A Lightweight and Efficient BRAM-free NTT Unit for Crystals-Dilithium

During the standardization of post-quantum cryptography by the National Institute of Standards and Technology (NIST), the lattice-based Crystals-Dilithium algorithm was selected as the standardized digital signature scheme. This work designs a lightweight and efficient BRAM-free Number Theoretic Transform (NTT) unit, which is a major bottleneck for Crystals-Dilithium. Firstly, we propose an improved parallel modular multiplication based on the K-RED algorithm, effectively reducing resource consumption and shortening the critical path. Furthermore, a BRAM-free iterative NTT architecture is designed, utilizing three first-in-first-out (FIFO) buffers to store intermediate data. Evaluated on the Xilinx Artix-7 and Zynq UltraScale+ platforms, our proposed NTT architecture presents the best hardware efficiency with less resource consumption. Experimental results show that our design is 36.7%-80.9% reduced in terms of resource consumption and is 31.5%-89.9% better in terms of hardware efficiency compared with state-of- the-art works.