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  <refentry id="function.mcrypt-encrypt">
   <refnamediv>
    <refname>mcrypt_encrypt</refname>
    <refpurpose>Encrypts plaintext with given parameters</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>string</type><methodname>mcrypt_encrypt</methodname>
      <methodparam><type>string</type><parameter>cipher</parameter></methodparam>
      <methodparam><type>string</type><parameter>key</parameter></methodparam>
      <methodparam><type>string</type><parameter>data</parameter></methodparam>
      <methodparam><type>string</type><parameter>mode</parameter></methodparam>
      <methodparam choice="opt"><type>string</type><parameter>iv</parameter></methodparam>
     </methodsynopsis>
    <para>
     <function>mcrypt_encrypt</function> encrypts the data
     and returns the encrypted data.
    </para>
    <para>
     <parameter>Cipher</parameter> is one of the MCRYPT_ciphername
     constants of the name of the algorithm as string.
    </para>
    <para>
     <parameter>Key</parameter> is the key with which the data
     will be encrypted. If it's smaller that the required keysize, it
     is padded with '<literal>\0</literal>'. It is better not to use ASCII strings for
     keys. It is recommended to use the mhash functions to create a key 
     from a string.
    </para>
    <para>
     <parameter>Data</parameter> is the data that will be encrypted
     with the given cipher and mode. If the size of the data is not
     n * blocksize, the data will be padded with '<literal>\0</literal>'. The returned
     crypttext can be larger that the size of the data that is given
     by <parameter>data</parameter>.
    </para>
    <para>
     <parameter>Mode</parameter> is one of the MCRYPT_MODE_modename
     constants of one of "ecb", "cbc", "cfb", "ofb", "nofb" or 
     "stream".
    </para>
    <para>
     The <parameter>IV</parameter> parameter is used for the
     initialisation in CBC, CFB, OFB modes, and in some algorithms
     in STREAM mode. If you do not supply an IV, while it is needed
     for an algorithm, the function issues a warning and uses an
     IV with all bytes set to '<literal>\0</literal>'.
    </para>
    <para>
     <example>
      <title><function>mcrypt_encrypt</function> Example</title>
      <programlisting role="php">
<![CDATA[
<?php
    $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    $key = "This is a very secret key";
    $text = "Meet me at 11 o'clock behind the monument.";
    echo strlen($text) . "\n";

    $crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_ECB, $iv);
    echo strlen($crypttext) . "\n";
?>
]]>
      </programlisting>
      <para>
       The above example will print out:
       <screen>
<![CDATA[
42
64
]]>
       </screen>
      </para>
     </example>
    </para>
    <para>
     See also <function>mcrypt_module_open</function> for a more advanced API
     and an example.
    </para>
   </refsect1>
  </refentry>

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