J.-P.: Sign change fault attacks on elliptic curve cryptosystems

Abstract. We present a new type of fault attacks on elliptic curve scalar multiplications: Sign Change Attacks. These attacks exploit dierent number representations as they are often employed in modern crypto-graphic applications. Previously, fault attacks on elliptic curves aimed to force a device to output points which are on a cryptographically weak curve. Such attacks can easily be defended against. Our attack produces points which do not leave the curve and are not easily detected. The pa-per also presents a revised scalar multiplication algorithm that protects against Sign Change Attacks