Internet Engineering Task Force (IETF) L. Lundblade
Request for Comments: 9782 Security Theory LLC
Category: Standards Track H. Birkholz
ISSN: 2070-1721 Fraunhofer SIT
T. Fossati
Linaro
April 2025
Entity Attestation Token (EAT) Media Types
Abstract
Payloads
The payloads used in Remote ATtestation procedureS (RATS) may require
an associated media type for their conveyance, for example, when the
payloads are used in RESTful APIs.
This memo defines media types to be used for Entity Attestation
Tokens (EATs).
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9782.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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in the Revised BSD License.
Table of Contents
1. Introduction
1.1. Terminology
2. EAT Types
3. A Media Type Parameter for EAT Profiles
4. Examples
5. Security Considerations
6. IANA Considerations
6.1. +cwt Structured Syntax Suffix
6.1.1. Registry Contents
6.2. Media Types
6.3. application/eat+cwt Registration
6.4. application/eat+jwt Registration
6.5. application/eat-bun+cbor Registration
6.6. application/eat-bun+json Registration
6.7. application/eat-ucs+cbor Registration
6.8. application/eat-ucs+json Registration
6.9. CoAP Content-Format Registrations
7. References
7.1. Normative References
7.2. Informative References
Acknowledgments
Authors' Addresses
1. Introduction
Payloads used in Remote ATtestation procedureS (RATS) [RATS-ARCH] may
require an associated media type for their conveyance, for example,
when used in RESTful APIs (Figure 1).
.---------------. .----------. .----------.
| Relying Party | | Attester | | Verifier |
'-+-------------' '----+-----' '--------+-'
| | POST /verify |
| | EAT(Evidence) |
| +--------------------------->|
| | 200 OK |
| | EAT(Attestation Results) |
| |<---------------------------+
| POST /auth | |
| EAT(Attestation Results) | |
|<---------------------------+ |
| 201 Created | |
+--------------------------->| |
| | |
| | |
Figure 1: Conveying RATS Conceptual Messages in REST APIs Using EATs
This memo defines media types to be used for EAT payloads [EAT]
independently of the RATS Conceptual Message in which they manifest
themselves. The objective is to give protocol, API, and application
designers a number of readily available and reusable media types for
integrating EAT-based messages in their flows, e.g., when using HTTP
[BUILD-W-HTTP] or the Constrained Application Protocol (CoAP)
[REST-IoT].
1.1. Terminology
This document uses the terms and concepts defined in [RATS-ARCH].
2. EAT Types
Figure 2 illustrates the six EAT wire formats and how they relate to
each other. [EAT] defines four of them (CBOR Web Token (CWT), JSON
Web Token (JWT), (JWT) [JWT], and the detached EAT bundle in its JSON and
CBOR flavours), while [UCCS] defines the Unprotected CWT Claims Set
(UCCS) and Unprotected JWT Claims Sets (UJCS).
.-----.
.----+ UJCS |<-------------------------.
| '-----' |
| |
| .-----. |
+-----+ UCCS |<-----------------------. |
| '-----' | |
| | |
| .------. | |
+-----+ JWT |<------. | |
| '------' .--+---. | |
| | Crypto |<------. | |
| .------. '--+---' | | |
+-----+ CWT |<------' | | |
| '------' .---+-+-+----.
| | Claims-Set +--.
| .------. '---+---+----' |
+-----+ BUN-J |<------. | ^ | v
| '------' .--+---. | | | .------.
| | Bundle |<------' | | | Digest |
| .------. '--+---' | v '--+---'
+-----+ BUN-C |<------' ^ .---+----. |
| '------' | | submod |<---'
| | '--------'
v | ^
.--------------. | |
| Nested-Token +-----------------+------------'
'--------------'
.-------. .---------. .------.
Legend: | Process | | Wire Fmt | | CDDL |
'-------' '---------' '------'
Figure 2: EAT Types
3. A Media Type Parameter for EAT Profiles
EAT is an open and flexible format. To improve interoperability,
Section 6 of [EAT] defines the concept of EAT profiles. Profiles are
used to constrain the parameters that producers and consumers of a
specific EAT profile need to understand in order to interoperate,
e.g., the number and type of claims, which serialisation format, the
supported signature schemes, etc. EATs carry an in-band profile
identifier using the eat_profile "eat_profile" claim (see Section 4.3.2 of
[EAT]). The value of the eat_profile "eat_profile" claim is either an OID or a
URI.
The media types defined in this document include an optional
eat_profile
"eat_profile" parameter that can be used to mirror the eat_profile "eat_profile"
claim of the transported EAT. Exposing the EAT profile at the API
layer allows API routers to dispatch payloads directly to the
profile-specific processor without having to snoop into the request
bodies. This design also provides a finer-grained and scalable type
system that matches the inherent extensibility of EAT. The
expectation being that a certain EAT profile automatically obtains a
media type derived from the base (e.g., application/eat+cwt) by
populating the eat_profile "eat_profile" parameter with the corresponding OID or
URL.
