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DES cryptography software

The Data Encryption Standard (DES) block cipher algorithm was developed in the 1970s as a result of a program by the then US National Bureau of Standards (NBS, now the NIST) to develop a single, standard cryptographic algorithm. The official standard FIPS PUB 46 Data Encryption Standard was first published in 1977. The algorithm described in the standard is known as the Data Encryption Algorithm (DEA).

DEA is a block cipher that encrypts 64-bit blocks of plaintext data using a 64-bit key, of which 56 bits are randomly generated and the remaining 8 bits are ignored by the algorithm but may be used for a parity check.

FIPS 46 was withdrawn in 2004 and so DES may no longer be used to protect US Federal Government information. Data encrypted with DEA can be decrypted by brute force methods in under 20 hours using modern computers. The use of DES is now only permitted only as a component function of TDEA. Triple DES (i.e., TDEA), as specified in ANSI X9.52, Keying Options 1 and 2, is recognized as the only FIPS approved DES algorithm.

Although these documents have been withdrawn as Federally-approved standards, they are still available and are useful sources of information:

Federal Information Processing Standard 46, Data Encryption Standard, FIPS PUB 46-3.
Federal Information Processing Standard 74, Guidelines for Implementing and Using the NBS Data Encryption Standard, FIPS PUB 74.
Federal Information Processing Standard, DES Modes of Operation, FIPS PUB 81.

DES functions available in CryptoSys API

DES_Hex - en/decrypt a hex string in one step
DES_HexMode - en/decrypt a hex string in one step using specified mode (EBC, CBC, CFB, OFB, CTR)
DES_Bytes - en/decrypt a byte array in one step
DES_BytesMode - en/decrypt a byte array in one step using specified mode (ECB, CBC, CFB, OFB, CTR)
DES_File - en/decrypt a file in one step
DES_FileHex - en/decrypt a file using a hex key
DES_Init - initialise the context ready for repeated use
DES_InitHex - initialise the context using hex values ready for repeated use
DES_Update - en/decrypt the next set of data and update the context
DES_UpdateHex - en/decrypt the next set of data in hex and update the context
DES_Final - close and clear the context

See the Des Class for the equivalent .NET methods for C# and VB.NET/2005/8.

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This page last updated 15 August 2025.