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Bias in the nonlinear filter generator output sequence

Teo, Sui-Guan, Simpson, Leonie R., & Dawson, Edward (2010) Bias in the nonlinear filter generator output sequence. In Proceedings of International Cryptology Conference 2010, Hotel Equatorial Melaka, Melaka.

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    Abstract

    Nonlinear filter generators are common components used in the keystream generators for stream ciphers and more recently for authentication mechanisms. They consist of a Linear Feedback Shift Register (LFSR) and a nonlinear Boolean function to mask the linearity of the LFSR output. Properties of the output of a nonlinear filter are not well studied. Anderson noted that the m-tuple output of a nonlinear filter with consecutive taps to the filter function is unevenly distributed. Current designs use taps which are not consecutive. We examine m-tuple outputs from nonlinear filter generators constructed using various LFSRs and Boolean functions for both consecutive and uneven (full positive difference sets where possible) tap positions. The investigation reveals that in both cases, the m-tuple output is not uniform. However, consecutive tap positions result in a more biased distribution than uneven tap positions, with some m-tuples not occurring at all. These biased distributions indicate a potential flaw that could be exploited for cryptanalysis.

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    ID Code: 34402
    Item Type: Conference Paper
    Keywords: Stream Ciphers, Boolean functions, Nonlinear filter generator
    Subjects: Australian and New Zealand Standard Research Classification > INFORMATION AND COMPUTING SCIENCES (080000) > COMPUTER SOFTWARE (080300) > Computer System Security (080303)
    Australian and New Zealand Standard Research Classification > INFORMATION AND COMPUTING SCIENCES (080000) > OTHER INFORMATION AND COMPUTING SCIENCES (089900) > Information and Computing Sciences not elsewhere classified (089999)
    Divisions: Past > Schools > Computer Science
    Past > QUT Faculties & Divisions > Faculty of Science and Technology
    Past > Institutes > Information Security Institute
    Copyright Owner: Copyright 2010 2nd International Cryptology Conference
    Deposited On: 09 Sep 2010 08:29
    Last Modified: 01 Mar 2012 00:18

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