RC4 stream cipher is one of the most significant symmetric cryptosystems, it is simple and used in many commercial products. RC4 uses dynamic permutations and avoids using Linear Feed Back Shift Register (LFSR). It has many weaknesses, such as the tendency in the generated key stream that some key bytes are biased toward different values. This paper presents a new algorithm using S-box of Advanced Encryption Standard (AES) to solve the correlation between public known outputs of the internal

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... te. The state table is filled from S-box values and additional swapping operations are used. The analysis of the proposed algorithm over variable key length produces key byte streams that have no single and double bias. This paper obtains a new algorithm that combines the efficiency of the RC4 and robustness of AES. The results show that the sequences that are generated by the developed RC4 are more random than the sequence that was generated by the RC4. Also, the developed algorithm demands little time more than RC4 execution time. Additionally, the developed algorithm is robust against most attacks, such as distinguishing attack and can be used in different protocols such as Secure Sockets Layer (SSL) Protocol, Oracle Secure SQL, and Wired Equivalent Privacy (WEP) Protocol.