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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 297028 $ -->
<refentry xml:id="function.mcrypt-module-open" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>mcrypt_module_open</refname>
<refpurpose>Opens the module of the algorithm and the mode to be used</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>resource</type><methodname>mcrypt_module_open</methodname>
<methodparam><type>string</type><parameter>algorithm</parameter></methodparam>
<methodparam><type>string</type><parameter>algorithm_directory</parameter></methodparam>
<methodparam><type>string</type><parameter>mode</parameter></methodparam>
<methodparam><type>string</type><parameter>mode_directory</parameter></methodparam>
</methodsynopsis>
<para>
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. <literal>"twofish"</literal> or is
one of the <constant>MCRYPT_ciphername</constant> constants. The module is closed by calling
<function>mcrypt_module_close</function>.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>algorithm</parameter></term>
<listitem>
<para>
The algorithm to be used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>algorithm_directory</parameter></term>
<listitem>
<para>
The <parameter>algorithm_directory</parameter> and
<parameter>mode_directory</parameter> 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 (<literal>""</literal>), the value set by
the <parameter>mcrypt.algorithms_dir</parameter> or
<parameter>mcrypt.modes_dir</parameter> 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
<filename>/usr/local/lib/libmcrypt</filename>).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mode</parameter></term>
<listitem>
<para>
The mode to be used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mode_directory</parameter></term>
<listitem>
<para>
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Normally it returns an encryption descriptor, or &false; on error.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>mcrypt_module_open</function> examples</title>
<programlisting role="php">
<![CDATA[
<?php
$td = mcrypt_module_open(MCRYPT_DES, '',
MCRYPT_MODE_ECB, '/usr/lib/mcrypt-modes');
$td = mcrypt_module_open('rijndael-256', '', 'ofb', '');
?>
]]>
</programlisting>
</example>
</para>
<para>
The first line in the example above will try to open the <literal>DES</literal> cipher from
the default directory and the <literal>EBC</literal> mode from the directory
<filename>/usr/lib/mcrypt-modes</filename>. 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.
</para>
<para>
<example>
<title>Using <function>mcrypt_module_open</function> in encryption</title>
<programlisting role="php">
<![CDATA[
<?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";
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>mcrypt_module_close</function></member>
<member><function>mcrypt_generic</function></member>
<member><function>mdecrypt_generic</function></member>
<member><function>mcrypt_generic_init</function></member>
<member><function>mcrypt_generic_deinit</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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