The COS Stream Ciphers are Extremely Weak

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Paper 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 PS
Category: Secret-key cryptography
Publication info: Published elsewhere. Unknown where it was published
Keywords: COS stream cipher nonlinear feedback shift register cryptanalysis
Contact author(s): steve babbage @ vodafone com
History: 2001-09-11: received
Short URL: https://ia.cr/2001/078
License: CC BY