crypt()

Encrypt a password

Synopsis:

#include <unistd.h>

char * crypt( const char * key, 
              const char * salt );

Arguments:

key: A NUL-terminated string (normally a password typed by a user).
salt: A two-character string chosen from the set [a-zA-Z0-9./]. This function doesn't validate the values for salt, and values outside this range may cause undefined behavior. This string is used to perturb the algorithm in one of 4096 different ways.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

This function is in libc.a, but not in libc.so (in order to save space).

Description:

The crypt() function performs password encryption. It's based on the Data Encryption Standard algorithm, and also includes code to deter key search attempts.

This function checks only the first eight characters of key.

You can obtain a 56-bit key by taking the lowest 7 bits of key. The 56-bit key is used to repeatedly encrypt a constant string (usually all zeroes).

Returns:

A pointer to the 13-character encrypted value, or NULL on failure. The first two characters of the encrypted value are the salt itself.

Classification:

POSIX 1003.1 XSI

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	No
Thread	No

Caveats:

The return value points to static data that's overwritten by each call to crypt().