location Privacy section¶

D.8. From draft-ietf-rats-eat-06

• Added boot-seed claim¶
• Rework CBOR interoperability section¶
• Added profiles claim and section¶

D.9. From draft-ietf-rats-eat-07

• Filled in IANA and other sections for possible preassignment of Claim Keys for well understood claims¶

D.10. From draft-ietf-rats-eat-08

• Change profile claim to be either a URL or an OID rather than a test string¶

D.11. From draft-ietf-rats-eat-09

• Add SUEIDs¶
• Add appendix comparing IDevID to EAT¶
• Added section on use for Evidence and Attestation Results¶
• Fill in the key ID and endorsements identificaiton section¶
• Remove origination claim as it is replaced by key IDs and endorsements¶
• Added manifests and software evidence claims¶
• Add string labels non-claim labels for use with JSON (e.g. labels for members of location claim)¶
• EAN-13 HW versions are no longer a separate claim. Now they are folded in as a CoSWID version scheme.¶

D.12. From draft-ietf-rats-eat-10

• Hardware version is made into an array of two rather than two claims¶
• Corrections and wording improvements for security levels claim¶
• Add swresults claim¶
• Add dloas claim - Digitial Letter of Approvals, a list of certifications¶
• CDDL for each claim no longer in a separate sub section¶
• Consistent use of terminology from RATS architecture document¶
• Consistent use of terminology from CWT and JWT documents¶
• Remove operating model and procedures; refer to CWT, JWT and RATS architecture instead¶
• Some reorganization of Section 1¶
• Moved a few references, including RATS Architecture, to informative.¶
• Add detached submodule digests and detached eat bundles (DEBs)¶
• New simpler and more universal scheme for identifying the encoding of a nested token¶
• Made clear that CBOR and JSON are only mixed when nesting a token in another token¶
• Clearly separate CDDL for JSON and CBOR-specific data items¶
• Define UJCS (unsigned JWTs)¶
• Add CDDL for a general Claims-Set used by UCCS, UJCS, CWT, JWT and EAT¶
• Top level CDDL for CWT correctly refers to COSE¶
• OEM ID is specifically for HW, not for SW¶
• HW OEM ID can now be a PEN¶
• HW OEM ID can now be a 128-bit random number¶
• Expand the examples section¶
• Add software and version claims as easy / JSON alternative to CoSWID¶

D.13. From draft-ietf-rats-eat-11

• Add HW model claim¶
• Change reference for CBOR OID draft to RFC 9090¶
• Correct the iat claim in some examples¶
• Make HW Version just one claim rather than 3 (device, board and chip)¶
• Remove CDDL comments from CDDL blocks¶
• More clearly define "entity" and use it more broadly, particularly instead of "device"¶
• Re do early allocation of CBOR labels since last one didn't complete correctly¶
• Lots of rewording and tightening up of section 1¶
• Lots of wording improvements in section 3, particularly better use of normative language¶
• Improve wording in submodules section, particularly how to distinguish types when decoding¶
• Remove security-level from early allocation¶
• Add boot odometer claim¶
• Add privacy considerations for replay protection¶