RSA with CRT: A New Cost-Effective Solution to Thwart Fault Attacks

Abstract

Fault attacks as introduced by Bellcore in 1996 are still a major threat toward cryptographic products supporting RSA signatures. Most often on embedded devices, the public exponent is unknown, turning resistance to fault attacks into an intricate problem. Over the past few years, several techniques for secure implementations have been published, all of which suffering from inadequacy with the constraints faced by embedded platforms. In this paper, we introduce a novel countermeasure mechanism against fault attacks in RSA signature generation. In the restricted context of security devices where execution time, memory consumption, personalization management and code size are strong constraints, our countermeasure is simply applicable with a low computational complexity. Our method extends to all cryptosystems based on modular exponentiation.