Introduction to DES. The DES mean Data Encryption Standard . It is one of the earliest and most influential symmetric key block ciphers. It was developed by IBM in the early 1970s and later standardized by the U.S. National Institute of Standards and Technology (NIST) in 1977. DES played a foundational role in modern cryptography, serving as the standard encryption method for sensitive data for decade . Data Encryption Standard (DES) Overview Mechanism · DES is an iterative algorithm. For each block of plaintext, encryption is handled in 16 rounds which all perform the identical operation. • In every round a different subkey is used and all subkeys ki are derived from the main key k. Here we consider the following two structures. 1.The Fiestel Structure of DES 2. Internal Structure of DES 1.The Fiestel Structure of DES Data Encryption Standard (DES) structure is a Feistel network. Feistel networks are used in many, but certainly not in all, modern block ciphers...