Paper 2025/356 Original: eprint.iacr.org/2025/356 ↗

Lattice-based Proof-Friendly Signatures from Vanishing Short Integer Solutions

Abstract

Efficient anonymous credentials are typically constructed by combining proof-friendly signature schemes with compatible zero-knowledge proof systems. Inspired by pairing-based proof-friendly signatures such as Boneh- Boyen (BB) and Boneh-Boyen-Shacham (BBS), we propose a wide family of lattice-based proof-friendly signatures based on variants of the vanishing short integer solution (vSIS) assumption [Cini-Lai-Malavolta, Crypto'23]. In particular, we obtain natural lattice-based adaptions of BB and BBS which, similar to their pairing-based counterparts, admit nice algebraic properties. [Bootle-Lyubashevsky-Nguyen-Sorniotti, Crypto'23] (BLNS) recently proposed a framework for constructing lattice-based proof-friendly signatures and anonymous credentials, based on another new lattice assumption called $\mathsf{ISIS}_f$ parametrised by a fixed function $f$, with focus on $f$ being the binary decomposition. We introduce a generalised $\mathsf{ISIS}_f$ framework, called $\mathsf{GenISIS}_f$, with a keyed and probabilistic function $f$. For example, picking $f_b(\mu) = 1/(b-\mu)$ with key $b$ for short ring element $\mu$ leads to algebraic and thus proof-friendly signatures. To better gauge the robustness and proof-friendliness of $\mathsf{(Gen)}\mathsf{ISIS}_f$, we consider what happens when the inputs to $f$ are chosen selectively (or even adaptively) by the adversary, and the behaviour under relaxed norm checks. While bit decomposition quickly becomes insecure, our proposed function families seem robust.