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

Notices: 

This specification creating group operates under the Linux Foundation Community Specification License v1.0.

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

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

Related Repositories:

• Mike Lodder's proposed Data Models: https://hackmd.io/ZlsnLoclSveePJOZljgMfA
• AnonCreds v2.0 Specification Repository: https://github.com/hyperledger/anoncreds-spec-v2/
• AnonCreds v1.0 Specification: https://hyperledger.github.io/anoncreds-spec/
• AnonCreds Methods Registry: https://hyperledger.github.io/anoncreds-methods-registry
• AnonCreds Rust Open Source Code: https://github.com/hyperledger/anoncreds-rs

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• 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, type, validators
        • link secret
        Claims
        • /ID from Claims Schema
      • Ordered List: Claims Schema
        • Attribute name/ID from Claims Schema, or
        • Attribute Name, ID
        • Attribute name, 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?

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