Abstract
A new bias is detected in the key scheduling algorithm of RC4 and a novel framework that advantageously combines this new bias with the existing ones is proposed. Using the new bias, a different algorithm is proposed to retrieve the RC4 key given the state table. The new method not only improves the success probability but also provides a more efficient way of calculation in comparison with the previous methods for any key size. The efficiency of the algorithm is demonstrated experimentally. If the key length is 40 bits, the secret key is retrieved with a 99% success rate in 0.007 seconds. The success probability for retrieving the 128 bit RC4 key is also increased significantly. 128-bit key can be retrieved with 3% success rate in 185 seconds and 7.45% success rate in 1572 seconds on a 2.67GHz Intel CPU.
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Akgün, M., Kavak, P., Demirci, H. (2008). New Results on the Key Scheduling Algorithm of RC4. In: Chowdhury, D.R., Rijmen, V., Das, A. (eds) Progress in Cryptology - INDOCRYPT 2008. INDOCRYPT 2008. Lecture Notes in Computer Science, vol 5365. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-89754-5_4
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