When the parameterised version of the EAT media type is used in HTTP
(for example, with the "Content-Type" and "Accept" headers) and the
value is an absolute URI (Section 4.3 of [URI]), the parameter-value
(Appendix A of [HTTP]) uses the quoted-string encoding, for example:
application/eat+jwt; eat_profile="tag:evidence.example,2022"
Instead, when the EAT profile is an OID, the token encoding (i.e.,
without quotes) can be used. For example:
application/eat+cwt; eat_profile=2.999.1.
4. Examples
The example in Figure 3 illustrates the usage of EAT media types for
transporting attestation evidence as well as negotiating the
acceptable format of the attestation result.
NOTE: '\' line wrapping per RFC 8792
POST /challenge-response/v1/session/1234567890 HTTP/1.1
Host: verifier.example
Accept: application/eat+cwt; eat_profile="tag:ar4si.example,2021"
Content-Type: application/eat+cwt; \
eat_profile="tag:evidence.example,2022"
[ CBOR-encoded EAT w/ eat_profile="tag:evidence.example,2022" ]
Figure 3: Example REST Verification API (request)
The example in Figure 4 illustrates the usage of EAT media types for
transporting attestation results.
NOTE: '\' line wrapping per RFC 8792
HTTP/1.1 200 OK
Content-Type: application/eat+cwt; \
eat_profile="tag:ar4si.example,2021"
[ CBOR-encoded EAT w/ eat_profile="tag:ar4si.example,2021" ]
Figure 4: Example REST Verification API (response)
In both cases, a tag URI [TAG] identifying the profile is carried as
an explicit parameter.
5. Security Considerations
Media types only provide clues to the processing application. The
application must verify that the received data matches the expected
format, regardless of the advertised media type, and stop further
processing on failure. Failing to do so could expose the user to
security risks, such as privilege escalation and cross-protocol
attacks.
The security considerations of [EAT] and [UCCS] apply in full.
When using application/eat-ucs+json and application/eat-ucs+cbor in
particular, the reader should review Section 3 of [UCCS], which
contains a detailed discussion about the characteristics of a "Secure
Channel" for conveyance of such messages.
6. IANA Considerations
6.1. +cwt Structured Syntax Suffix
IANA has registered +cwt in the "Structured Syntax Suffixes" registry
[STRUCT-SYNTAX] in the manner described in [MEDIATYPES]. +cwt can be
used to indicate that the media type is encoded as a CWT.
6.1.1. Registry Contents
Name: CBOR Web Token (CWT)
+suffix: +cwt
References: [CWT]
Encoding Considerations: binary
Interoperability Considerations: N/A
Fragment Identifier Considerations: The syntax and semantics of
fragment identifiers specified for +cwt SHOULD be as specified for
application/cwt. (At the time of publication, there is no
fragment identification syntax defined for application/cwt.)
Security Considerations: See Section 8 of [CWT]
Contact: RATS WG mailing list (rats@ietf.org), or IETF Security Area
(saag@ietf.org)
Author/Change Controller: Remote ATtestation ProcedureS (RATS)
Working Group. The IETF has change control over this
registration.
6.2. Media Types
IANA has registered the following media types in the "Media Types"
registry [MEDIA-TYPES].
+==============+=====================+=======================+
| Name | Template | Reference |
+==============+=====================+=======================+
| EAT CWT | application/eat+cwt | RFC 9782, Section 6.3 |
+--------------+---------------------+-----------------------+
| EAT JWT | application/eat+jwt | RFC 9782, Section 6.4 |
+--------------+---------------------+-----------------------+
| Detached EAT | application/eat- | RFC 9782, Section 6.5 |
| Bundle CBOR | bun+cbor | |
+--------------+---------------------+-----------------------+
| Detached EAT | application/eat- | RFC 9782, Section 6.6 |
| Bundle JSON | bun+json | |
+--------------+---------------------+-----------------------+
| EAT UCCS | application/eat- | RFC 9782, Section 6.7 |
| | ucs+cbor | |
+--------------+---------------------+-----------------------+
| EAT UJCS | application/eat- | RFC 9782, Section 6.8 |
| | ucs+json | |
+--------------+---------------------+-----------------------+
Table 1: New Media Types
6.3. application/eat+cwt Registration
Type name: application
Subtype name: eat+cwt
Required parameters: n/a
Optional parameters: "eat_profile" (EAT profile in string format.
OIDs must use the dotted-decimal notation. The parameter value is
case insensitive.)
