Cryptanalysts Representation of Nonlinearly Filtered ML-Sequences

Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 219)


A running key generator consisting of a maximum-length (ML) linear feedback shift register (LFSR) and some nonlinear feedforward state filter function is investigated. It is shown how a cryptanalyst can find an equivalent system in a ciphertext-only attack. The analysis uses a Walsh orthogonal expansion of the state filter function and its relation to the crosscorrelation function (CCF) between the ML-sequence and the produced running key sequence.


Stream Cipher Equivalent System Equivalent Function Walsh Function Plaintext Attack 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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    R.C. Titsworth, “Correlation Properties of Cyclic Sequences”, Thesis, California Inst. of Technology, Pasadena, California, 1962.Google Scholar
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    M.G. Karpovsky, “Finite Orthogonal Series in the Design of Digital Devices”, New York and Jerusalem, Wiley and IVP, 1976.zbMATHGoogle Scholar
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    R.J. Lechner, “Harmonic Analysis of Switching Functions”, in “Recent Developments in Switching Theory”, edited by A. Mukhopadhyay, Academic Press, New York and London, 1971.Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1986

Authors and Affiliations

  1. 1.Institute for Communication TechnologyFederal Institute of TechnologyZurichSwitzerland

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