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Improved Distinguishers on Stream Ciphers with Certain Weak Feedback Polynomials

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Author

Summary, in English

It is well known that fast correlation attacks can be very efficient if the feedback polynomial is of low weight. These feedback polynomials can be considered weak in the context of stream ciphers. This paper generalizes the class of weak feedback polynomials into polynomials were taps are located in several groups, possibly far apart. Low weight feedback polynomials are thus a special case of this class. For the general class it is shown that attacks can sometimes be very efficient even though the polynomials are of large weight. The main idea is to consider vectors of noise variables. It is shown how the complexity of a distinguishing attack can be efficiently computed and that the complexity is closely related to the minimum row distance of a generator matrix for a convolutional code. Moreover, theoretical results on the size of the vectors are given.

Publishing year

2012

Language

English

Pages

6183-6193

Publication/Series

IEEE Transactions on Information Theory

Volume

58

Issue

9

Document type

Journal article

Publisher

IEEE - Institute of Electrical and Electronics Engineers Inc.

Topic

  • Electrical Engineering, Electronic Engineering, Information Engineering

Keywords

  • correlation attack
  • LFSR
  • stream cipher
  • weak feedback polynomial

Status

Published

Research group

  • Crypto and Security

ISBN/ISSN/Other

  • ISSN: 0018-9448