DES_CRYPT(3) Linux Programmer's Manual DES_CRYPT(3)
des_crypt, ecb_crypt, cbc_crypt, des_setparity, DES_FAILED - fast DES encryption
int ecb_crypt(char *key, char *data, unsigned datalen,
int cbc_crypt(char *key, char *data, unsigned datalen,
unsigned mode, char *ivec);
void des_setparity(char *key);
int DES_FAILED(int status);
ecb_crypt() and cbc_crypt() implement the NBS DES (Data Encryption Standard). These rou-
tines are faster and more general purpose than crypt(3). They also are able to utilize
DES hardware if it is available. ecb_crypt() encrypts in ECB (Electronic Code Book) mode,
which encrypts blocks of data independently. cbc_crypt() encrypts in CBC (Cipher Block
Chaining) mode, which chains together successive blocks. CBC mode protects against inser-
tions, deletions and substitutions of blocks. Also, regularities in the clear text will
not appear in the cipher text.
Here is how to use these routines. The first argument, key, is the 8-byte encryption key
with parity. To set the key's parity, which for DES is in the low bit of each byte, use
des_setparity(). The second argument, data, contains the data to be encrypted or
decrypted. The third argument, datalen, is the length in bytes of data, which must be a
multiple of 8. The fourth argument, mode, is formed by ORing together some things. For
the encryption direction OR in either DES_ENCRYPT or DES_DECRYPT. For software versus
hardware encryption, OR in either DES_HW or DES_SW. If DES_HW is specified, and there is
no hardware, then the encryption is performed in software and the routine returns
DESERR_NOHWDEVICE. For cbc_crypt(), the argument ivec is the 8-byte initialization vector
for the chaining. It is updated to the next initialization vector upon return.
DESERR_NONE No error.
DESERR_NOHWDEVICE Encryption succeeded, but done in software instead of the requested
DESERR_HWERROR An error occurred in the hardware or driver.
DESERR_BADPARAM Bad argument to routine.
Given a result status stat, the macro DES_FAILED(stat) is false only for the first two
These routines are present in libc 4.6.27 and later, and in glibc 2.1 and later.
4.3BSD. Not in POSIX.1-2001.
des(1), crypt(3), xcrypt(3)
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