A cipher developed by IBM and standardized by the US National Bureau of Standards in 1977. It is a Feistel cipher employing a 64-bit data block and a 56-bit key. The shortness of the key has given rise to much controversy concerning its security.
DES can be used simply as a block cipher, in which case its “mode of operation” is called Electronic Codebook (ECB). The three other NBS-recommended modes of operation are Cipher Block Chaining (CBC), Cipher Feedback (CFB), and Output Feedback (OFB). These increase the security of the system by using DES as a building block in a stream cipher, and differ regarding recovery from possible errors of transmission.
The US National Security Agency announced in 1986 that it would no longer certify the algorithm, so it lapsed as an official standard. It should now properly be called the Data Encryption Algorithm (DEA), although DES remains its most usual name, and it continues to be used despite being regarded as insecure for many purposes since brute-force attacks have become feasible.