Security of the Misty Structure beyond the Birthday Bound

Jooyoung LEE  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E97-A   No.7   pp.1516-1522
Publication Date: 2014/07/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E97.A.1516
Type of Manuscript: PAPER
Category: Cryptography and Information Security
Keyword: 
misty structure,  blockcipher,  indistinguishability,  pseudorandomness,  coupling,  

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