A stream cipher algorithm based on conventional encryption techniques

摘要

In this paper we present a new word-oriented stream cipher, RAINBOW, based on conventional encryption algorithms. The core of this algorithm is the keystream generator. What is used to generate the pseudo-random keystream is composed of "real key" and "temporal key". The "real key" is just like the key in a block cipher, which is known by two users. But the "temporal key" is generated at the beginning of communication. The "real key" and "temporal key" are blended and divided into two parts. One part is taken as plaintext, the other is treated as the key in a conventional encryption algorithm (such as Triple DES, IDEA and so on). The output of the encryption is a pseudo-random keystream, which is then XOR'ed with the plaintext to generate the ciphertext. Because of the diffusion and confusion of the conventional encryption, the "real key", pseudo-random keystreams, plaintext and ciphertext hold very complex and nonlinear relations. We have performed several detailed security analysis. The cryptanalysis of RAINBOW did not reveal an attack better than exhaustive key search. The speed of this algorithm is as fast as commonly block ciphers.