Crossword puzzle attack on NLS

Cho, Joo Yeon & Pieprzyk, Josef (2006) Crossword puzzle attack on NLS. In Biham, Eli & Youssef, Amr M. (Eds.) Lecture Notes in Computer Science : Selected Areas in Cryptography. Springer, pp. 249-265.

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NLS is one of the stream ciphers submitted to the eSTREAM project. We present a distinguishing attack on NLS by Crossword Puzzle (CP) attack method which is introduced in this paper. We build the distinguisher by using linear approximations of both the non-linear feedback shift register (NFSR) and the nonlinear filter function (NLF). Since the bias of the distinguisher depends on the Konst value, which is a key-dependent word, we present the graph showing how the bias of distinguisher vary with Konst. In result, we estimate the bias of the distinguisher to be around O(2^−30). Therefore, we claim that NLS is distinguishable from truly random cipher after observing O(2^60) keystream words. The experiments also show that our distinguishing attack is successful on 90.3% of Konst among 2^32 possible values. We extend the CP attack to NLSv2 which is a tweaked version of NLS. In result, we build a distinguisher which has the bias of around 2− 48. Even though this attack is below the eSTREAM criteria (2^−40), the security margin of NLSv2 seems to be too low.

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ID Code: 73355
Item Type: Book Chapter
Additional Information: Book Subtitle:
13th International Workshop, SAC 2006, Montreal, Canada, August 17-18, 2006 Revised Selected Papers
DOI: 10.1007/978-3-540-74462-7_18
ISBN: 9783540744610
ISSN: 0302-9743
Divisions: Current > QUT Faculties and Divisions > Science & Engineering Faculty
Deposited On: 04 Jul 2014 00:23
Last Modified: 07 Jul 2014 02:20

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