A Modification on Key Stream Generator for RC4 Algorithm

Abstract

Rivest Cipher 4 (RC4) is one of most common stream cipher, but it experience many problem, such as, there is little combination between the plaintext and cipher-text. For this reason RC4 Cipher is vulnerable to a number of attacks. Thereupon, this paper proposes a new modification of the RC4 to strong it. This achieved by modifying key-stream generator based on linear equation with four state tables for generating random numbers. Key control is used for selecting one state table to apply # operation, then performing forward and backward effects to generate the key-stream that used in encryption and decryption. Being evaluated, the results obtained from the statistical probabilities prove that our proposed algorithm is more complex than the standard algorithm by using different key lengths. Also, our proposed RC4 pass the randomness in most metrics in NIST.