A Survey of Recent Attacks on the Filter Generator

  • Sondre Rønjom
  • Guang Gong
  • Tor Helleseth
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4851)


The filter generator consists of a linear feedback shift register (LFSR) and a Boolean filtering function that combines bits from the shift register to create a key stream. The nonlinear combiner generator employs several (LFSRs) and a Boolean function that combines bit from all the registers to generate the key stream. A new attack on the filter generator has recently been described by Rønjom and Helleseth who also extended the attack to linear feedback shift registers over an extension field GF(2 m ). Some extensions and improvements of the attacks to the filter generator have been given by Rønjom, Gong and Helleseth. The purpose of this paper is to give a short overview of these attacks and to discuss how to extend these attacks to the nonlinear combiner generator.


Boolean function filter generator nonlinear combiner generator m-sequences stream ciphers 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2007

Authors and Affiliations

  • Sondre Rønjom
    • 1
  • Guang Gong
    • 2
  • Tor Helleseth
    • 1
  1. 1.The Selmer Center, Department of Informatics, University of Bergen, PB 7803 N-5020 BergenNorway
  2. 2.Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1Canada

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