DES
The Data Encryption Standard is a NIST standard secret key cryptography method that uses a 56-bit key. DES is based
on an IBM algorithm that was further developed by the U.S. National Security
Agency (NSA). It uses the block cipher method that breaks the text into 64-bit
blocks before encrypting them. There are several DES encryption modes. The most
popular mode exclusive ORs each plaintext block with the previous encrypted block.
DES decryption is very fast and widely used. The secret key may be kept a
total secret and used over again. Or, a key can be randomly generated for each
session, in which case the new key is transmitted to the recipient using a public
key cryptography method such as RSA.
Triple DES is an enhancement to DES that provides considerably more security
than standard DES, which uses only one 56-bit key. There are several Triple DES
methods. EEE3 uses 3 keys and encrypts 3 times. EDE3 uses 3 keys to encrypt,
decrypt, and encrypt again. EEE2 and EDE2 are similar to EEE3 and EDE3, except
that only 2 keys are used, and the first and third operations use the same key.