Functieomschrijving
Master Thesis project proposal
“Designing and implementing an ECDSA-based Zero-Knowledge Credential Architecture for Yivi as EUDI Wallet”
Context and motivation
Background
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 OpenID4VCI 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.
Strategic challenge
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 BLS12-381).
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 OpenID4VCI / OpenID4VP and standard verifiers,
And 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,
And potentially integrate with standard protocols such as OpenID4VCI 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.
Research objectives
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 OpenID4VCI and OpenID4VP,
And 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 OpenID4VCI and OpenID4VP
How can the proposed ECDSA-ZKP architecture:
Represent credentials and proofs in W3C VC formats (e.g. JWT/SD-JWT-VC or Data Integrity profiles)
Be transported using OpenID4VCI for issuance and OpenID4VP for presentations
Interoperate with verifiers that: Support advanced ZKP-proof types, and
Only support “classic” JWT/SD-JWT verification (graceful degradation / dual-path designs)
RQ5: Evaluation and recommendations
To what extent does the proposed architecture:
Meet the ETSI TR 119 476 criteria for privacy-preserving credentials,
Achieve practical performance for mobile wallets and verifiers,
Provide a realistic migration path for Yivi towards EUDI-compliant, ECDSA-based ZKP credentials?
What recommendations can be made to Yivi for:
Short-term experimentation (e.g. Longfellow-style wrapping of existing credentials), and
Long-term architecture choices (e.g. adoption of BBS# or hybrid designs)?
Student profile
We are looking for a motivated university-level student in Computer Science, Cyber Security or a closely related discipline. You have a strong affinity with cryptography, digital identity, and privacy-preserving technologies, and you are eager to apply academic knowledge to a real-world, high-impact use case. You work independently, think analytically, and are comfortable exploring complex technical concepts.
Thesis benefits
Professional supervision from specialists in cryptography, identity management, and EUDI Wallet technologies
Regular feedback and technical sparring sessions throughout the thesis process
Access to technical documentation, development environments, and research materials relevant to the assignment
A monthly thesis compensation of €500 (based on a 40-hour commitment; exceptions possible)
Flexible working arrangements, including hybrid work options
Opportunities to publish or present your research within the organization
Real-world impact: your work may directly contribute to the integration of Yivi as an EUDI Wallet
References
Academic
Anonymous credentials from ECDSA https://eprint.iacr.org/2024/2010
Privacy-Preserving Credentials: Camenisch et al https://eprint.iacr.org/2014/468.pdf
ETSI TR 119 476 - Electronic Signatures and Trust Infrastructures (ESI); Analysis of selective disclosure and zero-knowledge proofs applied to Electronic Attestation of Attributes https://www.etsi.org/deliver/etsi_tr/119400_119499/119476/01.02.01_60/tr_ 119476v010201p.pdf
BBS# and eIDAS 2.0 https://csrc.nist.gov/csrc/media/presentations/2024/wpec2024-3b3/images-media/wpec2024-3b3-slides-antoine-jacques--BBS-sharp-eIDAS2.pdf
Other
What is Yivi https://docs.yivi.app/what-is-yivi
IRMAGO https://github.com/privacybydesign/irmago
EUDI Wallet ARF: EU Commission - Regulatory framework https://eudi.dev/2.5.0/architecture-and-reference-framework-main/
Contact
Primary contact person
Dibran Mulder, CTO Caesar Groep & Yivi
+31 (0)6 39 30 61 18
Address:
Janssoniuslaan 80
3528 AJ Utrecht
Websites:
https://yivi.app
https://caesar.nl