php-doc-en/functions/mcrypt.xml

 <reference id="ref.mcrypt">
  <title>Mcrypt Encryption Functions</title>
  <titleabbrev>mcrypt</titleabbrev>
  
  <partintro>
   <para>
    These functions work using <ulink
    url="&url.mcrypt;">mcrypt</ulink>.
   </para>
   <para>
    This is an interface to the mcrypt library, which supports a wide
    variety of block algorithms such as DES, TripleDES, Blowfish
    (default), 3-WAY, SAFER-SK64, SAFER-SK128, TWOFISH, TEA, RC2 and
    GOST in CBC, OFB, CFB and ECB cipher modes. Additionally, it
    supports RC6 and IDEA which are considered "non-free".
   </para>
   <para>
    If you linked against libmcrypt 2.4.x, the following additional
    block algorithms are supported: CAST, LOKI97, RIJNDAEL, SAFERPLUS,
    SERPENT and the following stream ciphers: ENIGMA (crypt), PANAMA,
    RC4 and WAKE. With libmcrypt 2.4.x another cipher mode is also
    available; nOFB.
   </para>
   <para>
    To use it, download libmcrypt-x.x.tar.gz from <ulink
    url="&url.mcrypt;">here</ulink> and follow the included
    installation instructions. You need to compile PHP with the
    <option role="configure">--with-mcrypt</option> parameter to
    enable this extension. Make sure you compile libmcrypt with the
    option <option role="configure">--disable-posix-threads</option>.
   </para>
   <para>
    Mcrypt can be used to encrypt and decrypt using the above
    mentioned ciphers. If you linked against libmcrypt-2.2.x, the
    four important mcrypt commands (<function>mcrypt_cfb</function>,
    <function>mcrypt_cbc</function>, <function>mcrypt_ecb</function>,
    and <function>mcrypt_ofb</function>) can operate in both modes
    which are named MCRYPT_ENCRYPT and MCRYPT_DECRYPT, respectively.
    <example>
     <title>Encrypt an input value with TripleDES in ECB mode</title>
     <programlisting role="php">
&lt;?php
$key = "this is a very secret key";
$input = "Let us meet at 9 o'clock at the secret place.";

$encrypted_data = mcrypt_ecb (MCRYPT_TripleDES, $key, $input, MCRYPT_ENCRYPT);
?&gt;
     </programlisting>
    </example>
    This example will give you the encrypted data as a string in
    <literal>$encrypted_data</literal>.
   </para>
   <para>
    If you linked against libmcrypt 2.4.x, these functions are still
    available, but it is recommended that you use the advanced functions.
    <example>
     <title>Encrypt an input value with TripleDES in ECB mode</title>
     <programlisting role="php">
&lt;?php
$key = "this is a very secret key";
$input = "Let us meet at 9 o'clock at the secret place.";

