Paper 2013/022

Nonlinear cryptanalysis of reduced-round Serpent and metaheuristic search for S-box approximations.

James McLaughlin and John A. Clark


We utilise a simulated annealing algorithm to find several nonlinear approximations to various S-boxes which can be used to replace the linear approximations in the outer rounds of existing attacks. We propose three variants of a new nonlinear cryptanalytic algorithm which overcomes the main issues that prevented the use of nonlinear approximations in previous research, and we present the statistical frameworks for calculating the complexity of each version. We present new attacks on 11-round Serpent with better data complexity than any other known-plaintext or chosen-plaintext attack, and with the best overall time complexity for a 256-bit key.

Available format(s)
Secret-key cryptography
Publication info
Published elsewhere. Unknown where it was published
Nonlinear cryptanalysisgeneralized linear cryptanalysismetaheuristicssimulated annealingmultidimensional linear cryptanalysisSerpent
Contact author(s)
jmclaugh @ cs york ac uk
2013-01-18: received
Short URL
Creative Commons Attribution


      author = {James McLaughlin and John A.  Clark},
      title = {Nonlinear cryptanalysis of reduced-round Serpent and metaheuristic search for S-box approximations.},
      howpublished = {Cryptology ePrint Archive, Paper 2013/022},
      year = {2013},
      note = {\url{}},
      url = {}
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