Security of RC4 Stream Cipher

A Plaintext Recovery Attack on Broadcast RC4
(e.g. the multi session attack of RC4 on SSL/TLS)

We published a first plaintext recovery attack of RC4 in the broadcast setting where same plaintext is encrypted by different user keys at FSE 2013 (earlier than AlFardan-Bernstein-Paterson-Poettering-Schuldt Results).

[1] Takanori ISOBE, Toshihiro OHIGASHI, Yuhei WATANABE, and Masakatu MORII, "Full Plaintext Recovery Attack on Broadcast RC4," Proc. the 20th International Workshop on Fast Software Encryption (FSE 2013), Mar. 10-13, 2013. (Submission deadline: November 12, 2012)
The broadcast setting is easily converted into the multi session setting of SSL/TLS.

Summary of results of our paper is as follows

In addition, we give theoritical reasons why first 255 bytes of the keystream have such strong biases.

Pre-proceedings version of this paper and its slide are available at (paper) and (slide).

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