Cryptanalysis of Stream Cipher COS(2, 128) Mode I

Authors:
Hongjun Wu;Feng Bao
Affiliations:
-;-
Venue:
ACISP '02 Proceedings of the 7th Australian Conference on Information Security and Privacy
Year:
2002

Citing 1
Cited 1

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Weaknesses of COSvd (2,128) stream cipher

ICISC'05 Proceedings of the 8th international conference on Information Security and Cryptology

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Abstract

Filiol and Fontaine recently proposed a family of stream ciphers named COS. COS is based on nonlinear feedback shift registers and was claimed to be highly secure. Babbage showed that COS (2, 128) Mode II is extremely weak. But Babbage's attack is very expensive to break the COS (2, 128) Mode I (the complexity is around 252). In this paper, we show that the COS (2, 128) Mode I is very weak. Secret information could be recovered easily with about 216-bit known plaintext.