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”

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

The EUDI ecosystem increasingly 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, analysed in detail in ETSI TR 119 476, including BBS+​, CL signatures and other privacy‑enhancing cryptographic mechanisms.

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

Today, many credentials in practice are signed using ECDSA keys (for example JWT‑based credentials, SD‑JWT‑VC, mDL/MDOC). At the same time, 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

• And preserves Yivi’s strong privacy guarantees and crypto‑agility.

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

• And 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

• And is grounded in the requirements and recommendations of ETSI TR 119 476.

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

• And can be integrated into Yivi’s roadmap towards an EUDI‑compliant wallet.

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…