RVSLH: Acceleration of Postquantum Standard SLH-DSA With Customized RISC-V Processor

Postquantum cryptography (PQC) has developed quickly in response to the rise of quantum computers. The US National Institute of Standards and Technology (NIST) recently released three PQC standards, one of which is the hash-based standard stateless hash-based digital signature standard (SLH-DSA), built on SPHINCS+ selected during the NIST Round 3 submissions. Despite its potential, SLH-DSA’s performance is hindered by inefficient execution in the hash function and extensive memory accesses, with the data dependency of the hash function presenting a notable bottleneck. This brief aims to enhance the efficiency of SHAKE-based SLH-DSA schemes using hardware/software co-design on a customized RISC-V processor. We incorporate tightly coupled hardware units and instructions on RISC-V to expedite SLH-DSA, coupled with memory optimizations to enhance overall performance. The contributions of this brief are twofold. First, our design introduces customized single-instruction-multiple-data (SIMD) instructions and corresponding computation hardware units to accelerate Keccak, the essential operation of SHAKE256. In addition, our design streamlines hash operation memory accesses by reorganizing memory space. The proposed processor’s performance is evaluated on Artix-7 field-programmable gate array (FPGA) and 28-nm technology application-specific integrated circuit (ASIC), demonstrating approximately 15 times acceleration compared with the baseline design. Furthermore, it surpasses recent state-of-the-art works in terms of the performance-power–area product.