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Paper: Improved guess-and-determine and distinguishing attacks on SNOW-V

Authors:
Jing Yang , Department of Electrical and Information Technology, Lund University, Lund, Sweden
Thomas Johansson , Department of Electrical and Information Technology, Lund University, Lund, Sweden
Alexander Maximov , Ericsson Research, Lund, Sweden
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DOI: 10.46586/tosc.v2021.i3.54-83
URL: https://tosc.iacr.org/index.php/ToSC/article/view/9174
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Abstract: In this paper, we investigate the security of SNOW-V, demonstrating two guess-and-determine (GnD) attacks against the full version with complexities 2384 and 2378, respectively, and one distinguishing attack against a reduced variant with complexity 2303. Our GnD attacks use enumeration with recursion to explore valid guessing paths, and try to truncate as many invalid guessing paths as possible at early stages of the recursion by carefully designing the order of guessing. In our first GnD attack, we guess three 128-bit state variables, determine the remaining four according to four consecutive keystream words. We finally use the next three keystream words to verify the correct guess. The second GnD attack is similar but exploits one more keystream word as side information helping to truncate more guessing paths. Our distinguishing attack targets a reduced variant where 32-bit adders are replaced with exclusive-OR operations. The samples can be collected from short keystream sequences under different (key, IV) pairs. These attacks do not threaten SNOW-V, but provide more in-depth details for understanding its security and give new ideas for cryptanalysis of other ciphers.
BibTeX
@article{tosc-2021-31496,
  title={Improved guess-and-determine and distinguishing attacks on SNOW-V},
  journal={IACR Transactions on Symmetric Cryptology},
  publisher={Ruhr-Universit├Ąt Bochum},
  volume={2021, Issue 3},
  pages={54-83},
  url={https://tosc.iacr.org/index.php/ToSC/article/view/9174},
  doi={10.46586/tosc.v2021.i3.54-83},
  author={Jing Yang and Thomas Johansson and Alexander Maximov},
  year=2021
}