Date Added: Apr 2012
The widespread usage of Internet is providing additional channels for a pirate to easily and quickly distribute the copyrighted digital content. As a result, the protection of content is now receiving a significant amount of consideration and strong security technology is required to protect user's sensitive digital data. Cryptography is recognized as the best method of protecting the data against attacks. The three common cryptographic objects are block-encryption algorithms, public-key algorithms and additive stream ciphers. Block ciphers are designed by using two general principles such as diffusion and confusion. Modern block ciphers consist of four transformations such as substitution transformation, permutation transformation, linear mixing transformation and key-adding transformation.