DPA attack on the improved Ha-Moon algorithm

Abstract

The Ha-Moon algorithm [4] is a countermeasure against power analysis using a randomized addition chain. It has two drawbacks in that it requires an inversion and has a right-to-left approach. Recently, Yen et al. improved the algorithm by removing these drawbacks [11], Their new algorithm is inversion-free, has 6, left-to-right approach, and employs a window method. They insisted that their algorithm leads to a more secure countermeasure in computing modular exponentiation against side-channel attacks. This algorithm, however, still has a similar weakness observed in [2, 10]. This paper shows that the improved HaMoon algorithm is vulnerable to differential power analysis even if we employ their method in selecting si.