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TitleOn selection of samples in algebraic attacks and a new technique to find hidden low degree equations.
Author(s) Pouyan Sepehrdad, Petr Suvsil, Serge Vaudenay
TypeBook, Chapter in Book, Conference Proceeding
AbstractThe best way of selecting samples in algebraic attacks against block ciphers is not well explored and understood. We introduce a simple strategy for selecting the plaintexts and demonstrate its strength by breaking reduced-round KATAN32 andLBlock. In both cases, we present a practical attack which outperforms previous attempts of algebraic cryptanalysis whose complexities were close to exhaustive search. The attack is based on the selection of samples using cube attack and ElimLin which was presented at FSE’12, and a new technique called Universal Proning. In the case ofLBlock, we break 10 out of 32 rounds. In KATAN32, we break 78 out of 254 rounds. Unlike previous attempts which break smaller number of rounds, we do not guess any bit of the key and we only use structural properties of the cipher to be able to break a higher number of rounds with much lower complexity. We show that cube attacks owe their success to the same properties and therefore, can be used as a heuristic for selecting the samples in an algebraic attack. The performance of ElimLin is further enhanced by the new Universal Proning technique, which allows to discover linear equations that are not found by ElimLin.
Keywordsalgebraic attacks, LBlock, KATAN32, ElimLin, Gröbner basis, cube attack, universal proning
URL http://link.springer.com/chapter/10.1007%2F978-3-319-08344-5_4
PublisherBerlin: Springer
Translation No
Refereed No