Here is an explanation of DES from Wiki: The Data Encryption Standard (DES) is a cipher (a method for encrypting information) selected as an official Federal Information Processing Standard (FIPS) for the United States in 1976, and which has subsequently enjoyed widespread use internationally. The algorithm was initially controversial because of classified design elements, a relatively short key length, and suspicions about a National Security Agency (NSA) backdoor. DES consequently received intense academic scrutiny and motivated the modern understanding of block ciphers and their cryptanalysis.