Encoding considerations: binary
Security considerations: Section 9 of [EAT]
Interoperability considerations: n/a
Published specification: RFC 9782
Applications that use this media type: Attesters, Verifiers,
Endorsers and Reference-Value providers, and Relying Parties that
need to transfer EAT payloads over HTTP(S), CoAP(S), and other
transports.
Fragment identifier considerations: n/a
Person & email address to contact for further information: RATS WG
mailing list (rats@ietf.org)
Intended usage: COMMON
Restrictions on usage: none
Author/Change controller: IETF
Provisional registration: no
6.4. application/eat+jwt Registration
Type name: application
Subtype name: eat+jwt
Required parameters: n/a
Optional parameters: "eat_profile" (EAT profile in string format.
OIDs must use the dotted-decimal notation. The parameter value is
case insensitive.)
Encoding considerations: 8bit
Security considerations: Section 9 of [EAT] and [BCP225]
Interoperability considerations: n/a
Published specification: RFC 9782
Applications that use this media type: Attesters, Verifiers,
Endorsers and Reference-Value providers, and Relying Parties that
need to transfer EAT payloads over HTTP(S), CoAP(S), and other
transports.
Fragment identifier considerations: n/a
Person & email address to contact for further information: RATS WG
mailing list (rats@ietf.org)
Intended usage: COMMON
Restrictions on usage: none
Author/Change controller: IETF
Provisional registration: no
6.5. application/eat-bun+cbor Registration
Type name: application
Subtype name: eat-bun+cbor
Required parameters: n/a
Optional parameters: "eat_profile" (EAT profile in string format.
OIDs must use the dotted-decimal notation. The parameter value is
case insensitive.)
Encoding considerations: binary
Security considerations: Section 9 of [EAT]
Interoperability considerations: n/a
Published specification: RFC 9782
Applications that use this media type: Attesters, Verifiers,
Endorsers and Reference-Value providers, and Relying Parties that
need to transfer EAT payloads over HTTP(S), CoAP(S), and other
transports.
Fragment identifier considerations: n/a
Person & email address to contact for further information: RATS WG
mailing list (rats@ietf.org)
Intended usage: COMMON
Restrictions on usage: none
Author/Change controller: IETF
Provisional registration: no
6.6. application/eat-bun+json Registration
Type name: application
Subtype name: eat-bun+json
Required parameters: n/a
Optional parameters: "eat_profile" (EAT profile in string format.
OIDs must use the dotted-decimal notation. The parameter value is
case insensitive.)
Encoding considerations: Same as [JSON]
Security considerations: Section 9 of [EAT]
Interoperability considerations: n/a
Published specification: RFC 9782
Applications that use this media type: Attesters, Verifiers,
Endorsers and Reference-Value providers, and Relying Parties that
need to transfer EAT payloads over HTTP(S), CoAP(S), and other
transports.
Fragment identifier considerations: n/a
Person & email address to contact for further information: RATS WG
mailing list (rats@ietf.org)
Intended usage: COMMON
Restrictions on usage: none
Author/Change controller: IETF
Provisional registration: no
6.7. application/eat-ucs+cbor Registration
Type name: application
Subtype name: eat-ucs+cbor
Required parameters: n/a
Optional parameters: "eat_profile" (EAT profile in string format.
OIDs must use the dotted-decimal notation. The parameter value is
case insensitive.)
Encoding considerations: binary
Security considerations: Sections 3 and 7 of [UCCS]
Interoperability considerations: n/a
Published specification: RFC 9782
Applications that use this media type: Attesters, Verifiers,
Endorsers and Reference-Value providers, and Relying Parties that
need to transfer EAT payloads over HTTP(S), CoAP(S), and other
transports.
Fragment identifier considerations: n/a
Person & email address to contact for further information: RATS WG
mailing list (rats@ietf.org)
Intended usage: COMMON
Restrictions on usage: none
Author/Change controller: IETF
Provisional registration: no
6.8. application/eat-ucs+json Registration
Type name: application
Subtype name: eat-ucs+json
Required parameters: n/a
Optional parameters: "eat_profile" (EAT profile in string format.
OIDs must use the dotted-decimal notation. The parameter value is
case insensitive.)
Encoding considerations: Same as [JSON]
Security considerations: Sections 3 and 7 of [UCCS]
Interoperability considerations: n/a
Published specification: RFC 9782
Applications that use this media type: Attesters, Verifiers,
Endorsers and Reference-Value providers, and Relying Parties that
need to transfer EAT payloads over HTTP(S), CoAP(S), and other
transports.
