Two New Techniques of Side-Channel Cryptanalysis.

We describe two new techniques of side-channel cryptanalysis which we call the impossible collision attack and the multiset collision attack. These are inspired by the state-of-the-art cryptanalytic techniques of impossible differential attacks [BBS99] and partial-function collision attacks [GM00] respectively. Using these techniques on an example of the AES we show that one has to mask all the rounds of a 128-bit key AES in order to prevent such attacks. For example these attacks can be used to break a recent proposal by Schramm et al. [SP06] of high order masking for the AES, since it protects only 3 external rounds. [ABSTRACT FROM AUTHOR]