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2023-03-13 AnonCreds Specification Working Group Meeting

2023-03-13 AnonCreds Specification Working Group Meeting

Mar 13, 2023

Summary

  • TIME CHANGE IN EUROPE – Call is one hour earlier than normal – 7:00 Pacific / 15:00 Central Europe

  • Update on the AnonCreds V2.0 Working Group

  • Hyperledger AnonCreds Workshop?

  • Question: The new Revocation Interface for Indy Ledgers – process? Working?

  • PRs

  • Issues to discuss

  • Checkin: anoncreds-rs implementation progress, requests

  • Open Discussion

Recording of Call:

 

Notices: 

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please visit the Hyperledger Code of Conduct.

Hyperledger is committed to creating a safe and welcoming

community for all. For more information

please visit the Hyperledger Code of Conduct.

Meeting Attendees

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

@Alex Andrei (RootsID)<alex.andrei@rootsid.com>

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

Related Repositories:

Meeting Preliminaries:

  • Welcome and Introductions

  • Announcements:

  • Any updates to the Agenda?

Agenda

Open Issue

  • Update on the AnonCreds V2.0 Working Group

    • Last week's meeting: Issuance Data Model proposals from Mike Lodder

    • Next week: Revisiting the Issuance Data Models OR Mike's Presentation Data Models

  • Hyperledger AnonCreds Workshop – interest? ideas for content?

    • Rodolofo volunteered to help

  • The new revocation process for Indy – is it working?  Implemented?

    • Change from

      • deltas and tails file to update the witness

    • to:

      • Deltas to full state

      • full state + tails file to create witness

  • PRs for review and merging

    • AnonCreds Rust 102 – handling combinations of Revoked/Non-Revoked presentations

      • Timestamp

      • Handling of both revocable and non-revocable credentials in a single presentation in all cases (bug in older implementation).

    • ANDs and ORs in the spec. are wrong – need to update the specification.

  • Issues to Discuss – notably, issues that are ready to be closed.

  • Checkin: anoncreds-rs implementation progress, requests

    • Fixes in the React Native side – registration, memory leaks, but largely figured out.

    • Tweaks and adjustments in AFJ, plus the revocation API.

  • Open Discussion: Possible topics:

    • Ideas on how to link from the specification to the math of the cryptographic operations?

    • Discussion from several weeks ago – 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.

    • Proposal: Should we move attribute encoding into the specification and out of the hands of the issuer?

      • Approach:

        • Deprecate the inclusion of encoded values from the "sign credential" process

        • If passed, recalculate and error if they don't match the canonicalization algorithm

          • If integer or string integer - leave as is

          • Else stringify and hash

        • In presentation – recalculate on use, as needed.

Future Calls

To Dos:

  • 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 #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

  • 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