Master Thesis Project | ECDSA Zero- Credentials in Yivi’s EUDI Wallet

Master Thesis project proposal

“Designing and implementing an ECDSA-based Zero-Knowledge Credential Architecture for Yivi as EUDI Wallet”

Background

Yivi is a privacy-preserving digital identity platform that has produced production deployments using IRMA/Idemix protocols based on zero-knowledge proof (ZKP) schemes. With the EU Digital Identity (EUDI) Wallet regulation (eIDAS 2.0), Yivi aims to evolve into a compliant EUDI wallet while preserving its privacy guarantees and crypto-agile architecture.

The EUDI ecosystem standardises on:

• Verifiable Credentials (e.g. W3C VC, SD-JWT-VC, ISO 18013-5 mDL/MDOC)
• Presentation and issuance protocols such as OpenID4
  
  VCI and OpenID4VP
• Selective disclosure and zero-knowledge techniques, including BBS+, CL signatures and other privacy-enhancing cryptographic mechanisms

Yivi aims to leverage these developments while preserving its core privacy values: minimum disclosure, unlinkability, and user-controlled identity.

Strategic challenge

Today, many credentials are signed using ECDSA keys (e.g. JWT-based credentials, SD-JWT-VC, MDOC). Privacy-preserving credential systems often rely on different cryptographic primitives (e.g. CL, BBS+ on BLS
12-381).

Yivi faces a strategic challenge:

• How to evolve towards an EUDI-compliant wallet that reuses existing and widely deployed ECDSA key material
• Supports zero-knowledge proofs and selective disclosure
• Remains interoperable with OpenID4
  
  VCI / OpenID4VP and standard verifiers
• Preserves Yivi’s strong privacy guarantees and crypto-agility

The ECDSA-based ZKP opportunity

Recent work such as Google’s Longfellow project (“Anonymous credentials from ECDSA”) and new proposals around BBS# indicate that it is possible to:

• Build anonymous credential schemes on top of existing ECDSA-signed credentials
• Provide selective disclosure and unlinkable presentations
• Minimise changes to issuer infrastructure
• Potentially integrate with standard protocols such as OpenID4
  
  VCI and OpenID4VP

This opens the possibility for Yivi to design a next-generation ZKP layer that:

• Uses ECDSA keys as the fundamental trust anchor
• Compares and possibly combines Longfellow-style constructions with BBS+/BBS#-based approaches
• Is grounded in the requirements and recommendations of ETSI TR 119 476

Primary objective

Design and prototype an ECDSA-based zero-knowledge credential architecture for Yivi that:

• Provides selective disclosure and unlinkable presentations based on ECDSA keys
• Is aligned with the cryptographic and privacy requirements from ETSI TR 119 476
• Supports interoperability with OpenID4
  
  VCI and OpenID4VP
• Can be integrated into Yivi’s roadmap towards an EUDI-compliant wallet

Specific research questions

RQ1:
Requirements analysis based on ETSI TR 119 476. How can the privacy, security and interoperability requirements from ETSI TR 119 476 for selective disclosure and ZKP-based credentials be translated into concrete requirements for a Yivi ECDSA-ZKP architecture, in particular regarding:

• Unlinkability across presentations
• Minimal disclosure and predicate proofs
• Revocation and status verification
• Crypto-agility and (future) post-quantum considerations

RQ2: ECDSA-based ZKP design options (Longfellow vs BBS#/BBS+) What are the design trade-offs between:

• Longfellow / “Anonymous credentials from ECDSA” using existing ECDSA-signed credentials (JWT / SD-JWT-VC / MDOC) as the base
• Generating zero-knowledge proofs over attributes derived from these credentials
• BBS+/BBS#-based credentials anchored in ECDSA trust. Mapping Yivi (and EUDI) credential structures to BBS+/BBS# signatures
• Exploring how ECDSA-based PKI and BBS#/BBS+-based ZKP can be combined or bridged

RQ3:
Yivi architecture integration. How can an ECDSA-based ZKP scheme (Longfellow, BBS#, or a hybrid) be integrated into Yivi’s architecture while:

• Maintaining backward compatibility with existing IRMA/Idemix credentials where needed
• Supporting multiple credential formats (e.g. SD-JWT-VC, MDOC, IRMA) within Yivi
• Preserving Yivi’s privacy-first design, including unlinkability and minimal disclosure
• Allowing for crypto-agile evolution as standards mature

RQ4:
Interoperability with OpenID4

VCI and OpenID4VP. How can the…