Paper 2015/145

Observations on the SIMON block cipher family

Stefan Kölbl, Gregor Leander, and Tyge Tiessen


In this paper we analyse the general class of functions underly- ing the Simon block cipher. In particular, we derive efficiently computable and easily implementable expressions for the exact differential and linear behaviour of Simon-like round functions. Following up on this, we use those expressions for a computer aided approach based on SAT/SMT solvers to find both optimal differential and linear characteristics for Simon. Furthermore, we are able to find all characteristics contributing to the probability of a differential for Simon32 and give better estimates for the probability for other variants. Finally, we investigate a large set of Simon variants using different rotation constants with respect to their resistance against differential and linear cryptanalysis. Interestingly, the default parameters seem to be not always optimal.

Note: Updated to the revised version of CRYPTO and supplementary tutorial.

Available format(s)
Publication info
A minor revision of an IACR publication in CRYPTO 2015
SIMONblock cipherdifferential cryptanalysislinear cryptanalysisboolean functions
Contact author(s)
stek @ dtu dk
2015-07-03: last of 2 revisions
2015-02-27: received
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      author = {Stefan Kölbl and Gregor Leander and Tyge Tiessen},
      title = {Observations on the SIMON block cipher family},
      howpublished = {Cryptology ePrint Archive, Paper 2015/145},
      year = {2015},
      note = {\url{}},
      url = {}
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