$td = mcrypt_open_module (MCRYPT_TripleDES, "", MCRYPT_MODE_ECB);
$iv = mcrypt_create_iv (mcrypt_enc_get_iv_size ($td), MCRYPT_RAND);
mcrypt_generic_init ($td, $key, $iv);
$encrypted_data = mcrypt_generic ($td, $input);
mcrypt_generic_end ($td);
?&gt;
     </programlisting>
    </example>
    This example will give you the encrypted data as a string in
    <literal>$encrypted_data</literal>.
   </para>
   <para>
    Mcrypt can operate in four block cipher modes (CBC, OFB, CFB, and
    ECB). If linked against libmcrypt-2.4.x mcrypt can also operate
    in the block cipher mode nOFB and in STREAM mode. Then there are
    also constants in the form MCRYPT_MODE_mode for use with several
    functions. We will outline the normal use for each of these modes.
    For a more complete reference and discussion see 
    &book.applied.cryptography;.
    <itemizedlist>
     <listitem>
      <simpara>
       ECB (electronic codebook) is suitable for random data, such as
       encrypting other keys. Since data there is short and random,
       the disadvantages of ECB have a favorable negative
       effect.
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       CBC (cipher block chaining) is especially suitable for
       encrypting files where the security is increased over ECB
       significantly.
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       CFB (cipher feedback) is the best mode for encrypting byte
       streams where single bytes must be encrypted.
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       OFB (output feedback, in 8bit) is comparable to CFB, but
       can be used in applications where error propagation cannot
       be tolerated. It's insecure (because it operates in 8bit
       mode) so it is not recommended to use it.
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       nOFB (output feedback, in nbit) is comparable to OFB, but
       more secure because it operates on the block size of the
       algorithm.
      </simpara>
     </listitem> 
     <listitem>
      <simpara>
       STREAM is an extra mode to include some stream algorithms
       like WAKE or RC4.
      </simpara>
     </listitem> 
    </itemizedlist>
   </para>
   <para>
    PHP does not support encrypting/decrypting bit streams
    currently. As of now, PHP only supports handling of strings.
   </para>
   <para>
    For a complete list of supported ciphers, see the defines at the
    end of <filename>mcrypt.h</filename>. The general rule with the
    mcrypt-2.2.x API is that you can access the cipher from PHP with
    MCRYPT_ciphername. With the mcrypt-2.4.x API these constants also
    work, but it is possible to specify the name of the cipher as
    a string with a call to <function>mcrypt_open_module</function>.
   </para>
   <para>
    Here is a short list of ciphers which are currently supported by
    the mcrypt extension. If a cipher is not listed here, but is
    listed by mcrypt as supported, you can safely assume that this
    documentation is outdated.
    <itemizedlist>
     <listitem>
      <simpara>
       MCRYPT_ARCFOUR_IV (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_ARCFOUR (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_BLOWFISH
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_CAST_128
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_CAST_256
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_CRYPT
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_DES
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_DES_COMPAT (libmcrypt 2.2.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_ENIGMA (libmcrypt 2.4.x only, alias for MCRYPT_CRYPT)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_GOST
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_IDEA (non-free)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_LOKI97 (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_MARS (libmcrypt 2.4.x only, non-free)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_PANAMA (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_RIJNDAEL_128 (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_RIJNDAEL_192 (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_RIJNDAEL_256 (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_RC2
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_RC4 (libmcrypt 2.2.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_RC6 (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_RC6_128 (libmcrypt 2.2.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_RC6_192 (libmcrypt 2.2.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_RC6_256 (libmcrypt 2.2.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_SAFER64
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_SAFER128
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_SAFERPLUS (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_SERPENT (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_SERPENT_128 (libmcrypt 2.2.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_SERPENT_192 (libmcrypt 2.2.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_SERPENT_256 (libmcrypt 2.2.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_SKIPJACK (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_TEAN (libmcrypt 2.2.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_THREEWAY
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_TRIPLEDES
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_TWOFISH (for older mcrypt 2.x versions, or mcrypt 2.4.x )
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_TWOFISH128 (TWOFISHxxx are available in newer 2.x versions, but not in the 2.4.x versions)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_TWOFISH192
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_TWOFISH256
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_WAKE (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       MCRYPT_XTEA (libmcrypt 2.4.x only)
      </simpara>
     </listitem>
    </itemizedlist>
   </para>
   <para>
    You must (in CFB and OFB mode) or can (in CBC mode) supply an
    initialization vector (IV) to the respective cipher function. The
    IV must be unique and must be the same when
    decrypting/encrypting. With data which is stored encrypted, you
    can take the output of a function of the index under which the
    data is stored (e.g.  the MD5 key of the filename).
    Alternatively, you can transmit the IV together with the encrypted
    data (see chapter 9.3 of &book.applied.cryptography; for a
    discussion of this topic).
   </para>
  </partintro>
  
  <refentry id="function.mcrypt-get-cipher-name">
   <refnamediv>
    <refname>mcrypt_get_cipher_name</refname>
    <refpurpose>Get the name of the specified cipher</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_get_cipher_name</function></funcdef>
      <paramdef>int <parameter>cipher</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_get_cipher_name</function></funcdef>
      <paramdef>string <parameter>cipher</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     <function>Mcrypt_get_cipher_name</function> is used to get the
     name of the specified cipher.
    </para>
    <para>
     <function>Mcrypt_get_cipher_name</function> takes the cipher
     number as an argument (libmcrypt 2.2.x) or takes the cipher name
     as an argument (libmcrypt 2.4.x) and returns the name of the cipher
     or false, if the cipher does not exist.
    </para>
    <para>
     <example>
      <title><function>Mcrypt_get_cipher_name</function> Example</title>
      <programlisting role="php">
&lt;?php
$cipher = MCRYPT_TripleDES;

print mcrypt_get_cipher_name ($cipher);
?&gt;
      </programlisting>
     </example>
    </para>
    <para>
     The above example will produce:
     <programlisting>
TripleDES
     </programlisting>
    </para>
   </refsect1>
  </refentry>
  
