DPA Attack on the Improved Ha-Moon Algorithm

Abstract

The algorithm proposed by Ha and Moon [2] is a countermeasure against power analysis. The Ha-Moon algorithm has two drawbacks in that it requires an inversion and has a right-to-left approach. Recently, Yen, Chen, Moon and Ha improved the algorithm by removing these drawbacks [7]. Their new algorithm is inversion-free, has a left-toright 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 [1, 6]. This paper shows that the improved Ha-Moon algorithm is vulnerable to differential power analysis even if we employ their method in selecting si.