Paper 2011/652

Security Enhancement of the Vortex Family of Hash Functions

Shay Gueron and Michael Kounavis


Vortex is a new family of one-way hash functions which has been submitted to the NIST SHA-3 competition. Its design is based on using the Rijndael block cipher round as a building block, and using a multiplication-based merging function to support fast mixing in a small number of steps. Vortex is designed to be a fast hash function, when running on a processor that has AES acceleration and has a proven collision resistance [2]. Several attacks on Vortex have been recently published [3, 4, 5, 6] exploiting some structural properties of its design, as presented in the version submitted to the SHA-3 competition. These are mainly ¯rst and second preimage attacks with time complexity below the ideal, as well as attempts to distinguish the Vortex output from random. In this paper we study the root-cause of the attacks and propose few amendments to the Vortex structure, which eliminate the attacks without a®ecting its collision resistance and performance.

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2021-02-16: revised
2011-12-09: received
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      author = {Shay Gueron and Michael Kounavis},
      title = {Security Enhancement of the Vortex Family of Hash Functions},
      howpublished = {Cryptology ePrint Archive, Paper 2011/652},
      year = {2011},
      note = {\url{}},
      url = {}
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