Improving MDC-4 to Be More Secure

Deukjo HONG  Dong-Chan KIM  Daesung KWON  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E102-A   No.1   pp.278-289
Publication Date: 2019/01/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E102.A.278
Type of Manuscript: PAPER
Category: Cryptography and Information Security
MDC-4+,  collision resistance,  preimage resistance,  

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MDC-4 is the enhanced version of MDC-2, which is a well-known hash mode of block ciphers. However, it does not guarantee sufficient securities required for a cryptographic hash function. In the ideal cipher model, the MDC-4 compression function has the collision security bound close to 25n/8 and the preimage security bound close to 25n/4, where the underlying block cipher has the block size of n bits. We have studied how to improve MDC-4 with simple modification to strengthen its security. It is meaningful work because users often want to improve their familiar systems with low cost. In this paper, we achieve it by proposing MDC-4+, which is a light variation of MDC-4. We prove that MDC-4+ is much more secure than MDC-4 by showing that it has the collision security bound close to optimal 2n and the preimage security bound close to 24n/3. We also discuss its efficiency by comparing existing hash modes.