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

Hongjun Wu and Feng Bao

##### 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 with high cryptographic strength. Babbage showed that COS $(2,128)$ Mode II is extremely weak. But Babbage's attack is too expensive to break the COS $(2,128)$ Mode I (the complexity is around $2^{52}$). In this paper, we show that the COS $(2,128)$ Mode I is too weak. With about $2^{16}$-bit known plaintext, the secret information could be recovered with small amount of memory and computation time (less than one second on a Pentium IV Processor).

Available format(s)
Category
Secret-key cryptography
Publication info
Published elsewhere. Unknown where it was published
Keywords
stream cipherscryptanalysisCOS
Contact author(s)
hongjun @ krdl org sg
History
Short URL
https://ia.cr/2002/005

CC BY

BibTeX

@misc{cryptoeprint:2002/005,
author = {Hongjun Wu and Feng Bao},
title = {Cryptanalysis of Stream Cipher COS (2,128) Mode I},
howpublished = {Cryptology ePrint Archive, Paper 2002/005},
year = {2002},
note = {\url{https://eprint.iacr.org/2002/005}},
url = {https://eprint.iacr.org/2002/005}
}

Note: In order to protect the privacy of readers, eprint.iacr.org does not use cookies or embedded third party content.