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)