ACAC Seminar Abstract

ACAC Seminar Abstract

ACAC Seminars

ACAC Seminar Abstract

Cryptanalysis of FORK-256

Speaker: Krystian Matusiewicz (joint work with T. Peyrin, O. Billet, S. Contini and J. Pieprzyk)
Date, Time: Fri, 09 Mar 2007 11:00

In this talk we present a cryptanalysis of a recently proposed dedicated hash function FORK-256. After a brief description of the function we analyse the step transformation and exhibit some pathological differentials that we use in our attack. We present a simple application of those differentials in a differential path that yields near pseudo-collisions. Next, we discuss a general way of finding high-level differential paths in FORK-256 and show a few particularly interesting ones. We present how to use one of those paths with differences in only one message block to find collisions for the compression function with complexity not exceeding 2^126.6, better than by generic birthday paradox and using only small amount of memory. We show that in practice we can use this method to easily find near-collisions with output differences of weights less than 30. Finally, we discuss some theoretical improvements that reduce this complexity by using precomputed tables of size around 2^64. We also show how to extend the attack to the full function (with the predefined IV).

Link: full paper.

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