Session Date/Time: 21 Jul 2025 15:00

cose

Summary

The COSE working group meeting covered several active drafts, including Merkel tree proofs, the T-SATS-T header parameter, hash envelope, BLSki representation, Sphinx Plus, and Falcon. Discussions focused on the status of these drafts and potential future directions. A significant portion of the meeting was dedicated to a presentation on HPKE, including addressing feedback from the working group last call, and a discussion ensued around context information and the inclusion of COSE Mac. Additional presentations were on C-Bore encoded X509, ASCON, and split signing algorithms.

Key Discussion Points

Merkel Tree Proofs: In IESG evaluation, telechat scheduled.
T-SATS-T Header Parameter: Publication requested recently after rechartering, but it may need a new IETF last call.
Hash Envelope: Shepard write up is done, a new version from the authors is needed.
BLSki Representation: Updated to reference the current BBS signatures draft.
Sphinx Plus and Falcon: Actively seeking new editors. Polls were conducted to gauge interest in continuing work on these drafts.
HPKE: Extensive discussion regarding the context information structure. Debate ensued regarding the need for COSE Mac and associated use cases.
C-Bore Encoded X509: Working group last call ended. Discussions about request template, and comments about certificate chains, certificate hash and in a certificate type.
ASCON for COSE: A new proposal to add ASCON as an AAD algorithm to COSE was presented. Advantages in energy efficiency and throughput were highlighted.
Split Signing Algorithms: Discussed motivating use cases, potential problems with RSA and the addition of a cosi sign args structure to enable passing additional context.

Decisions and Action Items

HPKE:
- Move the recipient structure into the HPKE seal info parameter and prefix the context with an HPKE label. Sophie Schmidt volunteered to write a paragraph to the list explaining her suggestion.
- Remove COSE Mac from the HPKE draft due to lack of support.
- Authors will update the code, address editorial issues, and submit a new draft.
Sphinx Plus: Continue work, Hannes will remain an editor.
Falcon: Discontinue.
C-Bore Encoded X509: Authors will continue development, taking into consideration the recent feedback.
ASCON for COSE: Continue working on the draft. A call for reviewers was made.

Next Steps

Authors of respective drafts to address feedback received and produce updated versions.
Working group members to review the ASCON and Split Signing draft.
Discussion to continue on the mailing lists.