mcrypt_module_open
(PHP 4 >= 4.0.2)
mcrypt_module_open -- Opens the module of the algorithm
and the mode to be used
Description
resource mcrypt_module_open ( string 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(). Normally it returns an encryption
descriptor, or FALSE on error.
The algorithm_directory and mode_directory are used to
locate the encryption modules. When you supply a directory
name, it is used. When you set one of these to the empty
string (""), the value set by the mcrypt.algorithms_dir
or mcrypt.modes_dir ini-directive is used. When these are
not set, the default directories that are used are the ones
that were compiled in into libmcrypt (usually /usr/local/lib/libmcrypt).
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 EBC 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, used
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";
?>
The first line in the example above will try to open the
DES cipher from the default directory and the EBC 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.
See also mcrypt_module_close(), mcrypt_generic(), mdecrypt_generic(),
mcrypt_generic_init(), and mcrypt_generic_deinit().