Fragment identifier considerations: n/a
Person & email address to contact for further information: RATS WG
mailing list (rats@ietf.org)
Intended usage: COMMON
Restrictions on usage: none
Author/Change controller: IETF
Provisional registration: no
6.9. CoAP Content-Format Registrations
IANA has registered the following Content-Format numbers in the "CoAP
Content-Formats" registry, within the "Constrained RESTful
Environments (CoRE) Parameters" registry group [CORE-PARAMS]:
+==========================+================+=====+===========+
| Content Type | Content Coding | ID | Reference |
+==========================+================+=====+===========+
| application/eat+cwt | - | 263 | RFC 9782 |
+--------------------------+----------------+-----+-----------+
| application/eat+jwt | - | 264 | RFC 9782 |
+--------------------------+----------------+-----+-----------+
| application/eat-bun+cbor | - | 265 | RFC 9782 |
+--------------------------+----------------+-----+-----------+
| application/eat-bun+json | - | 266 | RFC 9782 |
+--------------------------+----------------+-----+-----------+
| application/eat-ucs+cbor | - | 267 | RFC 9781 |
+--------------------------+----------------+-----+-----------+
| application/eat-ucs+json | - | 268 | RFC 9782 |
+--------------------------+----------------+-----+-----------+
Table 2: New Content-Formats
7. References
7.1. Normative References
[BCP225] Best Current Practice 225,
<https://www.rfc-editor.org/info/bcp225>.
At the time of writing, this BCP comprises the following:
Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
Current Practices", BCP 225, RFC 8725,
DOI 10.17487/RFC8725, February 2020,
<https://www.rfc-editor.org/info/rfc8725>.
[CORE-PARAMS]
IANA, "CoAP Content-Formats",
<https://www.iana.org/assignments/core-parameters>.
[CWT] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/info/rfc8392>.
[EAT] Lundblade, L., Mandyam, G., O'Donoghue, J., and C.
Wallace, "The Entity Attestation Token (EAT)", RFC 9711,
DOI 10.17487/RFC9711, April 2025,
<https://www.rfc-editor.org/info/rfc9711>.
[HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.
[JSON] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
[JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[MEDIA-TYPES]
IANA, "Media Types",
<https://www.iana.org/assignments/media-types>.
[MEDIATYPES]
Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>.
[STRUCT-SYNTAX]
IANA, "Structured Syntax Suffixes",
<https://www.iana.org/assignments/media-type-structured-
suffix>.
[UCCS] Birkholz, H., O'Donoghue, J., Cam-Winget, N., and C.
Bormann, "A Concise Binary Object Representation (CBOR)
Tag for Unprotected CBOR Web Token Claims Sets (UCCS)",
RFC 9781, DOI 10.17487/RFC9781, April 2025,
<https://www.rfc-editor.org/info/rfc9781>.
[URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
7.2. Informative References
[BUILD-W-HTTP]
Best Current Practice 56,
<https://www.rfc-editor.org/info/bcp56>.
At the time of writing, this BCP comprises the following:
Nottingham, M., "Building Protocols with HTTP", BCP 56,
RFC 9205, DOI 10.17487/RFC9205, June 2022,
<https://www.rfc-editor.org/info/rfc9205>.
[RATS-ARCH]
Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
W. Pan, "Remote ATtestation procedureS (RATS)
Architecture", RFC 9334, DOI 10.17487/RFC9334, January
2023, <https://www.rfc-editor.org/info/rfc9334>.
[REST-IoT] Keränen, A., Kovatsch, M., and K. Hartke, "Guidance on
RESTful Design for Internet of Things Systems", Work in
Progress, Internet-Draft, draft-irtf-t2trg-rest-iot-15, 21
October 2024, <https://datatracker.ietf.org/doc/html/
draft-irtf-t2trg-rest-iot-15>. draft-irtf-t2trg-rest-iot-16, 23
April 2025, <https://datatracker.ietf.org/doc/html/draft-
irtf-t2trg-rest-iot-16>.
[TAG] Kindberg, T. and S. Hawke, "The 'tag' URI Scheme",
RFC 4151, DOI 10.17487/RFC4151, October 2005,
<https://www.rfc-editor.org/info/rfc4151>.
Acknowledgments
Thank you Carl Wallace, Carsten Bormann, Dave Thaler, Deb Cooley,
Éric Vyncke, Francesca Palombini, Jouni Korhonen, Kathleen Moriarty,
Michael Richardson, Murray Kucherawy, Orie Steele, Paul Howard, Roman
Danyliw, and Tim Hollebeek for your comments and suggestions.
Authors' Addresses
Laurence Lundblade
Security Theory LLC
Email: lgl@securitytheory.com
Henk Birkholz
Fraunhofer Institute for Secure Information Technology
Rheinstrasse 75
64295 Darmstadt
Germany
Email: henk.birkholz@ietf.contact
Thomas Fossati
Linaro
Email: thomas.fossati@linaro.org