Cryptanalysis of Double-Block-Length Hash Modes MDC-4 and MJH

Deukjo HONG  Daesung KWON  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E97-A   No.8   pp.1747-1753
Publication Date: 2014/08/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E97.A.1747
Type of Manuscript: PAPER
Category: Cryptography and Information Security
hash function,  hash mode,  collision,  preimage,  MDC-4,  MJH,  

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We give some attacks on the DBL hash modes MDC-4 and MJH. Our preimage attack on the MDC-4 hash function requires the time complexity O(23n/2) for the block length n of the underlying block cipher, which significantly improves the previous results. Our collision attack on the MJH hash function has a time complexity less than 2124 for n=128. Our preimage attack on the the MJH compression function finds a preimage with the time complexity of 2n. It is converted to a preimage attack on the hash function with the time complexity of O(23n/2). As far as we know, any cryptanalytic result for MJH has not been published before. Our results are helpful for understanding the security of the hash modes together with their security proofs.