Originally developed by IBM under the name of LUCIFER, the American NSA (National Security Agency - the US equivalent of GCHQ) and the National Institute of Standards and Technology played a substantial role in the final stages of developing DES. DES is the most well known and widely used symmetric algorithm in the world. The NIST has re-certified DES every five years and it was last certified in 1993 but NIST have indicated that they would not re-certify DES again, AES (Advanced Encryption Standard) is expected to replace DES.
DES has a 64-bit block size and uses a 56-bit key during encryption. DES is a 16-round Feistel cipher and was originally designed for implementation in hardware. Because it is a single-key cryptosystem, when used for communication both sender and receiver must know the same secret key which can be used to encrypt or decrypt the message. DES can also be used by a single-user, for example to store files on a hard disk securely.
No easy attack on DES has yet been discovered, despite research efforts over many years. There is no feasible way to "break" DES other than an exhaustive search - a process which takes 255 steps on average. However, cryptanalysis methods which rely on knowledge of some of the plaintext have had some success. The consensus of the cryptography community is that, if it is not currently so, DES will soon be insecure. As a result of this as of November of 1998 DES was no longer used by the U.S. Government.
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