Collision-Based Power Analysis of Modular Exponentiation Using Chosen-Message Pairs

This paper proposes new chosen-message power-analysis attacks against public-key cryptosystems based on modular exponentiation, which use specific input pairs to generate collisions between squaring operations at different locations in the two power traces. Unlike previous attacks of this kind, the new attacks can be applied to all the standard implementations of the exponentiation process: binary (left-to-right and right-to-left), m-ary, and sliding window methods. The SPA countermeasure of inserting dummy multiplications can also be defeated (in some cases) by using the proposed attacks. The effectiveness of the attacks is demonstrated by actual experiments with hardware and software implementations of RSA on an FPGA and the PowerPC processor, respectively. In addition to the new collision generation methods, a high-accuracy waveform matching technique is introduced to detect the collisions even when the recorded signals are noisy and the clock has some jitter.