Abstract: The Data Encryption Standard is known as a block cipher technique which means a cryptographic key and an algorithm is applied with a block of data simultaneously rather than one bit at a time. To encrypt a plain textmessage, DES groups it into 64-bit blocks. Each block is enciphered using the secret key into a 64-bit cipher text by means of permutation and substitution.The process involves 16 rounds and can run in four different modes, encrypting blocks individually or making each cipher block dependent on all the previous blocks.

Keywords: DES, cipher text, substitution, encryption.