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Second-order Scatter Attack

Second-order analyses have shown a great interest to defeat first level of masking protections. Their practical realization remains tedious in a lot of cases. This is partly due to the difficulties of achieving a fine alignment of two areas that are combined together afterward. Classical protections makes therefore use of random jitter or shuffling to make the alignment difficult or even impossible. This paper extends Scatter attack to high-order analyses. Processing the jointdistribution of two selection of points, it becomes possible to retrieve the secret key even when traces are not fully aligned. The results presented in this paper are validated through practical experimentation and compared with existing window-based techniques, such as the FFT. Scatter shows the best results when misalignment is significant. This illustrates that Scatter offers an alternative to existing high-order attacks and can target all kinds of cryptography implementations, regardless they are executed in hardware or software. With the ability to exploit several leakage points, it may be valuable also when applying a second-order attack on aligned traces.