The COS Stream Ciphers are Extremely Weak

Steve Babbage

Paper 2001/078 Original: eprint.iacr.org/2001/078 ↗

The COS Stream Ciphers are Extremely Weak

Steve Babbage

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.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: Preprint.
History: 2001-09-11: last updated; 2001-09-11: published
Short URL: https://ia.cr/2001/078
License: https://creativecommons.org/licenses/by/4.0/

BibTeX

@misc{cryptoeprint:2001/078,
      author = {Steve Babbage},
      title = {The COS Stream Ciphers are Extremely Weak},
      howpublished = {Cryptology {ePrint} Archive, Paper 2001/078},
      year = {2001},
      url = {https://eprint.iacr.org/2001/078}
}