New Preimage Attack on MDC-4.
Deukjo Hong, Daesung Kwon · 2012
In this paper, we provide some cryptanalytic results for double-block-length (DBL) hash modes of block ciphers, MDC-4. Our preimage attacks follow the framework of Knudsen et al.’s time/memory trade-off preimage attack on MDC-2. We find how to apply it to our objects. When the block length of the underlying block cipher is n bits, the most efficient preimage attack on MDC-4 requires time and space about 23n/2, which is to be compared to the previous best known preimage attack having time complexity of 27n/4. Additionally, we propose an enhanced version of MDC-4, MDC-4 ∗ based on a simple idea. It is secure against our preimage attack and previous attacks and has the same efficiency as MDC-4.