Accelerated RISC-V for Post-Quantum SIKE

In this work, we present a fast and area-efficient software-hardware implementation of the supersingular isogeny key encapsulation (SIKE) mechanism. Our software-hardware design achieves both the flexibility of software as well as the efficient performance of intense computations of hardware. In particular, our implementation takes advantage of new and highly optimized hardware modules for addition, multiplication, and hardware-software control, targeted at Xilinx FPGAs. In conjunction with a small RISC-V processor, we can support all four SIKE parameter sets. On a Virtex-7 FPGA, this implementation occupies 3,492 slices, 78 DSPs, and 29 BRAMs, to perform encapsulation and decapsulation over SIKEp434, SIKEp503, SIKEp610, and SIKEp751 in 14.5, 19.2, 29.8, and 42.7 ms, respectively. Despite supporting all four parameter sets, this design has the best area-time product of all isogeny accelerators in the literature.