Paper 2025/871

Simple and Efficient Lattice Threshold Signatures with Identifiable Aborts

Thomas Espitau, PQShield

Guilhem Niot, PQShield, Univ Rennes, CNRS, IRISA

Thomas Prest, PQShield

Abstract

We introduce simple yet efficient lattice-based threshold signatures with identifiable aborts, secure under the MLWE assumption. Central to our construction are novel Distributed Key Generation with Short Shares (sDKG) protocols over lattices, ensuring short shares, small reconstruction coefficients, and linear evaluation of honest shares. This uniquely realizes the "threshold designer's dream": signature shares double as valid signatures under the corresponding secret key shares. With two concrete instantiations (ramp and replicated secret sharings), our schemes match Threshold Raccoon (del Pino et al. EUROCRYPT 2024)’s compact ~10kB size. Further, we unveil 'Death Star Detection', a new algorithm that enhances identifiable aborts by efficiently spotting short vector adversarial correlations, of interest beyond threshold signatures.

Note: This is a preliminary version of our research. This work is superseded by 2026/419, which unified our approach and extended it to the two-round setting with proactive refresh.