  <refentry id="function.mcrypt-get-block-size">
   <refnamediv>
    <refname>mcrypt_get_block_size</refname>
    <refpurpose>Get the block size of the specified cipher</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_get_block_size</function></funcdef>
      <paramdef>int <parameter>cipher</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     <function>Mcrypt_get_block_size</function> is used to get the
     size of a block of the specified <parameter>cipher</parameter>.
    </para>
    <para>
     <function>Mcrypt_get_block_size</function> takes one argument, the
     <parameter>cipher</parameter> and returns the size in bytes.
    </para> 
    <para>
     See also: <function>mcrypt_get_key_size</function>.
    </para>
   </refsect1>
  </refentry>
  
  <refentry id="function.mcrypt-get-key-size">
   <refnamediv>
    <refname>mcrypt_get_key_size</refname>
    <refpurpose>Get the key size of the specified cipher</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_get_key_size</function></funcdef>
      <paramdef>int <parameter>cipher</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     <function>Mcrypt_get_key_size</function> is used to get the size
     of a key of the specified <parameter>cipher</parameter>.
    </para>
    <para>
     <function>mcrypt_get_key_size</function> takes one argument, the
     <parameter>cipher</parameter> and returns the size in bytes.
    </para> 
    <para>
     See also: <function>mcrypt_get_block_size</function>.
    </para>
   </refsect1>
  </refentry>
  
  <refentry id="function.mcrypt-create-iv">
   <refnamediv>
    <refname>mcrypt_create_iv</refname>
    <refpurpose>
     Create an initialization vector (IV) from a random source
    </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string
      <function>mcrypt_create_iv</function></funcdef>
      <paramdef>int <parameter>size</parameter></paramdef>
      <paramdef>int <parameter>source</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     <function>Mcrypt_create_iv</function> is used to create an IV.
    </para>
    <para>
     <function>mcrypt_create_iv</function> takes two arguments,
     <parameter>size</parameter> determines the size of the IV,
     <parameter>source</parameter> specifies the source of the IV.
    </para>
    <para>
     The source can be MCRYPT_RAND (system random number generator),
     MCRYPT_DEV_RANDOM (read data from /dev/random) and
     MCRYPT_DEV_URANDOM (read data from /dev/urandom). If you use
     MCRYPT_RAND, make sure to call srand() before to initialize the
     random number generator.
    </para>
    <para>
     <example>
      <title><function>Mcrypt_create_iv</function> example</title>
      <programlisting role="php">
&lt;?php
$cipher = MCRYPT_TripleDES;
$block_size = mcrypt_get_block_size ($cipher);
$iv = mcrypt_create_iv ($block_size, MCRYPT_DEV_RANDOM);
?&gt;
      </programlisting>
     </example>
    </para>
   </refsect1>
  </refentry>
 
  <refentry id="function.mcrypt-cbc">
   <refnamediv>
    <refname>mcrypt_cbc</refname>
    <refpurpose>Encrypt/decrypt data in CBC mode</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_cbc</function></funcdef>
      <paramdef>int <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
      <paramdef>int <parameter>mode</parameter></paramdef>
      <paramdef>string 
       <parameter><optional>iv</optional></parameter>
      </paramdef>
     </funcprototype>
    </funcsynopsis>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_cbc</function></funcdef>
      <paramdef>string <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
      <paramdef>int <parameter>mode</parameter></paramdef>
      <paramdef>string 
       <parameter><optional>iv</optional></parameter>
      </paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     The first prototype is when linked against libmcrypt 2.2.x, the
     second when linked against libmcrypt 2.4.x.
    </para>
    <para>
     <function>Mcrypt_cbc</function> encrypts or decrypts (depending
     on <parameter>mode</parameter>) the <parameter>data</parameter>
     with <parameter>cipher</parameter> and <parameter>key</parameter>
     in CBC cipher mode and returns the resulting string.
    </para>
    <para>
     <parameter>Cipher</parameter> is one of the MCRYPT_ciphername
     constants.
    </para>
    <para>
     <parameter>Key</parameter> is the key supplied to the
     algorithm. It must be kept secret.
    </para>
    <para>
     <parameter>Data</parameter> is the data which shall be
     encrypted/decrypted.
    </para>
    <para>
     <parameter>Mode</parameter> is MCRYPT_ENCRYPT or MCRYPT_DECRYPT.
    </para>
    <para>
     <parameter>IV</parameter> is the optional initialization vector.
    </para>
    <para>
     See also: <function>mcrypt_cfb</function>,
     <function>mcrypt_ecb</function>, and
     <function>mcrypt_ofb</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-cfb">
   <refnamediv>
    <refname>mcrypt_cfb</refname>
    <refpurpose>Encrypt/decrypt data in CFB mode</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_cfb</function></funcdef>
      <paramdef>int <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
      <paramdef>int <parameter>mode</parameter></paramdef>
      <paramdef>string <parameter>iv</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_cfb</function></funcdef>
      <paramdef>string <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
      <paramdef>int <parameter>mode</parameter></paramdef>
      <paramdef>string 
       <parameter><optional>iv</optional></parameter>
      </paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     The first prototype is when linked against libmcrypt 2.2.x, the
     second when linked against libmcrypt 2.4.x.
    </para>
    <para>
     <function>Mcrypt_cfb</function> encrypts or decrypts (depending
     on <parameter>mode</parameter>) the <parameter>data</parameter>
     with <parameter>cipher</parameter> and <parameter>key</parameter>
     in CFB cipher mode and returns the resulting string.
    </para>
    <para>
     <parameter>Cipher</parameter> is one of the MCRYPT_ciphername
     constants.
    </para>
    <para>
     <parameter>Key</parameter> is the key supplied to the
     algorithm. It must be kept secret.
    </para>
    <para>
     <parameter>Data</parameter> is the data which shall be
     encrypted/decrypted.
    </para> 
    <para>
     <parameter>Mode</parameter> is MCRYPT_ENCRYPT or MCRYPT_DECRYPT.
    </para>
    <para>
     <parameter>IV</parameter> is the initialization vector.
    </para>
    <para>
     See also: <function>mcrypt_cbc</function>,
     <function>mcrypt_ecb</function>, and
     <function>mcrypt_ofb</function>.
    </para>
   </refsect1>
  </refentry>
  
