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Securing the SHA-1 Algorithm Using Pre-Processing Techniques

This paper explores mechanisms to improve the applicability of the SHA-1 algorithm in areas where adopting a new standard is challenging. The author tests simplified versions of pre-processing techniques against collision-based attacks, evaluating the effectiveness of randomization in reducing the likelihood of collisions/pre-image attacks.

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Securing the SHA-1 Algorithm Using Pre-Processing Techniques

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  1. Securing the SHA-1 Algorithm Using Pre-Processing Techniques Betty Huang Computer Systems Lab 2009-2010

  2. Abstract • Since 2005, collision factors have been found for the SHA-1 algorithm. This paper aims to provide several mechanisms to improve the applicability of the algorithm for areas that are not able to adopt a new standard readily. Authors such as Yiqun Lisa Yin, Michael Szydlo, and various members of the National Institute of Standards and Technology have written about the possibilty of modifying the original input in order to reduce the likelihood of collisions/pre-image attacks, but none have tested extensively on how much the randomization would increase the efforts of decrpytion. I hope to be able to test a (likely simplified) version of the techniques against several sophisticated collision-based attacks.

  3. Background • Purpose of Encryption Algorithms • One-way functions • Message Digest: MD5, SHA family • Block Cipher: DES, Blowfish

  4. Attacks

  5. Procedure • Pre-processing: • Message Whitening • Message Interleaving • Tunnel attacks → finds collisions in MD5 under a minute • Apply tunneling to SHA-1 and SHA-1 with pre-processing, analyze time effort.

  6. SHA-1 Pre-processing Output • Enter string to be converted to SHA-1 hash: helloworld • encryption of original string: 6adfb183 a4a2c94a 2f92dab5 ade762a4 7889a5a1 • whitened string: hel00low00orl00d • encryption of whitened string: b090cfcc 577d3c68 0245c1e2 2830d0e0 db03c949 • interleaved string: hheelllloowwoorrlldd • encryption of interleaving string: 1f9a635d f4a7775f 62f19144 1f6abebc a5186b3e • interleaved AND whitened string: hhe00ell00llo00oww00oor00rll00dd • encryption of whitened + interleaved string: 1b6005b5 6c024c57 99e29eed b53b3dab 4ba87337

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