(PHP 4 >= 4.0.2, PHP 5)
mcrypt_module_open — Opens the module of the algorithm and the mode to be used
$algorithm
, string $algorithm_directory
, string $mode
, string $mode_directory
)
This function opens the module of the algorithm and the mode to be used.
The name of the algorithm is specified in algorithm, e.g. "twofish" or is
one of the MCRYPT_ciphername constants. The module is closed by calling
mcrypt_module_close().
algorithmOne of the MCRYPT_ciphername constants, or the name of the algorithm as string.
algorithm_directory
The algorithm_directory parameter is used to locate
the encryption module. When you supply a directory name, it is used. When
you set it to an empty string (""), the value set by the
mcrypt.algorithms_dir php.ini directive is used. When
it is not set, the default directory that is used is the one that was compiled
into libmcrypt (usually /usr/local/lib/libmcrypt).
modeOne of the MCRYPT_MODE_modename constants, or one of the following strings: "ecb", "cbc", "cfb", "ofb", "nofb" or "stream".
mode_directory
The mode_directory parameter is used to locate
the encryption module. When you supply a directory name, it is used. When
you set it to an empty string (""), the value set by the
mcrypt.modes_dir php.ini directive is used. When
it is not set, the default directory that is used is the one that was compiled-in
into libmcrypt (usually /usr/local/lib/libmcrypt).
Normally it returns an encryption descriptor, or FALSE on error.
Example #1 mcrypt_module_open() Examples
<?php
$td = mcrypt_module_open(MCRYPT_DES, '',
MCRYPT_MODE_ECB, '/usr/lib/mcrypt-modes');
$td = mcrypt_module_open('rijndael-256', '', 'ofb', '');
?>
The first line in the example above will try to open the DES cipher from the default directory and the ECB mode from the directory /usr/lib/mcrypt-modes. The second example uses strings as name for the cipher and mode, this only works when the extension is linked against libmcrypt 2.4.x or 2.5.x.
Example #2 Using mcrypt_module_open() in encryption
<?php
/* Open the cipher */
$td = mcrypt_module_open('rijndael-256', '', 'ofb', '');
/* Create the IV and determine the keysize length, use MCRYPT_RAND
* on Windows instead */
$iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_DEV_RANDOM);
$ks = mcrypt_enc_get_key_size($td);
/* Create key */
$key = substr(md5('very secret key'), 0, $ks);
/* Intialize encryption */
mcrypt_generic_init($td, $key, $iv);
/* Encrypt data */
$encrypted = mcrypt_generic($td, 'This is very important data');
/* Terminate encryption handler */
mcrypt_generic_deinit($td);
/* Initialize encryption module for decryption */
mcrypt_generic_init($td, $key, $iv);
/* Decrypt encrypted string */
$decrypted = mdecrypt_generic($td, $encrypted);
/* Terminate decryption handle and close module */
mcrypt_generic_deinit($td);
mcrypt_module_close($td);
/* Show string */
echo trim($decrypted) . "\n";
?>