Impossible Differentials in Twofish

N. Ferguson

Twofish Technical Report #5, October 5, 1999

ABSTRACT: We show how an impossible-differential attack, first applied to DEAL by Knudsen, can be applied to Twofish. This attack breaks six rounds of the 256-bit key version using 2256 steps; it cannot be extended to seven or more Twofish rounds.

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