Highly Optimized Montgomery Multiplier for SIKE Primes on FPGA

New primes were proposed for Supersingular Isogeny Key Encapsulation (SIKE) in NIST standardization process of Round 2 after further cryptanalysis research showed that the security levels of the initial primes chosen were overestimated [1], [2]. In this paper, we develop a highly optimized E _p Montgomery multiplication algorithm and architecture that further utilizes the special form of SIKE prime compared to previous implementations available in the literature. We then implement SIKE for all Round 2 NIST security levels (SIKEp434 for NIST security level 1, SIKEp503 for NIST security level 2, SIKEp610 for NIST security level 3, and SIKEp751 for NIST security level 5) on Xilinx Virtex 7 using the proposed multiplier. Our best implementation (NIST security level 1) runs 29% faster and occupies 30% less hardware resources in comparison to the leading counterpart available in the literature [3] and implementations for other security levels achieved similar improvement.