Work with DES algorithm

Development of a program for encryption and signature generation messages (digitally signed) based on symmetric DES encryption algorithm. The program implements two modes work: block encryption and decryption of messages, as well as the formation of a digital signature (SHS). It is required to form the source file with text, then The program generates an encrypted file. Program should provide the ability to decrypt the encrypted file, the result of decryption should be equivalent source file. In Program encryption mode, you must request input from keyboard encryption key. Further, the program asks file name for encryption and file name for recording encrypted information. In the mode of building a digital signature, you must request Enter the encryption key from the keyboard. Next is necessary encrypt message blocks and collapse them into according to the SHS scheme - coupling of cipher blocks.