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Showing content from https://link.springer.com/chapter/10.1007/978-3-540-89754-5_8 below:

New Collision Attacks against Up to 24-Step SHA-2

Abstract

In this work, we provide new and improved attacks against 22, 23 and 24-step SHA-2 family using a local collision given by Sanadhya and Sarkar (SS) at ACISP ’08. The success probability of our 22-step attack is 1 for both SHA-256 and SHA-512. The computational efforts for the 23-step and 24-step SHA-256 attacks are respectively 211.5 and 228.5 calls to the corresponding step reduced SHA-256. The corresponding values for the 23 and 24-step SHA-512 attack are respectively 216.5 and 232.5 calls. Using a look-up table having 232 (resp. 264) entries the computational effort for finding 24-step SHA-256 (resp. SHA-512) collisions can be reduced to 215.5 (resp. 222.5) calls. We exhibit colliding message pairs for 22, 23 and 24-step SHA-256 and SHA-512. This is the first time that a colliding message pair for 24-step SHA-512 is provided. The previous work on 23 and 24-step SHA-2 attacks is due to Indesteege et al. and utilizes the local collision presented by Nikolić and Biryukov (NB) at FSE ’08. The reported computational efforts are 218 and 228.5 for 23 and 24-step SHA-256 respectively and 243.9 and 253 for 23 and 24-step SHA-512. The previous 23 and 24-step attacks first constructed a pseudo-collision and later converted it into a collision for the reduced round SHA-2 family. We show that this two step procedure is unnecessary. Although these attacks improve upon the existing reduced round SHA-2 attacks, they do not threaten the security of the full SHA-2 family.

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Author information Authors and Affiliations

  1. Indian Statistical Institute, Applied Statistics Unit, 203, B.T. Road, Kolkata, 700108, India

    Somitra Kumar Sanadhya & Palash Sarkar

Editor information Editors and Affiliations

  1. Dept. of Computer Science and Engineering, Indian Institute of Technology, 721 302, Kharagpur, India

    Dipanwita Roy Chowdhury

  2. K.U. Leuven, ESAT/COSIC Kasteelpark, Arenberg 10, B-3001, Leuven-Heverlee, Belgium

    Vincent Rijmen

  3. Department of Computer Science and Engineering, Indian Institute of Technology, 721 302, Kharagpur, India

    Abhijit Das

Copyright information

© 2008 Springer-Verlag Berlin Heidelberg

About this paper Cite this paper

Sanadhya, S.K., Sarkar, P. (2008). New Collision Attacks against Up to 24-Step SHA-2 . In: Chowdhury, D.R., Rijmen, V., Das, A. (eds) Progress in Cryptology - INDOCRYPT 2008. INDOCRYPT 2008. Lecture Notes in Computer Science, vol 5365. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-89754-5_8

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