Issues of Security with the Oswald-Aigner Exponentiation Algorithm

In smartcard encryption and signature applications, randomized algorithms can be used to increase tamper resistance against attacks based on averaging data-dependent power or EMR variations. Oswald and Aigner describe such an algorithm for point multiplication in elliptic curve cryptography (ECC). Assuming an attacker can identify and distinguish additions and doublings during a single point multiplication, it is shown that the algorithm is insecure for repeated use of the same secret key without blinding of that key. Thus blinding should still be used or great care taken to minimise the differences between point additions and doublings.