Cryptology ePrint Archive: Report 2013/241

The Perils of Repeating Patterns: Observation of Some Weak Keys in RC4

Joachim Strömbergson and Simon Josefsson

Abstract: We describe some observed trivially weak keys for the stream cipher RC4.

Keys with repeating patterns are found to be key length invariant. The cause of the problem is the simplistic key dependent state permutation in the RC4 initialization.

Category / Keywords: secret-key cryptography / RC4, KSA, weak keys, cryptanalysis, stream cipher, pseudo randomness

Date: received 29 Apr 2013

Contact author: joachim at secworks se

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Version: 20130503:082024 (All versions of this report)

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