  <refentry id="function.mcrypt-ecb">
   <refnamediv>
    <refname>mcrypt_ecb</refname>
    <refpurpose>Encrypt/decrypt data in ECB mode</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_ecb</function></funcdef>
      <paramdef>int <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
      <paramdef>int <parameter>mode</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_ecb</function></funcdef>
      <paramdef>string <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
      <paramdef>int <parameter>mode</parameter></paramdef>
      <paramdef>string 
       <parameter><optional>iv</optional></parameter>
      </paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     The first prototype is when linked against libmcrypt 2.2.x, the
     second when linked against libmcrypt 2.4.x.
    </para>
    <para>
     <function>Mcrypt_ecb</function> encrypts or decrypts (depending
     on <parameter>mode</parameter>) the <parameter>data</parameter>
     with <parameter>cipher</parameter> and <parameter>key</parameter>
     in ECB cipher mode and returns the resulting string.
    </para>
    <para>
     <parameter>Cipher</parameter> is one of the MCRYPT_ciphername
     constants.
    </para>
    <para>
     <parameter>Key</parameter> is the key supplied to the
     algorithm. It must be kept secret.
    </para>
    <para>
     <parameter>Data</parameter> is the data which shall be
     encrypted/decrypted.
    </para>
    <para>
     <parameter>Mode</parameter> is MCRYPT_ENCRYPT or MCRYPT_DECRYPT.
    </para>
    <para>
     See also: <function>mcrypt_cbc</function>,
     <function>mcrypt_cfb</function>, and
     <function>mcrypt_ofb</function>.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-ofb">
   <refnamediv>
    <refname>mcrypt_ofb</refname>
    <refpurpose>Encrypt/decrypt data in OFB mode</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_ofb</function></funcdef>
      <paramdef>int <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
      <paramdef>int <parameter>mode</parameter></paramdef>
      <paramdef>string <parameter>iv</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>	
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_ofb</function></funcdef>
      <paramdef>string <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
      <paramdef>int <parameter>mode</parameter></paramdef>
      <paramdef>string 
       <parameter><optional>iv</optional></parameter>
      </paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     The first prototype is when linked against libmcrypt 2.2.x, the
     second when linked against libmcrypt 2.4.x.
    </para>
    <para>
     <function>Mcrypt_ofb</function> encrypts or decrypts (depending
     on <parameter>mode</parameter>) the <parameter>data</parameter>
     with <parameter>cipher</parameter> and <parameter>key</parameter>
     in OFB cipher mode and returns the resulting string.
    </para>    
    <para>
     <parameter>Cipher</parameter> is one of the MCRYPT_ciphername
     constants.
    </para>
    <para>
     <parameter>Key</parameter> is the key supplied to the
     algorithm. It must be kept secret.
    </para>
    <para>
     <parameter>Data</parameter> is the data which shall be
     encrypted/decrypted.
    </para> 
    <para>
     <parameter>Mode</parameter> is MCRYPT_ENCRYPT or MCRYPT_DECRYPT.
    </para>
    <para>
     <parameter>IV</parameter> is the initialization vector.
    </para>
    <para>
     See also: <function>mcrypt_cbc</function>,
     <function>mcrypt_cfb</function>, and
     <function>mcrypt_ecb</function>.
    </para>
   </refsect1>
  </refentry>
  
