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  <refentry id="function.mcrypt-generic">
   <refnamediv>
    <refname>mcrypt_generic</refname>
    <refpurpose>This function encrypts data</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>string</type><methodname>mcrypt_generic</methodname>
      <methodparam><type>resource</type><parameter>td</parameter></methodparam>
      <methodparam><type>string</type><parameter>data</parameter></methodparam>
     </methodsynopsis>
    <para>
     This function encrypts data. The data is padded with "<literal>\0</literal>"
     to make sure the length of the data is n * blocksize. This
     function returns the encrypted data. Note that the length
     of the returned string can in fact be longer then the input,
     due to the padding of the data.
    </para>
    <para>
     If you want to store the encrypted data in a database make sure to store
     the entire string as returned by mcrypt_generic, or the string will not
     entirely decrypt properly.  If your original string is 10 characters long
     and the block size is 8 (use
     <function>mcrypt_enc_get_block_size</function> to determine the
     blocksize), you would need at least 16 characters in your database field.
     Note the string returned by <function>mdecrypt_generic</function> will be
     16 characters as well...use <function>rtrim</function>($str, "\0") to
     remove the padding.
    </para>
    <para>
     If you are for example storing the data in a MySQL database remember tha
     varchar fields automatically have trailing spaces removed during
     insertion. As encrypted data can end in a space (ASCII 32), the data will
     be damaged by this removal.  Store data in a tinyblob/tinytext (or
     larger) field instead.
    </para>
    <para>
     The encryption handle should always be initialized with
     <function>mcrypt_generic_init</function> with a key and an IV before
     calling this function. Where the encryption is done, you should free the
     encryption buffers by calling <function>mcrypt_generic_deinit</function>.
     See <function>mcrypt_module_open</function> for an example.
    </para>
    <para>
     See also <function>mdecrypt_generic</function>,
     <function>mcrypt_generic_init</function>, and
     <function>mcrypt_generic_deinit</function>.
    </para>
   </refsect1>
  </refentry>

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