ABSTRACT
Block ciphers, which operate on an n-bit block of plaintext (the length of which is a function of the cipher), are some of the most powerful, fastest, and most used cryptosystems in existence. Unlike public-key systems, which obtain their security from a well-known hard mathematical problem, block ciphers are secret key systems based on bit operations, and obtain their strengths from a mixture of non-linear operations, such as substitutions, and permutations.
