Summary

Recording of Call:  20230501 AnonCreds V2.0 Working Group Call Recording.mp4

Notices: 

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Meeting Attendees

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

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

Related Repositories:

Goals of the Working Group:

The goal of AnonCreds v2.0 is to retain and extend the privacy-preserving features of AnonCreds v1.0, while improving capabilities, performance, extensibility, and security.

Meeting Preliminaries:

  • Welcome and Introductions
  • Announcements:
    • AnonCreds Workshop presented by Hyperledger is planned for May 31, 2023, 8:00 Pacific / 17:00 Central Europe. Details to be shared.
    • I'll be talking at the Linux Foundation Open Source Summit, Metaverse Conference about Hyperledger AnonCreds and ZKPs.
  • Updates to the Agenda?

Agenda

  • Proposed data models discussion given what Mike Lodder has presented and documented here: https://hackmd.io/ZlsnLoclSveePJOZljgMfA
    • Issuing AnonCreds v1.0:
      • Schema – simple list of attribute names, schema name, version
        • Attribute type is dynamically implied by the data in the credential – string or integer
      • Credential Definition – a signing key for each attribute, an extra field that is the link secret
      • Credential
        • Raw and encoded claims
        • Signature is added
    • Issuing v2.0
      • From document – items:
        • Claims – Schema, Validators, Data
        • Credential Schema, Credential Definition 
        • Credential
      • Proposal that types are defined in the AnonCreds specification 
      • Claims Schema Repository
        • Name, ID, type, validators
        • QUESTION: Do we want to add the complexity/overhead of adding this element vs. keeping all of the information encapsulated in the Credential Schema Object
          • Could have an optional "ClaimsSchemaId" as optional in the "Credential Schema Object":
            • When included, only the Claims Name/ID need be included in the Credential Schema Object
            • When not included, the full Claims information (type, validators) must be included in the Credential Schema Object.
      • Credential Schema Object:
        • Name, Description (should also have version?) 
        • Blindly Signed Claims Schema
          • Attribute name/ID from Claims Schema
        • Ordered List: Claims Schema
          • Attribute name/ID from Claims Schema, or
          • Attribute Name, ID, type, validators
      • Credential Definition Object
        • Keys necessary to sign credentials
          • Parameters per attribute – could be derived when using some signature schemes
        • ID of Schema Object
        • Revocation Registry – keys
      • Credential:
        • Claims
        • Signature
        • Revocation Registry Handle
        • Credential Definition ID
    • Signature Schemes
      • CL
      • BLS - doesn't support selective disclosure
      • BBS+ - IETF submitted version can be used
        • PQ unlikely – none known at this time.
      • PS - Mike, et. al (potentially including "S" in "PS") is taking this to IETF
        • Has a post-quantum version, but slower and bigger
          • Calculation for 5 claims – in the Credential Definition: Public Key 912 bytes, PQ version: 6KB, increasing linearly (6x bigger)
            • Proof: 300-400 bytes, PQ version: 24kb (50x bigger)
          • Could be public key could be fixed size 192b and then derive a per claim data parameter (tradeoff size vs. time)

Future Calls

  • Collect some use case specific examples and continue the discussions:
    • Applying the data structures to a real use case or two
      • Take an existing AnonCreds Schema (maybe this) and Credential Definition (maybe this) and define what it would be using Mike's proposed data models.
        • Where would the data models exist, such as on ledger, in the AnonCreds specification?
    • What concrete uses other than link-secret is there for blinded data in a credential?

To Dos:

Action items