On Apache/1.3.41 (Unix) PHP/5.2.5 mod_perl/1.30 mod_gzip/1.3.26.1a
Under GNU General Public License
2009-01-08 07:38 @38.103.63.58 CrawledBy CCBot/1.0 (+http://www.commoncrawl.org/bot.html)
CRYPT(3) Library functions CRYPT(3)
NAME
crypt - password and data encryption
SYNOPSIS
#define _XOPEN_SOURCE
#include <unistd.h>
char *crypt(const char *key, const char *salt);
DESCRIPTION
crypt is the password encryption function. It is based on the Data Encryption
Standard algorithm with variations intended (among other things) to discourage use
of hardware implementations of a key search.
key is a user’s typed password.
salt is a two-character string chosen from the set [a–zA–Z0–9./]. This string is
used to perturb the algorithm in one of 4096 different ways.
By taking the lowest 7 bits of each of the first eight characters of the key, a
56-bit key is obtained. This 56-bit key is used to encrypt repeatedly a constant
string (usually a string consisting of all zeros). The returned value points to
the encrypted password, a series of 13 printable ASCII characters (the first two
characters represent the salt itself). The return value points to static data
whose content is overwritten by each call.
Warning: The key space consists of 2**56 equal 7.2e16 possible values. Exhaustive
searches of this key space are possible using massively parallel computers. Soft-
ware, such as crack(1), is available which will search the portion of this key
space that is generally used by humans for passwords. Hence, password selection
should, at minimum, avoid common words and names. The use of a passwd(1) program
that checks for crackable passwords during the selection process is recommended.
The DES algorithm itself has a few quirks which make the use of the crypt(3) inter-
face a very poor choice for anything other than password authentication. If you
are planning on using the crypt(3) interface for a cryptography project, don’t do
it: get a good book on encryption and one of the widely available DES libraries.
RETURN VALUE
A pointer to the encrypted password is returned. On error, NULL is returned.
ERRORS
ENOSYS The crypt function was not implemented, probably because of U.S.A. export
restrictions.
GNU EXTENSION
The glibc2 version of this function has the following additional features. If salt
is a character string starting with the three characters "$1$" followed by at most
eight characters, and optionally terminated by "$", then instead of using the DES
machine, the glibc crypt function uses an MD5-based algorithm, and outputs up to 34
bytes, namely "$1$<string>$", where "<string>" stands for the up to 8 characters
following "$1$" in the salt, followed by 22 bytes chosen from the set
[a–zA–Z0–9./]. The entire key is significant here (instead of only the first 8
bytes).
Programs using this function must be linked with -lcrypt.
CONFORMING TO
SVID, X/OPEN, BSD 4.3, POSIX 1003.1-2001
SEE ALSO
login(1), passwd(1), encrypt(3), getpass(3), passwd(5)
2001-12-23 CRYPT(3)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache/1.3.41 (Unix) PHP/5.2.5 mod_perl/1.30 mod_gzip/1.3.26.1a
Under GNU General Public License
2009-01-08 07:38 @38.103.63.58 CrawledBy CCBot/1.0 (+http://www.commoncrawl.org/bot.html)