2023-09-25 AnonCreds v2.0 Working Group Meeting

Summary

• Hyperledger Labs Agora – an implementation of (the planned) AnonCreds 2.0 – and more!
• Open Discussion

Zoom Link: 

Recording of Call:  

Notices: 

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

Meeting Attendees

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

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

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 Rust 0.2.0-dev1 released! Update to AnonCreds CL Signatures implementation with fixes and performance improvements.

Agenda

• Hyperledger Labs Agora – an implementation of (the planned) AnonCreds 2.0 – and more!
  • "Unknown Order" library – wrapper of all the well known BigNumber libraries – pick a back end, go...
    • Constant time libraries for security.
    • Why "unknown order" – don't know the order unless you know the secret – MPC relies on a group of Big Nums unknown_order – blob of binary that you have to know about to interpret
    • Side note: class groups is coming for a similar purpose
  • Paillier RS
  • blsful ("Blissful") – BLS Signatures – everything in BLS Signatures, and what's needed in AnonCreds 2.0.
    • Signing, verifying, threshold signing, assembling
    • Algomar proofs Key shares
    • sign_crypt – sign and encrypt/decrypt and verify
    • Wrapper around Intel's blst ("Blast") library – hides
  • CredX – anoncreds 2.0
    • Not part of Agora – likely to go to AnonCreds directly.
    • Being worked to break out the components, so CredX is more glue, less cryptography.
• Open Discussion

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:

Schema Claim Type:

• Would it make sense defining encodings for date related schema claim types that are especially useful to use in ZKP predicates?
  • "iso860_date" – encodes to dateint e.g., 2023.06.26 is 20230626
  • "iso860_datetime" - encodes to Unix Time e.g., seconds since Jan 1, 1970
• Yes – these would be "numbers" by type, but with special encoding handling.

Action items