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Collisions and other Non-Random Properties for Step-Reduced SHA-256. Cryptology eprint Archive, April 2008. Available at http://eprint.iacr
| Citations: | 18 - 5 self |
BibTeX
@MISC{Indesteege_collisionsand,
author = {Sebastiaan Indesteege and Florian Mendel and Bart Preneel and Christian Rechberger},
title = {Collisions and other Non-Random Properties for Step-Reduced SHA-256. Cryptology eprint Archive, April 2008. Available at http://eprint.iacr},
year = {}
}
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Abstract
Abstract. We study the security of step-reduced but otherwise unmodified SHA-256. We show the first collision attacks on SHA-256 reduced to 23 and 24 steps with complexities 2 18 and 2 28.5, respectively. We give example colliding message pairs for 23-step and 24-step SHA-256. The best previous, recently obtained result was a collision attack for up to 22 steps. We extend our attacks to 23 and 24-step reduced SHA-512 with respective complexities of 2 44.9 and 2 53.0. Additionally, we show nonrandom behaviour of the SHA-256 compression function in the form of free-start near-collisions for up to 31 steps, which is 6 more steps than the recently obtained non-random behaviour in the form of a free-start near-collision. Even though this represents a step forwards in terms of cryptanalytic techniques, the results do not threaten the security of applications using SHA-256. Keywords: SHA-256, SHA-512, hash functions, collisions, semi-freestart collisions, free-start collisions, free-start near-collisions.
Keyphrases
non-random property step-reduced sha-256 cryptology eprint archive free-start near-collisions step forward first collision attack hash function 24-step sha-256 free-start collision respective complexity unmodified sha-256 sha-256 compression function semi-freestart collision cryptanalytic technique nonrandom behaviour non-random behaviour free-start near-collision collision attack example colliding message pair
