WG Action: Rechartered CBOR Object Signing and Encryption (cose)

[The IESG <[e-mail]>]

The CBOR Object Signing and Encryption (cose) WG in the Security Area of the
IETF has been rechartered. For additional information, please contact the
Area Directors or the WG Chairs.

CBOR Object Signing and Encryption (cose)
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Current status: Active WG

Chairs:
  Ivaylo Petrov <[e-mail]>
  Michael Jones <[e-mail]>

Assigned Area Director:
  Paul Wouters <[e-mail]>

Security Area Directors:
  Paul Wouters <[e-mail]>
  Deb Cooley <[e-mail]>

Mailing list:
  Address: [e-mail]
  To subscribe: https://www.ietf.org/mailman/listinfo/cose
  Archive: https://mailarchive.ietf.org/arch/browse/cose/

Group page: https://datatracker.ietf.org/group/cose/

Charter: https://datatracker.ietf.org/doc/charter-ietf-cose/

CBOR Object Signing and Encryption (COSE, RFC 8152) describes how to
create and process signatures, message authentication codes, and
encryption using Concise Binary Object Representation (CBOR, RFC 7049)
for serialization. COSE additionally describes a representation for
cryptographic keys.

COSE has been picked up and is being used both by a number of groups
within the IETF (i.e., ACE, CORE, ANIMA, 6TiSCH and SUIT) and
outside the IETF (i.e., W3C and FIDO). There are a number of
implementations, both open source and private, now in existence.
The specification has advanced to STD status.

The COSE working group will deal with two types of documents going forward:

1.  Documents that describe the use of cryptographic algorithms in COSE.
2.  Documents which describe additional attributes for COSE.

The WG will evaluate, and potentially adopt, documents dealing with algorithms
that would fit the criteria of being IETF consensus algorithms.
Potential candidates would include those algorithms that have been evaluated
by the CFRG and algorithms which have gone through a public review and
evaluation process such as was done for the NIST SHA-3 algorithms. Potential
candidates would not include national-standards-based algorithms that have
not gone through a similar public review process.

The WG will produce documents for the below proposed and other possible new
attributes that are of interest to or requested by other WGs that are
consumers of COSE, with a general goal to complete the listed work items
before adopting new work

Key management and binding of keys to identities are out of scope for
the working group. The COSE WG will not innovate in terms of
cryptography. The specification of algorithms in COSE is limited to
those in RFCs, active CFRG or IETF WG documents, or algorithms which
have been positively reviewed by the CFRG.

The working group will coordinate its progress with the ACE, SUIT and
CORE working groups to ensure that it is fulfilling the needs of
these constituencies to the extent relevant to their work. Other
groups may be added to this list as the set of use cases is expanded,
in consultation with the responsible Area Director.

The WG currently has five work items:

1. One or more documents describing the proper use of algorithms.
These algorithms must meet the requirements outlined above.

2. A CBOR encoding of the certificate profile defined in RFC 5280.
It is expected that the encoding works with RFC 7925 and takes into
consideration any updates in draft-ietf-uta-tls13-iot-profile-00.  The
encoding may also include other important IoT certificate profiles like IEEE
802.1AR. This work is happening in draft-ietf-cose-cbor-encoded-cert.
The main objective is to define a method of encoding current X.509
certificates that meet a specific profile into a smaller format. This encoding
is invertible, so they can be expanded and normal X.509 certificate processing
can be used.  The data structures used for such encoding of X.509
certificates are expected to produce a compact encoding for certificate
information, and are not necessarily tied specifically to X.509 certificates.
 Accordingly, a secondary objective is to reuse these data structures to
produce a natively signed CBOR certificate encoding; such a structure is
relevant in situations where DER parsing and the machinery to convert between
CBOR and DER encodings are unnecessary overhead, such as embedded
implementations.  The possibility of a joint certificate artifact, conveyed
in CBOR encoding but including signatures over both the CBOR and DER
encodings, may be explored.  CBOR encoding of other X.509 certificate related
data structures may also be specified to support relevant functions such as
revocation: Certificate Revocation List (RFC 5280) or OSCP Request/Response
(RFC 6960); or certificate enrollment: Certificate Signing Request (RFC
2986). The working group will collaborate and coordinate with other IETF WGs
such as TLS, UTA, LAKE to understand and validate the requirements and
solution.

The WG has adopted and mostly completed work in the following three areas:

3. Representation formats and IANA assignments for COSE header parameters
that enable straightforward incorporation of RFC 3161-based timestamping
into COSE objects, enabling the use of established RFC 3161 timestamping
infrastructure to prove the creation time of a message
(draft-ietf-cose-tsa-tst-header-parameter-05, reached IESG evaluation before
 the gap in the charter was noticed)

4. Representation formats, IANA assignments for COSE header parameters, and
IANA registries that enable incorporating “COSE Receipts” into COSE objects,
enabling concise transparency via signed proofs that include metadata about
certain states of a verifiable data structure (VDS) that are true at the time
the COSE Receipt was issued. (the draft with the now somewhat dated file name
draft-ietf-cose-merkle-tree-proofs-13, was in IETF last call until 2025-05-13
and is waiting on a recharter before it is placed on the IESG ballot)

5. COSE header parameters for COSE objects that carry a payload that is an
output of a hash function on an original payload, enabling faster validation
s access to the original payload is not required for signature validation, and
proving hints of the original payload’s media type and potential availability
per reference (draft-ietf-cose-hash-envelope-05, approaching WGLC)

Milestones:

  Jun 2025 - COSE header parameters for RFC 3161-based timestamping into COSE
  objects to IESG

  Jun 2025 - COSE header parameters for incorporating “COSE Receipts” into
  COSE objects to IESG

  Jul 2025 - COSE header parameters for COSE objects that carry a payload
  that is an output of a hash function on an original payload to IESG

  Nov 2025 - A CBOR encoding of the certificate profile to the IESG

  Jan 2026 - One or more documents describing the proper use of algorithms.