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# mcrypt_module_open

(PHP 4 >= 4.0.2, PHP 5)

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().

### Parameters

`algorithm`

  One 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).

`mode`

  One 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).

### Return Values

Normally it returns an encryption descriptor, or `FALSE` on error.

### Examples

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";
?>`

### See Also

- mcrypt_module_close() - Closes the mcrypt module
- mcrypt_generic() - This function encrypts data
- mdecrypt_generic() - Decrypts data
- mcrypt_generic_init() - This function initializes all buffers needed for encryption
- mcrypt_generic_deinit() - This function deinitializes an encryption module

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Mcrypt Functions
PHP Manual