Paper 2009/184

Cryptanalysis of Dynamic SHA(2)

Jean-Philippe Aumasson, Orr Dunkelman, Sebastiaan Indesteege, and Bart Preneel


In this paper, we analyze the hash functions Dynamic SHA and Dynamic SHA2, which have been selected as first round candidates in the NIST hash function competition. These hash functions rely heavily on data-dependent rotations, similar to certain block ciphers, e.g., RC5. Our analysis suggests that in the case of hash functions, where the attacker has more control over the rotations, this approach is less favorable than in block ciphers. We present practical, or close to practical, collision attacks on both Dynamic SHA and Dynamic SHA2. Moreover, we present a preimage attack on Dynamic SHA that is faster than exhaustive search.

Note: Typo fixed in one equation.

Available format(s)
Secret-key cryptography
Publication info
Published elsewhere. Accepted to SAC 2009
hash functionspreimagecollisionSHA-3
Contact author(s)
jeanphilippe aumasson @ gmail com
2009-08-27: last of 5 revisions
2009-05-02: received
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Creative Commons Attribution


      author = {Jean-Philippe Aumasson and Orr Dunkelman and Sebastiaan Indesteege and Bart Preneel},
      title = {Cryptanalysis of Dynamic SHA(2)},
      howpublished = {Cryptology ePrint Archive, Paper 2009/184},
      year = {2009},
      note = {\url{}},
      url = {}
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