On the use of RSA public exponent to improve implementation efficiency and side-channel resistance

Abstract

Since the end of the nineties, cryptographic developers must not only provide fast implementations but they must also take Side-Channel Analysis and Fault Injection into account. From that time, many side-channel and fault countermeasures have been proposed to reach a double goal: provide a high level of security while having the smallest impact on performance and memory consumption. In the particular case of RSA, the knowledge of the public exponent has been used to propose the most efficient fault countermeasure in terms of security and performance. However so far no study has been published which exploits such a variable to improve RSA efficiency and side-channel resistance. In this paper, we fill this gap by proposing an original CRT-RSA implementation which makes use of the knowledge of the public exponent. In particular, we investigate an efficient method using only 4 private key parameters out of 5 and we also propose a free message blinding method to reinforce side-channel resistance. © 2014 Springer International Publishing Switzerland.