6 May 2014

Practical complexity cube attacks

Recently, Itai Dinur, Paweł Morawiecki, Josef Pieprzyk, Marian Srebrny and Michał Straus published new attacks on keyed instances of Keccak, i.e., when it is used as a stream cipher or to compute a message authentication code (MAC). The attacks are cube attacks that exploit the low algebraic degree of a primitive and have a data complexity of the order of 2n if this degree is n. Since the round function has algebraic degree 2, the attacks can be applied on 5 or 6 rounds of Keccak-f with a practical complexity.

These attacks are the first ones with practical complexity to reach 6 rounds. Looking at more theoretical complexities, these attacks can most probably reach a few more rounds.