cbc_crypt, des_setparity, or ecb_crypt Subroutine

Purpose

Implements Data Encryption Standard (DES) encryption routines.

Library

DES library (libdes.a)

Syntax

# include <des_crypt.h>

int ecb_crypt ( key, data, datalen, mode)

char *key;
char *data;
unsigned datalen;
unsigned mode;

int cbc_crypt(key, data, datalen, mode, ivec)

char *key;
char *data;

unsigned datalen;
unsigned mode;
char ivec;

void des_setparity(key)
char *key;

Description

The ecb_crypt and cbc_crypt subroutines implement DES encryption routines, set by the National Bureau of Standards.

The ecb_crypt subroutine encrypts in ECB (Electronic Code Book) mode, which encrypts blocks of data independently.
The cbc_crypt subroutine encrypts in CBC (Cipher Block Chaining) mode, which chains together successive blocks. CBC mode protects against insertions, deletions, and substitutions of blocks. Also, regularities in the clear text will not appear in the cipher text.
These subroutines are not available for export outside the United States.

Note: The DES library must be installed to use these subroutines.

Parameters

Item	Description
data	Specifies that the data is to be either encrypted or decrypted.
datalen	Specifies the length in bytes of data. The length must be a multiple of 8.
key	Specifies the 8-byte encryption key with parity. To set the parity for the key, which for DES is in the low bit of each byte, use the des_setparity subroutine.
ivec	Initializes the vector for the chaining in 8-byte. This is updated to the next initialization vector upon return.
mode	Specifies whether data is to be encrypted or decrypted. This parameter is formed by logically ORing the DES_ENCRYPT or DES_DECRYPT symbols. For software versus hardware encryption, logically OR the DES_HW or DES_SW symbols. These four symbols are defined in the /usr/include/des_crypt.h file.

Return Values

Item	Description
DESERR_BADPARAM	Specifies that a bad parameter was passed to routine.
DESERR_HWERR	Specifies that an error occurred in the hardware or driver.
DESERR_NOHWDEVICE	Specifies that encryption succeeded, but was done in software instead of the requested hardware.
DESERR_NONE	Specifies no error.

Note: Given the stat variable, for example, which contains the return value for either the ecb_crypt or cbc_crypt subroutine, the DES_FAILED(stat) macro is false only for the DESERR_NONE and DESERR_NOHWDEVICE return values.

Files

Item	Description
/usr/include/des_crypt.h	Defines macros and needed symbols for the mode parameter.