Abstract
RC4 Key Scheduling Algorithm (KSA) uses a secret pseudo-random index j which is dependent on the secret key. Let S N be the permutation after the complete KSA of RC4. It is known that the value of j in round y + 1 can be predicted with high probability from S N [y] for the initial values of y and from \(S^{-1}_N[y]\) for the final values of y. This fact has been exploited in several recent works on secret key recovery from S N . In this paper, we perform extensive analysis of some special sequences of indices corresponding to the j values that leak useful information for key recovery. We present new theoretical results on the probability and the number of such sequences. As an application, we explain a new secret key recovery algorithm that can recover a 16 bytes secret key with a success probability of 0.1409. Our strategy has high time complexity at this point and requires further improvement to be feasible in practice.
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Basu, R., Maitra, S., Paul, G., Talukdar, T. (2009). On Some Sequences of the Secret Pseudo-random Index j in RC4 Key Scheduling. In: Bras-Amorós, M., Høholdt, T. (eds) Applied Algebra, Algebraic Algorithms and Error-Correcting Codes. AAECC 2009. Lecture Notes in Computer Science, vol 5527. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-02181-7_15
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DOI: https://doi.org/10.1007/978-3-642-02181-7_15
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