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Intrinsic statistical weakness of keystream generators

  • Jovan Dj. Golić
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 917)

Abstract

It is shown that an arbitrary binary keystream generator with M bits of memory can be linearly modelled as a non-autonomous linear feedback shift register of length at most M with an additive input sequence of nonbalanced identically distributed binary random variables. An effective method for the linear model determination based on the linear sequential circuit approximation of autonomous finite-state machines is developed. Linear models for clock-controlled shift registers and arbitrary shift register based keystream generators are derived. Several examples including the time-variant memoryless combiner, the basic summation generator, the stop-and-go cascade, and the shrinking generator are presented. Linear models are the basis for a general structure-dependent and initial-state-independent statistical test and they may also be used for correlation attacks on the initial-state. Theoretical security against the introduced statistical attack appears hard to control in practice and hard to achieve with simple schemes.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1995

Authors and Affiliations

  • Jovan Dj. Golić
    • 1
    • 2
  1. 1.Information Security Research CentreQueensland University of TechnologyBrisbaneAustralia
  2. 2.School of Electrical EngineeringUniversity of BelgradeUSA

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