FatSeal: An Efficient Lattice-based Signature Algorithm

The lattice-based signature schemes are promising quantum-resistant replacements for classical signature schemes based on number theoretical hard problems. An important approach to construct lattice-based signature is utilizing the Fiat-Shamir transform and rejection sampling techniques. There are two Fiat-Shamir signatures among five lattice signature schemes submitted to the post-quantum project initiated by National Institute of Standards and Technology. One of them is called Dilithium, which is based on Module-Learning-With-Errors (MLWE) problem, it features on its simple design in the signing algorithm by using uniform sampling. The Dilithium is built on the generic lattices, to make the size of public key more compact, Dilithium adopts compression technique. On the other hand, schemes using NTRU lattices outperform schemes using generic lattices in efficiency and parameter sizes. This paper devotes to designing an efficient NTRU variant of Dilithium, by combining the advantage of NTRU and uniform rejection sampling, this scheme enjoys a concise structure and gains performance improvement over other lattice-based Fiat-Shamir signature without using extra compression techniques.