Efficient hardware/software co-design for post-quantum crypto algorithm SIKE on ARM and RISC-V based microcontrollers

Post-quantum cryptography has emerged as a very attractive research topic due to the recent advancements in the development of quantum computers. Among the different available post-quantum public-key algorithms, Supersingular Isogeny Key-Encapsulation (SIKE) has posed a unique design challenge due to its resource intensive arithmetic but is characterized by small key sizes. Existing implementations of SIKE either focus on dedicated accelerators on FPGA platforms or on assembly optimized software implementations on ARM. A full FPGA implementation, though offering low latency and high performance, suffers from the disadvantage of having a large area footprint and a low flexibility. On the other hand, a pure software implementation has lower performance compared to FPGA implementations. In this paper, we propose hardware/software co-design methodologies for SIKE and integrate a redundant number based finite field accelerator into two microcontroller platforms based on ARM and RISC-V. The result shows that our implementation on ARM Cortex-A9 enhanced with a field accelerator offers significant speedup in terms of clock cycles when compared to standalone software implementations on ARM32 and ARM64. Moreover, to show how the communication overhead between processor and accelerator can be mitigated, we integrated the finite field accelerator directly into the core of a RISC-V processor. To the best of our knowledge, this is the first design that applies hardware/software co-design methodologies to implement SIKE on ARM and RISC-V platforms. Our proposed design requires 65500 K clock cycles to execute SIKEp434 on an ARM Cortex-A9 processor. On RISC-V, our proposed design requires only 36900 K clock cycles.