Low latency high throughput Montgomery modular multiplier for RSA cryptosystem

With the advancements of communication technology, security threats are also increasing. RSA is a robust cryptosystem to protect classified information. The efficiency of RSA cryptosystem depends on the efficient execution of Montgomery modular multiplication. A low latency and throughput efficient Montgomery modular multiplier is proposed in this paper. The input and final output of this multiplier are binary, but intermediate input and output are carry-saved i.e. sum and carry bits are stored in separate registers. Sum and carry bits are obtained from the addition of operands using carry-save adder (CSA). Montgomery multipliers require quotient calculation for subsequent iteration. The proposed multiplier computes two subsequent quotients in parallel with carry-save addition. Output of carry-save addition is right shifted by two bits to obtain the next-to-next intermediate output. This calculation also requires integer multiples of the inputs. Computation of next output is skipped. Format conversion of output is performed using a carry look-ahead unit (CLU). CLU along with one cycle of carry save addition is also utilized for pre-computation of integer multiples of inputs. The proposed multiplier is implemented on NEXYS4DDR and VIRTEX VII FPGA and the following result is obtained. NEXYS4DDR: Area (LUT + REG): 38903, Delay: 5.84 ns, Cycles: 1158, Latency: 6.76 mu s, Throughput: 302.96 Mbps. VIRTEX VII: Area (LUT): 16447, Delay: 1.62 ns, Cycles: 1158, Latency: 1.88 mu s, Throughput: 1089.4 Mbps. Results verify the improved area, latency and throughput performance of the proposed work. (C) 2021 Karabuk University. Publishing services by Elsevier B.V.