2023-02-06 AnonCreds Specification Working Group Meeting

Owned by Stephen Curran
Last updated: Feb 06, 2023
5 min read

Summary

  • Back to prover_did – not optional/not issuer generated?
  • WQL in Presentation Request?
  • PRs
  • Progress on the anoncreds_rs implementation
  • Open Discussion

Recording of Call: dummyfile.txt

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Meeting Attendees

Stephen Curran (BC Gov / Cloud Compass Computing Inc.) <swcurran@cloudcompass.ca>

Steve McCown (Anonyome Labs) <smccown@anonyome.com>

Ariel Gentile (2060.io) <gentilester@gmail.com>


Related Repositories:

Meeting Preliminaries:

  • Welcome and Introductions
  • Announcements:
  • Updates the Agenda

Agenda

Open Issue

  • Issues to Discuss
    • Issue #137 added regarding further investigation into what happens to the issuance data flow nonce(s) by Belsy – definition completed, to be added to the spec. Stephen Curran 
    • Issue #107 what happens to prover_did?  Decisions made:
      • Rename the item to entropy  
      • Update the spec and implementation (again) to make the item required from the holder
      • Describe how the item is combined with the rev_idx (if available) and hashed to produce the credential_context and put in the VC as m2 
      • m2 can be checked by the holder to ensure it is based the provided entropy value.
    • Issue #140 should WQL be allowed in a Presentation Request?
      • WQL is supported currently in the Indy SDK, but not in the Aries Frameworks
      • Should it be in the specification?
      • If so, in what form. From Sam Curren — don't call it WQL if we do include it – just describe it.
      • Not used and it is not clear there is a good reason to support it.
      • Complicates the specification and the implementation.
      • Decision:
        • Not supported in the specification – let's keep it out in this version
  • PRs for review and merging
    • Merged one of the two PRs in progress.
  • Checkin: anoncreds-rs implementation progress, requests
  • Discussion: Mike Lodder has proposed that a group start on "Next Gen" AnonCreds based on his this recorded presentation at out 2022-11-28 meeting
    • Stephen Curran to find times that work for Mike and propose times for the group.
  • Discussion – having an intermediary collect presentations from holders and then share them with the final verifier.
    • Use Case:
      • A bus is visiting a secure site for which all visitors must present ID.
      • Site sends the bus operator a nonce.
      • The bus operator uses the nonce in a presentation request flow with each passenger.
      • Bus operator verifies all of the presentations.
      • The Bus operator forwards all of the presentations to the site for verification.
    • Questions:
      • Is there value in the use of the nonce in this way?
      • Does this alter the cryptography in any way?
      • Terms of use of the data received by the bus operator?
    • Discussion to be carried forward to next week.

Future Calls

To Dos:

  • Revocation Interval
    • Approach to determine if the holder used an acceptable RevRegistry – see this Issue comment
    • Who calls the AnonCreds method to get the Revocation Registry from the ledger for verification
      • Verifier or AnonCreds?
    • To set "validation" to true/false based on the RevRegEntry timestamp in relation to the revocation interval?  Presentation 
    • Key points:
      • 1. an RevRegEntry is “current” from the time it is written, to the time of the next RevRegEntry
      • 2. “within the interval” is based on when a RevRegEntry is “current” (see 1.), not its timestamp.
      • 3. AnonCreds or the Verifier (calling AnonCreds) should calculate “within interval” (using 2.) and mark verification true if the RevRegEntry used by the Prover is within the interval, else false.
        • Dangers:
          • False-Negatives: If a strict "timestamp used is between from, to" and not based on when a RevReg is "current" (per 2.), we will get "not verified" incorrectly.
          • False-Positives: If we don't do any checking of the timestamp and the interval, the holder could incorrectly use an old RevRegEntry.
      • 4. General point: AnonCreds should return both a summary (true/false) and if false, additional data about why it was false.
    • Decision – add an optional `at_from_ts` set of entries, one per NRP, that AnonCreds can use for determining if the holder_ts is within the Presentation Request interval.
  • Backwards Compatibility
    • PRs in (#82, #105) that seem to change public data structures – ones that are handled outside of AnonCreds and/or by two or more participants (issuer, holder, verifier)
    • We want to retain compatibility with existing data – credentials that have been issued and the published AnonCreds objects on which they rely.
    • That extends to business logic – e.g. the handling of the objects not just by AnonCreds, AnonCreds Methods and Aries Frameworks, but also by business applications built on Aries.
    • Suggestion:
      • Include in the specification a statement about backward compatibility
        • Perhaps this is what Ankur had planned to do?
      • Formalize what data structures will be expected by AnonCreds
        • This is being done throughout the specification and verified against the current implementation.
      • As needed support sending and receiving data in "old" and "new" formats, but (for now) always sending "old" formats.
        • TBD if there are any such cases.

Action items