Modified Rc4 Dual Key algorithm based on Irreducible Polynomial

The fears of the computer crimes and the need for privacy of information led to the increased interest in encryption to be a way to hide and protect confidential data. Encryption gives a high degree of security at the lowest cost. The traditional encryption methods cannot give the required degree of security when applied to the computer system. Therefore the new technology uses the principles of traditional encryption methods and Mathematical principles applicable on the computers. The increase in the speed of computers has increased the strength of the attacking techniques for stream cipher which is built according to two ways: (random key generation and XOR operation). At the same time, cryptoanalysis adopted on computers as means to analyze the cryptogram and attacking the encrypted text. The evolution of the speed of computers led to the evolution of the attacking force techniques for encryption, which led to the raise the of the complexity of the algorithms through the use alternative processes for the (XOR) operation and instead of use one bit, use tiny block. This paper proposes a novel approach in modifying Rc4 stream cipher algorithm based on irreducible polynomial by using dual key. to decrypt an encrypted message composed of 8-bit the attacker needs 30*212 probability of keys at minimum, this mean the proposed algorithm will increase the complexity of the algorithm 30 * 24 times.