Power analysis side channel attacks rely on aligned traces. As a counter-measure, devices can use a jittered clock to misalign the power traces. In this paper we suggest a way to overcome this counter-measure, using an old method of integrating samples over time followed by a correlation attack (Sliding Window CPA). We theoretically re-analyze this general method with characteristics of jittered clocks and show that it is stronger than previously believed. We show that integration of samples over a suitably chosen window size actually amplifies the correlation both with and without jitter—as long as multiple leakage points are present within the window. We then validate our analysis on a new data-set of traces measured on a board implementing a jittered clock. The data-set we collected is public and accessible online. Our experiments show that the SW-CPA attack with a well-chosen window size is very successful against a jittered clock counter-measure and significantly outperforms previous suggestions, requiring a much smaller set of traces to correctly identify the correct key.
CITATION STYLE
Fledel, D., & Wool, A. (2019). Sliding-Window Correlation Attacks Against Encryption Devices with an Unstable Clock. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 11349 LNCS, pp. 193–215). Springer Verlag. https://doi.org/10.1007/978-3-030-10970-7_9
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