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FIPS PUB 462
Supersedes FIPS PUB 461
1988 January 22
Federal Information
Processing Standards Publication 462
1993 December 30
Announcing the Standard for
DATA ENCRYPTION STANDARD (DES)
(The Foreword, Abstract, and Key Words
can be found at the end of this document.)
Federal Information Processing Standards Publications (FIPS PUBS) are issued by the National Bureau of Standards in
accordance with section 111 (f) (2) of the Federal Property and Administrative Services Act of 1949, as amended, Public
Law 89306 (79 Stat 1127), Executive Order 11717 (38 FR 12315, dated May 11, 1973), and Part 6 of Title 15 Code of
Federal Regulations.
1. Name of Standard.
Data Encryption Standard (DES).
2. Category of Standard.
Computer Security.
3. Explanation.
The Data Encryption Standard (DES) specifies a FIPS approved cryptographic algorithm as
required by FIPS 1401. This publication provides a complete description of a mathematical algorithm for
encrypting (enciphering) and decrypting (deciphering) binary coded information. Encrypting data converts it
to an unintelligible form called cipher. Decrypting 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 randomly generated and used directly
by the algorithm. The other 8 bits, which are not used by the algorithm, are used for error detection. The 8
error detecting bits are set to make the parity of each 8bit byte of the key odd, i.e., there is an odd number of
"1"s in each 8bit byte
1
. Authorized users of encrypted computer data must have the key that was used to
encipher the data in order to decrypt it. The encryption algorithm specified in this standard is commonly
known among those using the standard. The unique key chosen for use in a particular application makes the
results of encrypting data using the algorithm unique. Selection of a different key causes the cipher that is
produced for any given set of inputs to be different. The cryptographic security of the data depends on the
security provided for the key used to encipher and decipher the data.
Data can be recovered from cipher only by using exactly the same key used to encipher it. Unauthorized
recipients of the cipher who know the algorithm but do not have the correct key cannot derive the original
data algorithmically. However, anyone who does have the key and the algorithm can easily decipher the
cipher and obtain the original data. A standard algorithm based on a secure key thus provides a basis for
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View Full Documentexchanging encrypted computer data by issuing the key used to encipher it to those authorized to have the
data.
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