  <refentry id="function.mcrypt-list-algorithms">
   <refnamediv>
    <refname>mcrypt_list_algorithms</refname>
    <refpurpose>Get an array of all supported ciphers</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>array <function>mcrypt_list_algorithms</function></funcdef>
      <paramdef>string
	   <parameter>
	    <optional>lib_dir</optional>
	   </parameter>
	  </paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     <function>Mcrypt_list_algorithms</function> is used to get an
     array of all supported algorithms in the
    </para>
    <para>
     <parameter>lib_dir</parameter>.
     <function>Mcrypt_list_algorithms</function> takes as optional
     parameter a directory which specifies the directory where all
     algorithms are located. If not specifies, the value of the
	 mcrypt.algorithms_dir php.ini directive is used.
    </para>
    <para>
     <example>
      <title><function>Mcrypt_list_algorithms</function> Example</title>
      <programlisting role="php">
&lt;?php
$algorithms = mcrypt_list_algorithms ("/usr/local/lib/libmcrypt");

foreach ($algorithms as $cipher) {
	echo $cipher."/n";
}
?&gt;
      </programlisting>
     </example>
    </para>
    <para>
     The above example will produce a list with all supported
	 algorithms in the "/usr/local/lib/libmcrypt" directory.
    </para>
   </refsect1>
  </refentry>
  
  <refentry id="function.mcrypt-list-modes">
   <refnamediv>
    <refname>mcrypt_list_modes</refname>
    <refpurpose>Get an array of all supported modes</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>array <function>mcrypt_list_modes</function></funcdef>
      <paramdef>string
	   <parameter>
	    <optional>lib_dir</optional>
	   </parameter>
	  </paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     <function>Mcrypt_list_modes</function> is used to get an
     array of all supported modes in the
     <parameter>lib_dir</parameter>.
    </para>
    <para>
     <function>Mcrypt_list_modes</function> takes as optional
     parameter a directory which specifies the directory where all
     modes are located. If not specifies, the value of the
	 mcrypt.modes_dir php.ini directive is used.
    </para>
    <para>
     <example>
      <title><function>Mcrypt_list_modes</function> Example</title>
      <programlisting role="php">
&lt;?php
$modes = mcrypt_list_modes ();

foreach ($modes as $mode) {
	echo $mode."/n";
}
?&gt;
      </programlisting>
     </example>
    </para>
    <para>
     The above example will produce a list with all supported
	 algorithms in the default mode directory. If it is not set
     with the ini directive mcrypt.modes_dir, the default directory
     of mcrypt is used (which is /usr/local/lib/libmcrypt).
    </para>
   </refsect1>
  </refentry>
  
  <refentry id="function.mcrypt-get-iv-size">
   <refnamediv>
    <refname>mcrypt_get_iv_size</refname>
    <refpurpose>Returns the size of the IV belonging to a specific cipher/mode combination</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_get_iv_size</function></funcdef>
      <paramdef>string <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>mode</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     <function>Mcrypt_get_iv_size</function> returns the size of
     the Initialisation Vector (IV). On error the function returns
     FALSE. If the IV is ignored in the specified cipher/mode
     combination zero is returned.
    </para>
    <para>
     <parameter>Cipher</parameter> is one of the MCRYPT_ciphername
     constants of the name of the algorithm as string.
    </para>
    <para>
     <parameter>Mode</parameter> is one of the MCRYPT_MODE_modename
     constants of one of "ecb", "cbc", "cfb", "ofb", "nofb" or 
     "stream".
    </para>
   </refsect1>
  </refentry>
  
  <refentry id="function.mcrypt-encrypt">
   <refnamediv>
    <refname>mcrypt_encrypt</refname>
    <refpurpose>Encrypts plaintext with given parameters</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_encrypt</function></funcdef>
      <paramdef>string <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
      <paramdef>string <parameter>mode</parameter></paramdef>
      <paramdef>string 
       <parameter>
        <optional>iv</optional>
       </parameter>
      </paramdef>
     </funcprototype>
    </funcsynopsis>
    <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 '\0'.
    </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 '\0'. 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 '\0'.
    </para>
    <para>
     <example>
      <title><function>Mcrypt_encrypt</function> Example</title>
      <programlisting role="php">
&lt;?php
$iv = mcrypt_create_iv (mcrypt_get_iv_size (MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), 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";
?&gt;
      </programlisting>
     </example>
     The above example will print out:
     <programlisting>
42
64
     </programlisting>
    </para>
   </refsect1>
  </refentry>
 
