A New SPA Attack on ECC with Regular Point Multiplication

Elliptic Curve Cryptography (ECC) is becoming widely deployed in embedded cryptographic devices because of the reduced number of key bits. However, the side-channel attacks especially simple side-channel analysis (SPA) can obtain secret keys by measuring power consumption. To resist this attack there appear a number of countermeasures such as Montgomery ladder and double-and-add-always algorithm. This paper proposes a new simple power analysis attack to these countermeasures by distinguishing the conditional subtraction of Montgomery modular multiplication (MMM). Experimental results on smart cards demonstrate that this attack method can retrieve secret keys easily in several seconds using one power trace. Several countermeasures that can resist this kind of SPA attack are also demonstrated in this paper.