Cryptanalysis of RC4-like Ciphers

Abstract. RC4, a stream cipher designed by Rivest for RSA Data Security Inc., has found several commercial applications, but little public analysis has been done to date. In this paper, alleged RC4 (hereafter called RC4) is described and existing analysis outlined. The properties of RC4, and in particular its cycle structure, are discussed. Several variants of a basic "tracking" attack are described, and we provide experimental results on their success for scaled-down versions of RC4. This analysis shows that, although the full-size RC4 remains secure against known attacks, keystreams are distinguishable from randomly generated bit streams, and the RC4 key can be recovered if a significant fraction of the full cycle of keystream bits is generated (while recognizing that for a full-size system, the cycle length is too large for this to be practical). The tracking attacks discussed provide a significant improvement over the exhaustive search of the full RC4 keyspace. For exampl...

• Type: Conference
• Year: 1998
• Where: SACRYPT
• Authors: Serge Mister, Stafford E. Tavares
• Keywords: Cryptology, Full-size Rc4, RC4 Key, RC4 Keyspace, SACRYPT 1998