  <refentry id="function.mcrypt-decrypt">
   <refnamediv>
    <refname>mcrypt_decrypt</refname>
    <refpurpose>Decrypts crypttext with given parameters</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_decrypt</function></funcdef>
      <paramdef>string <parameter>cipher</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
      <paramdef>string <parameter>mode</parameter></paramdef>
      <paramdef>string 
       <parameter>
        <optional>iv</optional>
       </parameter>
      </paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     <function>Mcrypt_decrypt</function> decrypts the data
     and returns the unencrypted 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
     is encrypted. If it's smaller that the required keysize, it
     is padded with '\0'.
    </para>
    <para>
     <parameter>Data</parameter> is the data that will be decrypted
     with the given cipher and mode. If the size of the data is not
     n * blocksize, the data will be padded with '\0'.
    </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 '\0'.
    </para>
   </refsect1>
  </refentry>
 
  <refentry id="function.mcrypt-module-open">
   <refnamediv>
    <refname>mcrypt_module_open</refname>
    <refpurpose>This function opens the module of the algorithm and the mode to be used</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>resource <function>mcrypt_module_open</function></funcdef>
      <paramdef>string <parameter>algorithm</parameter></paramdef>
      <paramdef>string <parameter>algorithm_directory</parameter></paramdef>
      <paramdef>string <parameter>mode</parameter></paramdef>
      <paramdef>string <parameter>mode_directory</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function opens the module of the algorithm and the mode
     to be used. The name of the algorithm is specified in algorithm,
     eg "twofish" or is one of the MCRYPT_ciphername constants.
     The library is closed by calling 
     <function>mcrypt_module_close</function>, but there is no need
     to call that function if <function>mcrypt_generic_end</function>
     is called. Normally it returns an encryption descriptor, or
     FALSE on error.
    </para>
    <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 (""), 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 directory are used that are
     compiled in into libmcrypt (usally /usr/local/lib/libmcrypt).
    </para>
    <para>
     <example>
      <title><function>Mcrypt_module_open</function> Example</title>
      <programlisting role="php">
&lt;?php
$td = mcrypt_module_open (MCRYPT_DES, "", MCRYPT_MODE_ECB, "/usr/lib/mcrypt-modes");
?&gt;
      </programlisting>
     </example>
     The above example will try to open the DES cipher from the default
     directory and the EBC mode from the directory /usr/lib/mcrypt-modes.
    </para>
   </refsect1>
  </refentry>
 
  <refentry id="function.mcrypt-generic-init">
   <refnamediv>
    <refname>mcrypt_generic_init</refname>
    <refpurpose>This function initializes all buffers needed for encryption</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_generic_init</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
      <paramdef>string <parameter>key</parameter></paramdef>
      <paramdef>string <parameter>iv</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     The maximum length of the key should be the one obtained by
     calling <function>mcrypt_enc_get_key_size</function> and every
     value smaller than this is legal. The IV should normally have
     the size of the algorithms block size, but you must obtain the
     size by calling <function>mcrypt_enc_get_iv_size</function>.
     IV is ignored in ECB. IV MUST exist in CFB, CBC, STREAM, nOFB
     and OFB modes. It needs to be random and unique (but not secret).
     The same IV must be used for encryption/decryption. If you do not
     want to use it you should set it to zeros, but this is not
     recommended. The function returns (-1) on error.
    </para>
    <para>
     You need to call this function before every
     <function>mcrypt_generic</function> or
     <function>mdecrypt_generic</function>.
    </para>
   </refsect1>
  </refentry>
 
  <refentry id="function.mcrypt-generic">
   <refnamediv>
    <refname>mcrypt_generic</refname>
    <refpurpose>This function encrypts data</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_generic</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function encrypts data. The data is padded with "\0"
     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>
   </refsect1>
  </refentry>
 
  <refentry id="function.mdecrypt-generic">
   <refnamediv>
    <refname>mdecrypt_generic</refname>
    <refpurpose>This function decrypts data</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mdecrypt_generic</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
      <paramdef>string <parameter>data</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function decrypts data. Note that the length of the
     returned string can in fact be longer then the unencrypted
     string, due to the padding of the data.
    </para>
    <para>
     <example>
      <title><function>Mdecrypt_generic</function> Example</title>
      <programlisting role="php">
&lt;?php
$iv_size = mcrypt_enc_get_iv_size ($td));
$iv = @mcrypt_create_iv ($iv_size, MCRYPT_RAND);

if (@mcrypt_generic_init ($td, $key, $iv) != -1)
{
    $c_t = mcrypt_generic ($td, $plain_text);
    @mcrypt_generic_init ($td, $key, $iv);
    $p_t = mdecrypt_generic ($td, $c_t);
}
if (strncmp ($p_t, $plain_text, strlen($plain_text)) == 0)
    echo "ok";
else
    echo "error";
?&gt;
      </programlisting>
     </example>
     The above example shows how to check if the data before the
     encryption is the same as the data after the decryption.
    </para>
   </refsect1>
  </refentry>
 
