Fast and secure implementation of modular exponentiation for mitigating fine-grained cache attacks

Abstract

Constant-time technique is of crucial importance to prevent secrets of cryptographic algorithms from leakage by cache attacks. In this paper, we propose Permute-Scatter-Gather, a novel constant-time method for the modular exponentiation that is used in the RSA cryptosystem. On the basis of the scatter-gather design, our method utilizes pseudo-random permutation to obfuscate memory access patterns. Based on this strategy, the resistance against fine-grained cache attacks is ensured, i.e., providing the higher level of security than the existing scatter-gather implementations. Evaluation shows that our method outperforms the OpenSSL library at most 11% in the mainstream Intel processors.