Paper 2018/1180

Lattice-Based Signature from Key Consensus

Leixiao Cheng, Boru Gong, and Yunlei Zhao

Abstract

Given the current research status in lattice-based cryptography, it is commonly suggested that lattice-based signature could be subtler and harder to achieve. Among them, Dilithium is one of the most promising signature candidates for the post-quantum era, for its simplicity, efficiency, small public key size, and resistance against side channel attacks. The design of Dilithium is based on a list of pioneering works (e.g.,[VL09,VL12,BG14]), and has very remarkable performance by very careful and comprehensive optimizations in implementation and parameter selection. Whether better trade-offs on the already remarkable performance of Dilithium can be made is left in \cite{CRYSTALS} as an interesting open question. In this work, we provide new insights in interpreting the design of Dilithium, in terms of key consensus previously proposed in the literature for key encapsulation mechanisms (KEM) and key exchange (KEX). Based on the deterministic version of the optimal key consensus with noise (OKCN) mechanism, originally developed in [JZ16] for KEM/KEX, we present \emph{signature from key consensus with noise} (SKCN), which could be viewed as generalization and optimization of Dilithium. The construction of SKCN is generic, modular and flexible, which in particular allows a much broader range of parameters for searching better tradeoffs among security, computational efficiency, and bandwidth. For example, on the recommended parameters, compared with Dilithium our SKCN scheme is more efficient both in computation and in bandwidth, while preserving the same level of post-quantum security. In addition, using the same routine of OKCN for both KEM/KEX and digital signature eases (hardware) implementation and deployment in practice, and is useful to simplify the system complexity of lattice-based cryptography in general.