mcrypt_module_open

Removed-7-2-0

Description

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

Cipher

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 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

Mode

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 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

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.

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 (example only: MD5 is not a good hash algorithm for this) */
    $key = substr(hash('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()
• mcrypt_generic()
• mdecrypt_generic()
• mcrypt_generic_init()
• mcrypt_generic_deinit()