An Efficient State Recovery Attack on X-FCSR-256

  • Paul Stankovski
  • Martin Hell
  • Thomas Johansson
Part of the Lecture Notes in Computer Science book series (LNCS, volume 5665)


We describe a state recovery attack on the X-FCSR-256 stream cipher of total complexity at most 257.6. This complexity is achievable by requiring 249.3 output blocks with an amortized calculation effort of at most 28.3 table lookups per output block using no more than 233 table entries of precomputational storage.


stream cipher FCSR X-FCSR cryptanalysis state recovery 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  • Paul Stankovski
    • 1
  • Martin Hell
    • 1
  • Thomas Johansson
    • 1
  1. 1.Dept. of Electrical and Information TechnologyLund UniversityLundSweden

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