In these notes I explain symmetric key additive keystream ciphers, using as an example the cipher RC4. I discuss a number of attack models for this class of ciphers, using attacks on RC4 as examples. I cover a number of attacks on RC4, some of which are effective against implementations of RC4 used in the real world.

In many of today’s computer application needs, faster operation is essential to the efficient implementation of information security algorithm. RC4 has been used as the data encryption algorithm for many applications and protocols including the Wi-Fi, Skype, and Bit Torrent to name a few. Several efficient approaches to the implementation of RC4 have been proposed and we review some of those. M...

RC4-Hash is a variable digest length cryptographic hash function based on the design of the RC4 stream cipher. In this paper, we show that RC4-Hash is not collision resistant. Collisions for any digest length can be found with an expected effort of less than 2 compression function evaluations. This is extended to multicollisions for RC4-Hash. Finding a set of 2 colliding messages has an expecte...

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...

In this paper we analyze the statistical distribution of the keystream generator used by the stream ciphers RC4 and RC4A. Our first result is the discovery of statistical biases of the digraphs distribution of RC4/RC4A generated streams, where digraphs tend to repeat with short gaps between them. We show how an attacker can use these biased patterns to distinguish RC4 keystreams of 2 bytes and ...

RC4 Stream cipher is well known for its simplicity and ease to develop in software. But here, in the proposed design we have heighlighted the modified hardware implémentation of RC4. As RC4 is the most popular stream cipher. The proposed design performs reading and swapping simultaneously in one clock cycle. The proposed design also highlights the adder part which enhances the architecture spee...

RC4 is the most widely deployed stream cipher in software applications. In this paper we describe a major statistical weakness in RC4, which makes it trivial to distinguish between short outputs of RC4 and random strings by analyzing their second bytes. This weakness can be used to mount a practical ciphertext-only attack on RC4 in some broadcast applications, in which the same plaintext is sen...

ABSTRACT In this paper, analysis of a simply modified RC4 algorithm is presented. RC4 is the most widely used stream cipher and it is not considered as a cipher that is strong in security. Many alternatives have been proposed to improve RC4 key generation and pseudo random number generation but the thoughts behind this work is to try out a simple modification of RC4’s PRGA, where we can mention...

RC4 is one of the most widely used ciphers in practical software applications. In this thesis we examine security and design aspects of RC4. First we describe the functioning of RC4 and present previously published analyses. We then present a new cipher, Chameleon which uses a similar internal organization to RC4 but uses different methods. The remainder of the thesis uses ideas from both Chame...