Efficient Cryptography on the RISC-V Architecture

RISC-V is a promising free and open-source instruction set architecture. Most of the instruction set has been standardized and several hardware implementations are commercially available. In this paper we highlight features of RISC-V that are interesting for optimizing implementations of cryptographic primitives. We provide the first optimized assembly implementations of table-based AES, bitsliced AES, ChaCha, and the Keccak-f[1600] permutation for the RV32I instruction set. With respect to public-key cryptography, we study the performance of arbitrary-precision integer arithmetic without a carry flag. We then estimate the improvement that can be gained by several RISC-V extensions. These performance studies also serve to aid design choices for future RISC-V extensions and implementations.