  <refentry id="function.mcrypt-generic-end">
   <refnamediv>
    <refname>mcrypt_generic_end</refname>
    <refpurpose>This function terminates encryption</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>bool <function>mcrypt_generic_end</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function terminates encryption specified by the encryption
     descriptor (td). Actually it clears all buffers, and closes
     all the modules used. Returns FALSE on error, or TRUE on succes.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-enc-self-test">
   <refnamediv>
    <refname>mcrypt_enc_self_test</refname>
    <refpurpose>This function runs a self test on the opened module</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_enc_self_test</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function runs the self test on the algorithm specified by the
     descriptor td. If the self test succeeds it returns zero. In case
     of an error, it returns 1.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-enc-is-block-algorithm-mode">
   <refnamediv>
    <refname>mcrypt_enc_is_block_algorithm_mode</refname>
    <refpurpose>Checks whether the encryption of the opened mode works on blocks</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_enc_is_block_algorithm_mode</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns 1 if the mode is for use with block algorithms,
     otherwise it returns 0. (eg. 0 for stream, and 1 for cbc, cfb, ofb).
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-enc-is-block-algorithm">
   <refnamediv>
    <refname>mcrypt_enc_is_block_algorithm</refname>
    <refpurpose>Checks whether the algorithm of the opened mode is a block algorithm</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_enc_is_block_algorithm</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns 1 if the algorithm is a block algorithm,
     or 0 if it is a stream algorithm.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-enc-is-block-mode">
   <refnamediv>
    <refname>mcrypt_enc_is_block_mode</refname>
    <refpurpose>Checks whether the opened mode outputs blocks</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_enc_is_block_mode</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns 1 if the mode outputs blocks of bytes or
     0 if it outputs bytes. (eg. 1 for cbc and ecb, and 0 for cfb and
     stream).
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-enc-get-block-size">
   <refnamediv>
    <refname>mcrypt_enc_get_block_size</refname>
    <refpurpose>Returns the blocksize of the opened algorithm</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_enc_get_block_size</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns the block size of the algorithm specified by
     the encryption descriptor td in bytes.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-enc-get-key-size">
   <refnamediv>
    <refname>mcrypt_enc_get_key_size</refname>
    <refpurpose>Returns the maximum supported keysize of the opened mode</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_enc_get_key_size</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns the maximum supported key size of the
     algorithm specified by the encryption descriptor td in bytes.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-enc-get-supported-key-sizes">
   <refnamediv>
    <refname>mcrypt_enc_get_supported_key_sizes</refname>
    <refpurpose>Returns an array with the supported keysizes of the opened algorithm</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>array <function>mcrypt_enc_get_supported_key_sizes</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     Returns an array with the key sizes supported by the algorithm
     specified by the encryption descriptor. If it returns an empty
     array then all key sizes between 1 and
     <function>mcrypt_enc_get_key_size</function> are supported by the
     algorithm.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-enc-get-iv-size">
   <refnamediv>
    <refname>mcrypt_enc_get_iv_size</refname>
    <refpurpose>Returns the size of the IV of the opened algorithm</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_enc_get_iv_size</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns the size of the iv of the algorithm
     specified by the encryption descriptor in bytes. If it returns
     '0' then the IV is ignored in the algorithm. An IV is used in
     cbc, cfb and ofb modes, and in some algorithms in stream mode.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-enc-get-algorithms-name">
   <refnamediv>
    <refname>mcrypt_enc_get_algorithms_name</refname>
    <refpurpose>Returns the name of the opened algorithm</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_enc_get_algorithms_name</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns the name of the algorithm.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-enc-get-modes-name">
   <refnamediv>
    <refname>mcrypt_enc_get_modes_name</refname>
    <refpurpose>Returns the name of the opened mode</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>string <function>mcrypt_enc_get_modes_name</function></funcdef>
      <paramdef>resource <parameter>td</parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns the name of the mode.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-module-self-test">
   <refnamediv>
    <refname>mcrypt_module_self_test</refname>
    <refpurpose>This function runs a self test on the specified module</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>bool <function>mcrypt_module_self_test</function></funcdef>
