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Crypt is a string encoding function (hashing). It is used to encrypt passwords, for example in htaccess password files.

There are different implementations of the crypt function:

Unix Specification

crypt,Single UNIX ® Specification Crypt und Unix Passwörter (de)

crypt in Java

Java Implementations of Unix crypt Javascript crypt

PHP crypt -- One-way string encryption (hashing)

crypt in PHP

crypt() will return an encrypted string using the standard Unix DES-based encryption algorithm or alternative algorithms that may be available on the system. Arguments are a string to be encrypted and an optional salt string to base the encryption on. See the Unix man page for your crypt function for more information.

Multiple encryption types

On systems where the crypt() function supports multiple encryption types, the following constants are set to 0 or 1 depending on whether the given type is available:

CRYPT_STD_DES - Standard DES-based encryption with a two character salt

CRYPT_EXT_DES - Extended DES-based encryption with a nine character salt

CRYPT_MD5 - MD5 encryption with a twelve character salt starting with $1$

CRYPT_BLOWFISH - Blowfish encryption with a sixteen character salt starting with $2$ or $2a$

Note: There is no decrypt function, since crypt() uses a one-way algorithm.


Example 1. crypt() examples

$password = crypt('mypassword'); // let the salt be automatically generated

/* You should pass the entire results of crypt() as the salt for comparing a
   password, to avoid problems when different hashing algorithms are used. (As
   it says above, standard DES-based password hashing uses a 2-character salt,
   but MD5-based hashing uses 12.) */
if (crypt($user_input, $password) == $password) {
   echo "Password verified!";

Example 2. Using crypt() with htpasswd

// Set the password
$password = 'mypassword';

// Get the hash, letting the salt be automatically generated
$hash = crypt($password);

Example 3. Using crypt() with different encryption types
if (CRYPT_STD_DES == 1) {
   echo 'Standard DES: ' . crypt('rasmuslerdorf', 'rl') . "\n";

if (CRYPT_EXT_DES == 1) {
   echo 'Extended DES: ' . crypt('rasmuslerdorf', '_J9..rasm') . "\n";

if (CRYPT_MD5 == 1) {
   echo 'MD5:          ' . crypt('rasmuslerdorf', '$1$rasmusle$') . "\n";

if (CRYPT_BLOWFISH == 1) {
   echo 'Blowfish:    ' . crypt('rasmuslerdorf', '$2a$07$rasmuslerd...........$') . "\n";

The above example will output something similar to:

Standard DES: rl.3StKT.4T8M
Extended DES: _J9..rasmBYk8r9AiWNc
MD5:          $1$rasmusle$rISCgZzpwk3UhDidwXvin0
Blowfish:     $2a$07$rasmuslerd............nIdrcHdxcUxWomQX9j6kvERCFjTg7Ra

See also md5() and the Mcrypt extension. 


Source code to the Unix crypt() function

Using <crypt> on this wiki

You can use this Wiki to encrypt your passwords on the fly:


will return


The CryptExtension

the source for enabling this on Mediawiki is very simple,it just uses the PHP crypt function

# crypt mediawiki extension
# by mutante 18.03.2005

$wgExtensionFunctions[] = "wfCryptExtension";

function wfCryptExtension() {
global $wgParser;
$wgParser->setHook( "crypt", "renderCrypt" );

function renderCrypt( $input ) {

$input = mysql_escape_string($input);

$output=crypt('$input'); //

return $output;

yep,nothing i really had to do by myself. Mutante