Cryptology ePrint Archive: Report 2009/238

Attacks on Round-Reduced BLAKE

LI Ji and XU Liangyu

Abstract: BLAKE is a new hash family proposed for SHA-3. The core of compression function reuses the core function of ChaCha. A round-dependent permutation is used as message schedule. BLAKE is claimed to achieve full diffusion after 2 rounds. However, message words can be controlled on the first several founds. By exploiting properties of message permutation, we can attack 2.5 reduced rounds. The results do not threat the security claimed in the specification.

Category / Keywords: hash functions

Date: received 26 May 2009, last revised 27 May 2009

Contact author: ji li at sony com cn

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Version: 20090530:123333 (All versions of this report)

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