Paper 2026/794

sigma-rs: A Modular Approach for Keyed-Verification Anonymous Credentials

Lindsey Tulloch, The Tor Project, University of Waterloo

Victor Snyder-Graf, RISC Zero

Ian Goldberg, University of Waterloo

Abstract

We introduce a new software stack in Rust aimed at simplifying constructions and deployments of protocols based on modern anonymous credential systems. The stack, called sigma-rs, through its layered design, abstracts cryptographic complexity while remaining flexible enough to support a range of credential schemes, proofs, and access policies. It emphasizes misuse resistance via type safety, domain separation, and prover-state discipline, and supports side-channel-aware constant-time strategies. We evaluate practicality through re-implementations of Tor’s Lox bridge distribution protocols and of user authentication in the Open Observatory for Network Interference.

Note: Preprint

@misc{cryptoeprint:2026/794,
      author = {Michele Orru and Lindsey Tulloch and Victor Snyder-Graf and Ian Goldberg},
      title = {sigma-rs: A Modular Approach for Keyed-Verification Anonymous Credentials},
      howpublished = {Cryptology {ePrint} Archive, Paper 2026/794},
      year = {2026},
      url = {https://eprint.iacr.org/2026/794}
}