The function passwd2des() takes a character string passwd of arbitrary length and fills a character array key of length 8. The array key is suitable for use as DES key. It has odd parity set in bit 0 of each byte. Both other functions described here use this function to turn their argument passwd into a DES key.
The xencrypt() function takes the ASCII character string secret given in hex, which must have a length that is a multiple of 16, encrypts it using the DES key derived from passwd by passwd2des(), and outputs the result again in secret as a hex string of the same length.
The xdecrypt() function performs the converse operation.
The functions xencrypt() and xdecrypt() return 1 on success and 0 on error.
These routines are present in libc 4.6.27 and later, and in glibc 2.1 and later.
The prototypes are missing from the abovementioned include file.