The 74th cryptology session

Dear all;

Salam;

The 74th cryptology session will be held on Sunday 23/Aban/1389 (14/Nov/2010) at 3pm in ISSL.

Speaker : Dr. Shahram Khazaei
Subject  : Linearization Framework for Collision Attacks

Please see the attachment.
Regards,

Linearization Framework for Collision Attacks

Dr. Shahram Khazaei

École Polytechnique Fédérale de Lausanne

Sunday 23/Aban/1389 (14/Nov/2010) at 3pm in Bargh#4

Abstract

In this work, an improved differential cryptanalysis framework for finding collisions in

hash functions is provided. Its principle is based on linearization of compression

functions in order to find low weight differential characteristics as initiated by Chabaud

and Joux. This is formalized and refined however in several ways: for the problem of

finding a conforming message pair whose differential trail follows a linear trail, a

condition function is introduced so that finding a collision is equivalent to finding a

preimage of the zero vector under the condition function. Then, the dependency table

concept shows how much influence every input bit of the condition function has on each

output bit. Careful analysis of the dependency table reveals degrees of freedom that

can be exploited in accelerated preimage reconstruction under the condition function.

These concepts are applied to an in-depth collision analysis of reduced-round versions

of the two SHA-3 candidates CubeHash and MD6, and are demonstrated to give by far

the best currently known collision attacks on these SHA-3 candidates.

1. Shahram Khazaei, Simon Knellwolf, Willi Meier, Deian Stefan: Improved Linear

Differential Attacks on CubeHash. AFRICACRYPT 2010: 407-418.

2. Eric Brier, Shahram Khazaei, Willi Meier, Thomas Peyrin: Linearization Framework

for Collision Attacks: Application to CubeHash and MD6. ASIACRYPT 2009: 560-577.

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Information Systems and Security Lab

http://issl.sharif.edu/

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