DES adopted in 1977 by (NIST) National Institute of Slandered and Technology.
In DES data are encrypted in 64 bit block with a key length 56 bits and with output ciphertext 64 bits.
DES has the exact structure of Feistel Cipher but without Initial Permutation (IP) and Inverse Initial Permutation \(IP^{-1}\).
Key generator algorithm The key generator passes through many steps to produces subkeys.
Key generator algorithm take 64 bits key as input,the input key numbered in a table from 1 to 64 as the following:
