Sietse Ringers, PhD

As an independent solution architect and software engineer, I specialize in digital identity: software implementing privacy-preserving cryptography and authentication technologies. During and after obtaining my PhD in 2016 I have specialized in cryptographic protocols and algorithms focusing on authentication, enabling me to design and implement secure software solutions with a strong focus on privacy-perserving technologies.

Skills

• Solution architect: designing software architecture
• Software engineer: developing software in a team or solo
• Cryptography: developing secure and privacy-friendly cryptographic algorithms and protocols

Technologies

A non-exhaustive list of technologies in which I am proficient and have experience with:

• Authentication: SD-JWT VC, mDL/mdoc, OpenID4VCI, OpenID4VP, OpenID Connect, OAuth, Yivi, X.509
• Cryptography: Idemix, BBS+, zero-knowledge proofs, TLS, signature schemes such as ECDSA, (a)symmetric encryption, AES, HMACs
• Software engineering: Rust, Go, JavaScript; git; open source (FOSS); agile (scrum/kanban)
• Writing technical documentation: software architecture design, developer documentation, technical and scientific articles

EDI NL Wallet

The EDI NL Wallet, as the Dutch implementation in development of the EU regulation on European Digital Identity, will enable dutch citizens to manage their digital identity in the NL wallet app, privacy-friendly and securely. The wallet app decentrally manages the user’s attestations of attributes, which have been issued by trusted issuer (QTSPs) to it and can be selectively disclosed from the wallet to relying parties (RPs) at level eIDAS Level of Assuarance High. I contribute to this project as an architect and software engineer. Source code, more information (Dutch).

Yivi

Yivi is a privacy-friendly, secure and easy-to-use authentication mechanism, using the Idemix attribute-based credential scheme as underlying credential scheme. In past work, as the architect and lead developer of Yivi I have designed and developed the majority of the core software: the server that can verify and issue attributes, the Yivi iOS/Android app core, and the protocols they use (source, documentation).

Cryptographical articles

• Using the RSA or RSA-B accumulator in anonymous credential schemes such as Idemix or BBS+
• A provably secure keyshare protocol, with David Venhoek
• Hashing into quadratic residues modulo a safe prime composite
• An efficient self-blindable attribute-based credential scheme, with Eric Verheul and Jaap-Henk Hoepman. Published in Financial Cryptography 2017 (FC’17). Slides.
• My PhD thesis: Quantization using Jet Space Geometry and Identity Management using Credential Schemes, which I defended on 7 October 2016 at the University of Groningen. If you would like a hardcopy, feel free to contact me.

Hire me

Are you interested in my services? Hire me! Feel free to contact me at sietse at primefactor.nl.

Contact

• mail at sietseringers.net (personal)
• sietse at primefactor.nl (business)