Paper 2022/1086

KaLi: A Crystal for Post-Quantum Security using Kyber and Dilithium

Abstract

Quantum computers pose a threat to the security of communications over the internet. This imminent risk has led to the standardization of cryptographic schemes for protection in a post-quantum scenario. We present a design methodology for future implementations of such algorithms. This is manifested using the NIST selected digital signature scheme CRYSTALS-Dilithium and key encapsulation scheme CRYSTALS-Kyber. A unified architecture, \crystal, is proposed that can perform key generation, encapsulation, decapsulation, signature generation, and signature verification for all the security levels of CRYSTALS-Dilithium, and CRYSTALS-Kyber. A unified yet flexible polynomial arithmetic unit is designed that can processes Kyber operations twice as fast as Dilithium operations. Efficient memory management is proposed to achieve optimal latency. \crystal is explicitly tailored for ASIC platforms using multiple clock domains. On ASIC 28nm/65nm technology, it occupies 0.263/1.107 mm$^2$ and achieves a clock frequency of 2GHz/560MHz for the fast clock used for memory unit. On Xilinx Zynq Ultrascale+ZCU102 FPGA, the proposed architecture uses 23,277 LUTs, 9,758 DFFs, 4 DSPs, and 24 BRAMs, at 270 MHz clock frequency. \crystal performs better than the standalone implementations of either of the two schemes. This is the first work to provide a unified design in hardware for both schemes.