Cryptology ePrint Archive: Report 2010/607

How to Improve Rebound Attacks

Marķa Naya-Plasencia

Abstract: Rebound attacks are a state-of-the-art analysis method for hash functions. These cryptanalysis methods are based on a well chosen differential path and have been applied to several hash functions from the SHA-3 competition, providing the best known analysis in these cases. In this paper we study rebound attacks in detail and find for a large number of cases that the complexities of existing attacks can be improved.

This is done by identifying problems that optimally adapt to the cryptanalytic situation, and by using better algorithms to find solutions for the differential path. Our improvements affect one particular operation that appears in most rebound attacks and which is often the bottleneck of the attacks. This operation, which varies depending on the attack, can be roughly described as {\em merging} large lists. As a result, we introduce new general purpose algorithms for enabling further rebound analysis to be as performant as possible. We illustrate our new algorithms on real hash functions. More precisely, we demonstrate how to reduce the complexities of the best known analysis on four SHA-3 candidates: JH, Gr\o{}stl, ECHO and {\sc Lane} and on the best known rebound analysis on the SHA-3 candidate Luffa.

Category / Keywords: hash functions, SHA-3 competition, rebound attacks, algorithms

Publication Info: This is the extended version of the article published at CRYPTO 2011

Date: received 26 Nov 2010, last revised 26 May 2011

Contact author: maria naya plasencia at gmail com

Available format(s): PDF | BibTeX Citation

Version: 20110526:185325 (All versions of this report)

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