International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 28 September 2022

David Jacquemin, Ahmet Can Mert, Sujoy Sinha Roy
ePrint Report ePrint Report
Isogeny-based cryptography suffers from a long-running time due to its requirement of a great amount of large integer arithmetic. The Residue Number System (RNS) can compensate for that drawback by making computation more efficient via parallelism. However, performing a modular reduction by a large prime which is not part of the RNS base is very expensive. In this paper, we propose a new fast and efficient modular reduction algorithm using RNS. Our method reduces the number of required multiplications by 40\% compared to RNS Montgomery modular reduction algorithm. Also, we evaluate our modular reduction method by realizing a cryptoprocessor for isogeny-based SIDH key exchange. On a Xilinx Ultrascale+ FPGA, the proposed cryptoprocessor consumes 151,009 LUTs, 143,171 FFs and 1,056 DSPs. It achieves 250 MHz clock frequency and finishes the key exchange for SIDH in 3.8 and 4.9 ms.
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