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Paper: Spectral analysis of ZUC-256

Authors:
Jing Yang , Dept. of Electrical and Information Technology, Lund University, Lund, Sweden
Thomas Johansson , Dept. of Electrical and Information Technology, Lund University, Lund, Sweden
Alexander Maximov , Ericsson Research, Lund, Sweden
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DOI: 10.13154/tosc.v2020.i1.266-288
URL: https://tosc.iacr.org/index.php/ToSC/article/view/8565
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Abstract: In this paper we develop a number of generic techniques and algorithms in spectral analysis of large linear approximations for use in cryptanalysis. We apply the developed tools for cryptanalysis of ZUC-256 and give a distinguishing attack with complexity around 2236. Although the attack is only 220 times faster than exhaustive key search, the result indicates that ZUC-256 does not provide a source with full 256-bit entropy in the generated keystream, which would be expected from a 256-bit key. To the best of our knowledge, this is the first known academic attack on full ZUC-256 with a computational complexity that is below exhaustive key search.
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BibTeX
@article{tosc-2020-30274,
  title={Spectral analysis of ZUC-256},
  journal={IACR Transactions on Symmetric Cryptology},
  publisher={Ruhr-Universit├Ąt Bochum},
  volume={2020, Issue 1},
  pages={266-288},
  url={https://tosc.iacr.org/index.php/ToSC/article/view/8565},
  doi={10.13154/tosc.v2020.i1.266-288},
  author={Jing Yang and Thomas Johansson and Alexander Maximov},
  year=2020
}