Marvin Beckmann

Room 229

Richard Petersens Plads 322

2800 Kongens Lyngby, Denmark

My research interests include, but are not limited to:

(Privacy-preserving) authentication, e.g., ring signatures, blind signatures and deniable authenticated key exchange.
The intersection of quantum information and post-quantum cryptography with impact to practical parameters.

I am currently a PhD student supervised by Christian Majenz and co-supervised by Carsten Baum at DTU. I completed my Computer Science Bachelor’s and Master’s degree at Paderborn University under the supervision of Johannes Blömer working on lattice-based authentication.

News

May 15, 2026	Our paper Quantum Oracle Distribution Switching and its Applications to Fully Anonymous Ring Signatures has been accepted for a talk at QCrypt 2026 in Ottawa. We take a closer look at how quantum oracle indistinguishability behaves when the closeness of two distributions is measured using the Rényi divergence instead of statistical distance, and apply our results to give QROM proofs for various ring signature constructions — crucial for post-quantum Signal-conform key exchange.
Mar 20, 2026	Our paper Concretely Efficient Blind Signatures Based on VOLE-in-the-Head Proofs and the MAYO Trapdoor has been accepted for a talk at PrivCrypt2026 (affiliated event at Eurocrypt 2026), where I will talk about our work.
Dec 20, 2025	Our paper Concretely Efficient Blind Signatures Based on VOLE-in-the-Head Proofs and the MAYO Trapdoor has been accepted at USENIX Security 2026. We propose PoMFRIT, a post-quantum blind signature scheme that follows the standard Fischlin-style blind signature paradigm where the zero-knowledge proof for MAYO (and SHAKE256) is constructed using VOLEitH.

Selected Publications

Quantum Oracle Distribution Switching and its Applications to Fully Anonymous Ring Signatures

Marvin Beckmann and Christian Majenz

arXiv preprint arXiv:2602.16268, 2026

Abs arXiv eprint
Concretely Efficient Blind Signatures Based on VOLE-in-the-Head Proofs and the MAYO Trapdoor

Carsten Baum, Marvin Beckmann, Ward Beullens, Shibam Mukherjee, and Christian Rechberger

Cryptology ePrint Archive, 2026

Abs eprint

Blind signatures (Chaum, CRYPTO 82) are important building blocks in many privacy-preserving applications, such as anonymous credentials or e-cash schemes. Recent years saw a strong interest in building Blind signatures from post-quantum assumptions, primarily from lattices. While performance has improved, no construction has reached practical efficiency in terms of computation and communication. The state of the art requires at least 20 KB size of communication for each showing of a lattice-based Blind signature to a verifier, and more than 100 ms in prover time. In this work, we propose an alternative direction with a plausibly post-quantum Blind signature scheme called PoMFRIT. It builds on top of the VOLE-in-the-head Zero-Knowledge proof system (Baum et al. CRYPTO 2023), which we combine with the MAYO digital signature scheme (Beullens, SAC 2021). We implement multiple versions of PoMFRIT to demonstrate security and performance trade-offs, and provide detailed benchmarks of our constructions. Signature issuance requires 0.45 KB communication for Blind signatures of size 6.7 KB. Showing a Blind signature can be done in <76 ms even for a conservative construction with 128 bit security. As a building block for our Blind signature scheme, we implement the first VOLE-in-the-head proof for hash functions in the SHA-3 family, which we consider of independent interest.