The basic DES algorithm can be used for both data encryption and data authentication.Here we will look into the Encryption aspect. I will follow another post with authentication..
Data Encryption: It is easy to see how the DES may be used to encrypt a 64-bit plaintext input to a 64-bit cipher text output, but data are seldom limited to 64bits. In order to use DES in a variety of cryptographic applications, four modes of operation were developed:
- electronic codebook (ECB);
- cipher feedback (CFB);
- cipher block chaining (CBC); and
- output feedback (OFB)
Each mode has itsadvantages and disadvantages.
ECB is excellent for encrypting keys;
CFB is typicallyused for encrypting individual characters; and
OFB is often used for encrypting satellite communications.
Both CBC and CFB can be used to authenticate data. These modes of operation permit the use of DES for interactive terminal to host encryption, cryptographic key encryption for automated key management applications, file encryption,mail encryption, satellite data encryption, and other applications. In fact, it is extremely difficult, if not impossible, to find a cryptographic application where the DES cannot be applied.