Methods of security need to be improved to face new techniques of data stealing. The substitution table is the core of the block ciphers encryption and its good design increases the encryption algorithm security. This paper proposes two algorithms to generate modified S-Boxes; the key and plaintext dependent S-Box using RC4 algorithmand using RC4 chaotic algorithm. This paper aims to demonstrate the efficiency of the proposed S-Boxes compared to the existing AES and Dynamic S-Boxes.