Security Evaluation of a DPA-Resistant S-Box Based on the Fourier Transform

摘要

At CHES 2006, Pfouff et al. proposed a novel S-box calculation based on the discrete Fourier transform as a first-order DPA countermeasure. At CHES 2008, Coron et al. showed that the original countermeasure can be broken by first-order DPA due to a biased mask and they proposed an improved algorithm. This paper shows that there is still a flaw in the Coron's S-box algorithm with respect to a practical software implementation. We pre-process the power traces to separate them into two subgroups, each has a biased mask. For the separated power traces, we propose two post analysis methods to identify the key. One is based on CPA attack against one subgroup, and the other is utilizing the difference of means for two subgroups and a pattern matching. Finally, we compare these two attack methods and propose an algorithm level countermeasure to enhance the security of Coron's S-box.