Data Encryption Standard (DES) is a 64-bit symmetric block cipher which is used to encrypt data in digital communciation. The inputs are a 64-bit plaintext and 56-bit key (which is usually supported as 64-bit input with parity check bit). Output is a 64-bit ciphertext.
DES encryption algorithm is impelemented in C++ and works as follows: The plaintext and key are provided by variables "palintext" and "key", respectively. The ciphertext is calculated and provided in variable "ciphertext". The DES decryption algoirthm follows exactly the same structure but at the reverse direction, i.e., the ciphertext and key are imputs and plaintext is calculated as output.