Publications

This page groups papers by year of first publication (which may be a preprint).
You can also view my papers on my 🎓 Google Scholar profile.

[🔍 Show all micro abstracts🙅 Hide all micro abstracts]

2024

Jan Bobolz, Jesus Diaz, Markulf Kohlweiss
Foundations of Anonymous Signatures: Formal Definitions, Simplified Requirements, and a Construction Based on General Assumptions
Financial Crypto 2024   [🔍 micro abstract]  [📄 ePrint]  [📝 blog] An anonymous credential system that can be parameterized with functions that define what user information is revealed at issuance time, at presentation time, and to the inspector. Generalizes group signatures, vanilla anonymous credentials, etc.

Jan Bobolz, Pooya Farshim, Markulf Kohlweiss, Akira Takahashi
The Brave New World of Global Generic Groups and UC-Secure Zero-Overhead SNARKs
TCC 2024   [🔍 micro abstract]  [📄 ePrint] We design a global observable generic group UC functionality (similar to observable global random oracles) and use it to prove Groth16 UC-secure.

2023

Johannes Blömer, Jan Bobolz, Laurens Porzenheim
A Generic Construction of an Anonymous Reputation System and Instantiations from Lattices
Asiacrypt 2023   [🔍 micro abstract]  [📄 ePrint]  [📺 presentation] A step towards post-quantum privacy constructions. Unifying the discrete log and lattice settings in a generic reputation system construction. Instantiated with recent lattice building blocks.

Simon Hemmrich, Jan Bobolz, Daniel Beverungen, Johannes Blömer
Designing Business Reputation Ecosystems — A Method for Issuing and Trading Monetary Ratings on a Blockchain
ECIS 2023   [🔍 micro abstract]  [📄 PDF] Interdisciplinary work CS/economics. Designing a reputation system where you pay for and get paid for ratings. Nice application of deniable zero-knowledge proofs.

2022

Johannes Blömer, Jan Bobolz, Henrik Bröcher
On the impossibility of surviving (iterated) deletion of weakly dominated strategies in rational MPC
TCC 2023   [🔍 micro abstract]  [📄 ePrint]  [📺 presentation] Most known rational multi-party computation protocols are actually weakly dominated (and hence game-theoretically “insecure”).

2021

Jan Bobolz, Fabian Eidens, Raphael Heitjohann, Jeremy Fell
Cryptimeleon: A Library for Fast Prototyping of Privacy-Preserving Cryptographic Schemes
Preprinted   [🔍 micro abstract]  [📄 ePrint]  [🌍 website]  [🐦 tweet] Explaining design decisions and some theory behind our prototyping library. Also contains an implementation-friendly view of Schnorr-style protocols.

Jan Bobolz, Fabian Eidens, Stephan Krenn, Sebastian Ramacher, Kai Samelin
Issuer-Hiding Attribute-Based Credentials
CANS 2021   [🔍 micro abstract]  [📄 ePrint]  [📺 presentation] Efficient construction of anonymous credentials. Allows verifiers to specify a list of acceptable issuers. The verifier does not learn who (from that list) issued the credential.

2020

Jan Bobolz, Fabian Eidens, Stephan Krenn, Daniel Slamanig, Christoph Striecks
Privacy-Preserving Incentive Systems with Highly Efficient Point-Collection
AsiaCCS 2020   [🔍 micro abstract]  [📄 ePrint]  [📺 presentation] An anonymous point collection system, using blind signatures from structure-preserving signatures on equivalence classes for efficient and simple privacy-preserving additive updates. Also features offline double-spending protection, a secure retry mechanism, …

2019

Johannes Blömer, Jan Bobolz, Denis Diemert, Fabian Eidens
Updatable Anonymous Credentials and Applications to Incentive Systems
CCS 2019   [🔍 micro abstract]  [📄 ePrint]  [📺 presentation] An anonymous credential system with a simple privacy-preserving mechanism to update attributes blindly. We use that to build a more efficient anonymous point collection system (updating the point count attribute). Features offline double-spending protection.

2018

Johannes Blömer, Jan Bobolz
Delegatable Attribute-based Anonymous Credentials from Dynamically Malleable Signatures
ACNS 2018   [🔍 micro abstract]  [📄 ePrint]  [📺 presentation] A delegatable anonymous credential system that does not encode the delegation chain. Instead, uses dynamically malleable signatures that allows users to freely change some parts of the attribute vector, and delegate a lesser version of that capabililty to others.

Kai Bemmann, Johannes Blömer, Jan Bobolz, Henrik Bröcher, Denis Diemert, Fabian Eidens, Lukas Eilers, Jan Haltermann, Jakob Juhnke, Burhan Otour, Laurens Porzenheim, Simon Pukrop, Erik Schilling, Michael Schlichtig, Marcel Stienemeier
Fully-Featured Anonymous Credentials with Reputation System
SECPID (ARES workshop) 2018   [🔍 micro abstract]  [📄 ePrint]  [🐦 tweet] An anonymous credential system built by our student project group. We discuss features and note that typical anonymous reputation systems can be built generically from anonymous credentials.

Theses

Efficient Verifier-Local Revocation for Anonymous Credentials
Master’s Thesis. Paderborn University. 2015   [🔍 micro abstract]  [📄 PDF] We build a basic accumulator-based ring signature and use it to generically augment any group signature scheme with verifier-local revocation. Also contains a (naive) security definition for anonymous credentials.

Security Proofs for Pairing-Based Cryptography in the Generic Group Model
Bachelor’s Thesis. Paderborn University. 2013   [🔍 micro abstract]  [📄 PDF] We generalize the BBG uber assumption to work with expressions of the form $g^{1/x}$ and prove it in the generic group model.