ABSTRACT
To enhance the security of symmetric key algorithms, Calude Shannon introduced two principles: confusion and diffusion [2]. He argued that these principles should be followed to design any secure cryptographic system. They are detailed below:
• Confusion: Shannon said confusion makes the relation between the key and the ciphertext as complex as possible. Actually, every character in the key influences every other character of the ciphertext block. This relationship needs to be loosened in such a way that even though the attacker gets some grip on the statistics of the ciphertext, he or she may not be able to deduce the key. A good confusion could be achieved if each character of the ciphertext depends on several parts of the key. For any attacker, it must appear that this dependence is random. This could be achieved by utilizing complex substitution techniques in the algorithm.
