Improved Bounds on the Linear Complexity of Keystreams Obtained by Filter Generators

  • Nicholas Kolokotronis
  • Konstantinos Limniotis
  • Nicholas Kalouptsidis
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4990)

Abstract

Binary sequences generated by nonlinearly filtering maximal length sequences with period 2n − 1 are studied in this paper. We focus on the particular class of normal filters and provide improved lower bounds on the linear complexity of generated keystreams. This is achieved by first proving properties of a special class of determinants which are associated to linearized polynomials over finite fields of characteristic 2 and then by applying the above to simplify generalizations of the root presence test.

Keywords

Binary sequences filter functions linear complexity linear feedback shift registers linearized polynomials stream ciphers 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2008

Authors and Affiliations

  • Nicholas Kolokotronis
    • 1
  • Konstantinos Limniotis
    • 1
  • Nicholas Kalouptsidis
    • 1
  1. 1.Department of Informatics and TelecommunicationsNational and Kapodistrian University of AthensAthensGreece

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