TYRCA: A RISC-V Tightly-Coupled Accelerator for Code-Based Cryptography

Post-quantum cryptography (PQC) has garnered significant attention across various communities, particularly with the National Institute of Standards and Technology (NIST) advancing to the fourth round of PQC standardization. One of the leading candidates is Hamming Quasi-Cyclic (HQC), which received a significant update on February 23, 2024. This update, which introduces a classical dense-dense multiplication approach, has no known dedicated hardware implementations yet. The innovative Core-V eXtension InterFace (CV-X-IF) is a communication interface for RISC-V processors that significantly facilitates the integration of new instructions to the Instruction Set Architecture (ISA), through tightly connected accelerators. In this paper, we present a TightlY-coupled accelerator for RISC-V for Code-based cryptogrAphy (TYRCA), proposing the first fully tightly-coupled hardware implementation of the HQC-PQC algorithm, leveraging the CV-X-IF. The proposed architecture is implemented on the Xilinx Kintex-7 FPGA. Experimental results demonstrate that TYRCA reduces the execution time by 94% to 96% for HQC-128, HQC-192, and HQC-256, showcasing its potential for efficient HQC code-based cryptography.