NAME
crypt,
bcrypt_gensalt, bcrypt
— password hashing
SYNOPSIS
#include
<stdlib.h>
#include <unistd.h>
char *
crypt(const
char *key, const char
*setting);
#include
<pwd.h>
char *
bcrypt_gensalt(u_int8_t
log_rounds);
char *
bcrypt(const
char *key, const char
*salt);
DESCRIPTION
These functions are deprecated in favor of crypt_checkpass(3) and crypt_newhash(3).
The
crypt()
function performs password hashing. Additional code has been added to deter
key search attempts and to use stronger hashing algorithms.
The first argument to
crypt() is
a NUL-terminated string key, typically a user's typed
password. The second, setting, currently supports a
single form. If it begins with a string character
(‘$’) and a number then a different
algorithm is used depending on the number. At the moment
‘$2’ chooses Blowfish hashing; see
below for more information.
Blowfish crypt
The Blowfish version of crypt has 128 bits of salt in order to make building dictionaries of common passwords space consuming. The initial state of the Blowfish cipher is expanded using the salt and the password repeating the process a variable number of rounds, which is encoded in the password string. The maximum password length is 72. The final Blowfish password entry is created by encrypting the string
“OrpheanBeholderScryDoubt”
with the Blowfish state 64 times.
The version number, the logarithm of the number of rounds and the
concatenation of salt and hashed password are separated by the
‘$’ character. An encoded
‘8’ would specify 256 rounds. A valid Blowfish password looks
like this:
“$2b$12$FPWWO2RJ3CK4FINTw0Hi8OiPKJcX653gzSS.jqltHFMxyDmmQ0Hqq”.
The whole Blowfish password string is passed as setting for interpretation.
RETURN VALUES
The function crypt() returns a pointer to
the encrypted value on success, and NULL on
failure.
SEE ALSO
encrypt(1), login(1), passwd(1), blowfish(3), crypt_checkpass(3), getpass(3), passwd(5)
HISTORY
A rotor-based crypt() function appeared in
Version 3 AT&T UNIX. A DES-based
crypt() first appeared in
Version 7 AT&T UNIX.
bcrypt() first appeared in OpenBSD
2.1.
BUGS
The crypt() function returns a pointer to
static data, and subsequent calls to crypt() will
modify the same object.