Paper 2025/1166

Threshold Signatures Reloaded: ML-DSA and Enhanced Raccoon with Identifiable Aborts

Sofía Celi, Brave Research, University of Bristol

Rafael del Pino, PQShield

Thomas Espitau, PQShield

Guilhem Niot, PQShield, Univ Rennes, CNRS, IRISA

Thomas Prest, PQShield

Abstract

Threshold signatures enable multiple participants to collaboratively produce a digital signature, ensuring both fault tolerance and decentralization. As we transition to the post-quantum era, lattice-based threshold constructions have emerged as promising candidates. However, existing approaches often struggle to scale efficiently, lack robustness guarantees, or are incompatible with standard schemes — most notably, the NIST-standard ML-DSA. In this work, we explore the design space of Fiat-Shamir-based lattice threshold signatures and introduce the two most practical schemes to date. First, we present an enhanced TRaccoon-based [DKM+24] construction that supports up to 64 participants with identifiable aborts, leveraging novel short secret-sharing techniques to achieve greater scalability than previous state-of-the-art methods. Second — and most importantly — we propose the first practical ML-DSA-compatible threshold signature scheme, supporting up to 6 users. We provide full implementations and benchmarks of our schemes, demonstrating their practicality and efficiency for real-world deployment as protocol messages are computed in at most a few milliseconds, and communication cost ranges from 10.5 kB to 525 kB depending on the threshold.

Note: This is a preliminary version of our research. This work has been split into two papers that supersede it: - Our contributions on Threshold Raccoon have been unified and extended in ePrint 2026/419. - Our contributions on Threshold ML-DSA are now part of ePrint 2026/013.