A new difference method for side-channel analysis with high-dimensional leakage models

The goal of the DPA contest v2 (2009 - 2010) was to find the most efficient side-channel attack against a particular unprotected AES-128 hardware implementation. In this paper we discuss two problems of general importance that affect the success rate of profiling based attacks, and we provide effective solutions. First, we consider the impact of temperature variations on the power consumption, which causes a so-called drifting offset. To cope with this problem we introduce a new method called Offset Tolerant Method (OTM) and adjust OTM to the stochastic approach (SA-OTM). The second important issue of this paper concerns the choice of an appropriate leakage model as this determines the success rate of SA and SA-OTM. Experiments with high-dimensional leakage models show that the overall leakage is not only caused by independent transitions of bit lines. Compared to the formely best submitted attack of the DPA contest v2 the combination of SA-OTM with high-dimensional lea kage models reduces the required number of power traces to 50%.