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Paper: Rotational Cryptanalysis in the Presence of Constants

Authors:
Tomer Ashur , Dept. Electrical Engineering (ESAT), KU Leuven and iMinds, Leuven
Yunwen Liu , Dept. Electrical Engineering (ESAT), KU Leuven and iMinds, Leuven; College of Science, National University of Defense Technology, Changsha
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DOI: 10.13154/tosc.v2016.i1.57-70
URL: http://tosc.iacr.org/index.php/ToSC/article/view/535
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Abstract: Rotational cryptanalysis is a statistical method for attacking ARX constructions. It was previously shown that ARX-C, i.e., ARX with the injection of constants can be used to implement any function. In this paper we investigate how rotational cryptanalysis is affected when constants are injected into the state. We introduce the notion of an RX-difference, generalizing the idea of a rotational difference. We show how RX-differences behave around modular addition, and give a formula to calculate their transition probability. We experimentally verify the formula using Speck32/64, and present a 7-round distinguisher based on RX-differences. We then discuss two types of constants: round constants, and constants which are the result of using a fixed key, and provide recommendations to designers for optimal choice of parameters.
BibTeX
@article{tosc-2016-28115,
  title={Rotational Cryptanalysis in the Presence of Constants},
  journal={IACR Trans. Symmetric Cryptol.},
  publisher={Ruhr-Universit├Ąt Bochum},
  volume={2016, Issue 1},
  pages={57-70},
  url={http://tosc.iacr.org/index.php/ToSC/article/view/535},
  doi={10.13154/tosc.v2016.i1.57-70},
  author={Tomer Ashur and Yunwen Liu},
  year=2016
}