# Information Security and Cryptography Research Group

## Differential and Invertibility Properties of BLAKE

### Jean-Philippe Aumasson, Jian Guo, Simon Knellwolf, Krystian Matusiewicz, and Willi Meier

FSE, Lecture Notes in Computer Science, Springer, vol. 6147, pp. 318–332, 2010.

BLAKE is a hash function selected by NIST as one of the 14 second round candidates for the SHA-3 Competition. In this paper, we follow a bottom-up approach to exhibit properties of BLAKE and of its building blocks: based on differential properties of the internal function G, we show that a round of BLAKE is a permutation on the message space, and present an efficient inversion algorithm. For 1.5 rounds we present an algorithm that finds preimages faster than in previous attacks. Discovered properties lead us to describe large classes of impossible differentials for two rounds of BLAKE's internal permutation, and particular impossible differentials for five and six rounds, respectively for BLAKE-32 and BLAKE-64. Then, using a linear and rotation-free model, we describe near-collisions for four rounds of the compression function.

## BibTeX Citation

@inproceedings{AJKMM10,
author       = {Jean-Philippe Aumasson and Jian Guo and Simon Knellwolf and Krystian Matusiewicz and Willi Meier},
title        = {Differential and Invertibility Properties of BLAKE},
editor       = {Seokhie Hong and Tetsu Iwata},
booktitle    = {FSE},
pages        = 318--332,
series       = {Lecture Notes in Computer Science},
volume       = 6147,
year         = 2010,
publisher    = {Springer},
}