      <paramdef>string <parameter>algorithm</parameter></paramdef>
      <paramdef>string <parameter><optional>lib_dir</optional></parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function runs the self test on the algorithm specified.
     The optional <parameter>lib_dir</parameter> parameter can contain
     the location of where the algorithm module is on the system.
    </para>
    <para>
     The function returns TRUE if the self test succeeds, or FALSE when
     if fails.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-module-is-block-algorithm-mode">
   <refnamediv>
    <refname>mcrypt_module_is_block_algorithm_mode</refname>
    <refpurpose>This function returns if the the specified module is a block algorithm or not</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>bool <function>mcrypt_module_is_block_algorithm_mode</function></funcdef>
      <paramdef>string <parameter>mode</parameter></paramdef>
      <paramdef>string <parameter><optional>lib_dir</optional></parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns TRUE if the mode is for use with block algorithms,
     otherwise it returns 0. (eg. 0 for stream, and 1 for cbc, cfb, ofb).
     The optional <parameter>lib_dir</parameter> parameter can contain
     the location where the mode module is on the system.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-module-is-block-algorithm">
   <refnamediv>
    <refname>mcrypt_module_is_block_algorithm</refname>
    <refpurpose>This function checks whether the specified algorithm is a block algorithm</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>bool <function>mcrypt_module_is_block_algorithm</function></funcdef>
      <paramdef>string <parameter>algorithm</parameter></paramdef>
      <paramdef>string <parameter><optional>lib_dir</optional></parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns TRUE if the specified algorithm is a block
     algorithm, or FALSE is it is a stream algorithm.
     The optional <parameter>lib_dir</parameter> parameter can contain
     the location where the algorithm module is on the system.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-module-is-block-mode">
   <refnamediv>
    <refname>mcrypt_module_is_block_mode</refname>
    <refpurpose>This function returns if the the specified mode outputs blocks or not</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>bool <function>mcrypt_module_is_block_mode</function></funcdef>
      <paramdef>string <parameter>mode</parameter></paramdef>
      <paramdef>string <parameter><optional>lib_dir</optional></parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns TRUE if the mode outputs blocks of bytes or
     FALSE if it outputs just bytes. (eg. 1 for cbc and ecb, and 0 for cfb
     and stream). The optional <parameter>lib_dir</parameter> parameter
     can contain the location where the mode module is on the system.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-module-get-algo-block-size">
   <refnamediv>
    <refname>mcrypt_module_get_algo_block_size</refname>
    <refpurpose>Returns the blocksize of the specified algorithm</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_module_get_algo_block_size</function></funcdef>
      <paramdef>string <parameter>algorithm</parameter></paramdef>
      <paramdef>string <parameter><optional>lib_dir</optional></parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns the block size of the algorithm specified in
     bytes. The optional <parameter>lib_dir</parameter> parameter
     can contain the location where the mode module is on the system.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-module-get-algo-key-size">
   <refnamediv>
    <refname>mcrypt_module_get_algo_key_size</refname>
    <refpurpose>Returns the maximum supported keysize of the opened mode</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>int <function>mcrypt_module_get_algo_key_size</function></funcdef>
      <paramdef>string <parameter>algorithm</parameter></paramdef>
      <paramdef>string <parameter><optional>lib_dir</optional></parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     This function returns the maximum supported key size of the
     algorithm specified in bytes. The optional
     <parameter>lib_dir</parameter> parameter can contain the
     location where the mode module is on the system.
    </para>
   </refsect1>
  </refentry>

  <refentry id="function.mcrypt-module-get-algo-supported-key-sizes">
   <refnamediv>
    <refname>mcrypt_module_get_algo_supported_key_sizes</refname>
    <refpurpose>Returns an array with the supported keysizes of the opened algorithm</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
    <funcsynopsis>
     <funcprototype>
      <funcdef>array <function>mcrypt_module_enc_get_algo_supported_key_sizes</function></funcdef>
      <paramdef>string <parameter>algorithm</parameter></paramdef>
      <paramdef>string <parameter><optional>lib_dir</optional></parameter></paramdef>
     </funcprototype>
    </funcsynopsis>
    <para>
     Returns an array with the key sizes supported by the specified
     algorithm. If it returns an empty array then all key sizes
     between 1 and <function>mcrypt_module_get_algo_key_size</function>
     are supported by the algorithm. The optional
     <parameter>lib_dir</parameter> parameter can contain the
     location where the mode module is on the system.
    </para>
   </refsect1>
  </refentry>
 
 </reference> 

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