Security of the Misty Structure beyond the Birthday Bound

Abstract

In this paper, we first prove beyond-birthyday-bound security for the Misty structure. Specifically, we show that an r-round Misty structure is secure against CCA attacks up to O(2(rn/r+7)) query complexity, where n is the size of each round permutation. So for any is an element of > 0, a sufficient number of rounds would guarantee the security of the Misty structure up to 2(n(1-is an element of)) query complexity.