Data Encryption Standard DES

The Data Encryption Standard (DES) specifies a FIPS accepted cryptographic algorithm as essential by FIPS 140-1. This publication provides a complete description of a mathematical algorithm for decrypting (deciphering) and encrypting (enciphering) binary coded information. Enciphering data converts it to an unintelligible form called cipher. Deciphering cipher converts the data back to its original form called plaintext. The algorithm described in this standard specifies both enciphering and deciphering operations which are based on a binary number called a key.

A key consists of 64 binary digits ("O"s or "1"s) of which 56 bits are erratically used and generated directly by the algorithm. The other 8 bits, which are not used by the algorithm, are used for error finding. The 8 error detecting bits are set to make the parity of every 8-bit byte of the key odd, i.e., there is an odd number of "1"s in every 8-bit byte1. Approved users of encrypted computer data must have the key that was used to encrypt the data in order to decrypt it. The encryption algorithm particular in this standard is generally known among those using the standard. The unique key chosen for use in a particular application makes the results of enciphering data using the algorithm unique.

Range of a different key causes the cipher that is formed for any known set of inputs to be different. The cryptographic security of the data depends on the security provided for the key used to encrypt and decrypt the data.

Data can be recovered from secret message only by using accurately the same key used to encipher it. Illegal receiver of the secret message who know the algorithm but do not have the correct key cannot obtain the original data algorithmically. Though, anyone who does have the algorithm and the key can easily decode the cipher and obtain the original data. A usual algorithm based on a secure key thus provides a basis for exchanging encrypted computer data by issuing the key used to encipher it to those certified to have the data.

Data that is measured sensitive by the liable authority, data that has a high value, or data that represents a high value should be cryptographically confined if it is susceptible to unauthorized exposé or unnoticed modification during transmission or while in storage. A risk analysis should be performed under the way of a responsible authority to determine potential threats. The costs of providing cryptographic security using these standard as well as substitute methods of provided that this protection and their relevant costs should be projected. An accountable authority then should make a choice, based on these analyses, whether or not to use cryptographic security and this standard.