Hash 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
- One of the following strings:
- A string of at least two characters that represents the salt, where the first character is not @
(at sign). If this format is used, crypt() returns the result of a call to
r_crypt(), which uses the older DES implementation for hashing.
- A string that uses the format
@digest@X@salt or
@digest,iterations@X@salt,
which specifies the standard PBKDF2 implementation and where:
- digest is either S (use SHA512 digest) or s
(use SHA256 digest).
-
iterations is an optional value that follows the digest character and a comma
that specifies an iterations value to use instead of the default value used in PBKDF2 (4096).
- salt is the Base64-encoded salt value.
For example: @S,8192@X@salt
Library:
liblogin
Use the -l login option to
qcc
to link against this library.
Note:
We've deprecated the version of this function in libc.
You should link against liblogin if your application authenticates users against the
/etc/passwd and /etc/shadow files.
Description:
The crypt() function hashes a password.
It's based on the Data Encryption Standard algorithm,
and also includes code to deter key search attempts.
Note:
This function checks only the first eight characters of key.
The algorithm obtains a 56-bit key by taking the lowest 7 bits of the first eight characters of key.
The 56-bit key is used to repeatedly hash a constant string (usually all zeroes).
For license information, see
“Licensing information”
in Typographical Conventions, Support, and Licensing.
Returns:
A pointer to the 13-character hashed value, or NULL on failure.
The first two characters of the hashed value are the salt itself.
Note:
The return value points to static data that's overwritten by each call to crypt().
Classification:
POSIX 1003.1 XSI
| Safety: |
|
|---|
| Cancellation point |
No |
| Interrupt handler |
No |
| Signal handler |
No |
| Thread |
No |