International Association for Cryptologic Research

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Paper: The COS Stream Ciphers are Extremely Weak

Authors:
Steve Babbage
Download:
URL: http://eprint.iacr.org/2001/078
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Abstract: A new family of very fast stream ciphers called COS (for "crossing over system") has been proposed by Filiol and Fontaine, and seems to have been adopted for at least one commercial standard. In this note we show that the COS ciphers are very weak indeed ? it requires negligible effort to reconstruct the state of the keystream generator from a very small amount of known keystream.
BibTeX
@misc{eprint-2001-11490,
  title={The COS Stream Ciphers are Extremely Weak},
  booktitle={IACR Eprint archive},
  keywords={secret-key cryptography / COS, stream cipher, nonlinear feedback shift register, cryptanalysis},
  url={http://eprint.iacr.org/2001/078},
  note={ steve.babbage@vodafone.com 11576 received 11 Sep 2001},
  author={Steve Babbage},
  year=2001
}