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

Hongjun Wu; Feng Bao

Paper 2002/005

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).

Metadata

Available format(s): PS
Category: Secret-key cryptography
Publication info: Published elsewhere. Unknown where it was published
Keywords: stream ciphers cryptanalysis COS
Contact author(s): hongjun @ krdl org sg
History: 2002-01-04: received
Short URL: https://ia.cr/2002/005
License: 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},
      url = {https://eprint.iacr.org/2002/005}
}