New Linear Correlations Related to State Information of RC4 PRGA Using Ⅳ in WPA

摘要

RC4 is a stream cipher designed by Ron Rivest in 1987, and is widely used in various applications. WPA is one of these applications, where TKIP is used for a key generation procedure to avoid weak Ⅳ generated by WEP. In FSE 2014, two different attacks against WPA were proposed by Sen Gupta et al. and Paterson et al. Both focused correlations between the keystream bytes and the first 3 bytes of the RC4 key in WPA. In this paper, we focus on linear correlations between unknown internal state and the first 3 bytes of the RC4 key in both generic RC4 and WPA, where the first 3 bytes of the RC4 key is known in WPA. As a result, we could discover various new linear correlations, and prove these correlations theoretically.