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Erschienen in:
2008 | OriginalPaper | Buchkapitel
New State Recovery Attack on RC4
verfasst von : Alexander Maximov, Dmitry Khovratovich
Erschienen in: Advances in Cryptology – CRYPTO 2008
Verlag: Springer Berlin Heidelberg
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The stream cipher RC4 was designed by R. Rivest in 1987, and it is a widely deployed cipher. In this paper we analyse the class RC4-
N
of RC4-like stream ciphers, where
N
is the modulus of operations, as well as the length of internal arrays. Our new attack is a state recovery attack which accepts the keystream of a certain length, and recovers the internal state. For the reduced RC4-100, our attack has total complexity of around 2
93
operations, whereas the best previous attack (from Knudsen et al.) needs 2
236
of time.
The complexity of the attack applied to the original RC4-256 depends on the parameters of specific states (patterns), which are in turn hard to discover. Extrapolated parameters from smaller patterns give us the attack of complexity about 2
241
, and it is much smaller than the complexity of the best known previous attack 2
779
. The algorithm of the new attack was implemented and verified on small cases.