Paper 2013/430

Security of the Misty Structure Beyond the Birthday Bound

Jooyoung Lee

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 $O(2^{\frac{rn}{r+7}})$ query complexity, where $n$ is the size of each round permutation. So for any $\epsilon>0$, a sufficient number of rounds would guarantee the security of the Misty structure up to $2^{n(1-\epsilon)}$ query complexity.