mcrypt_module_open(3) [php man page]

MCRYPT_MODULE_OPEN(3)							 1						     MCRYPT_MODULE_OPEN(3)

mcrypt_module_open - Opens the module of the algorithm and the mode to be used

SYNOPSIS

       resource mcrypt_module_open (string  $algorithm, string	$algorithm_directory, string  $mode, string  $mode_directory)

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(3).

PARAMETERS

	      o $algorithm
		-One of the MCRYPT_ciphername constants, or the name of the algorithm as string.

	      o $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 php.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).

	      o $mode
		-One of the MCRYPT_MODE_modename constants, or one of the following strings: "ecb", "cbc", "cfb", "ofb", "nofb" or "stream".

	      o $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 php.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

       Example #1

	      mcrypt_module_open(3) 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.

       Example #2

	      Using mcrypt_module_open(3) 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 */
		  $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) . "
";
	      ?>

SEE ALSO

       mcrypt_module_close(3), mcrypt_generic(3), mdecrypt_generic(3), mcrypt_generic_init(3), mcrypt_generic_deinit(3).

PHP Documentation Group 												     MCRYPT_MODULE_OPEN(3)

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MDECRYPT_GENERIC(3)							 1						       MDECRYPT_GENERIC(3)

mdecrypt_generic - Decrypts data

SYNOPSIS

       string mdecrypt_generic (resource  $td, string  $data)

DESCRIPTION

	This  function	decrypts  data.  Note that the length of the returned string can in fact be longer than the unencrypted string, due to the
       padding of the data.

PARAMETERS

	      o $td
		- An encryption descriptor returned by mcrypt_module_open(3)

	      o $data
		- Encrypted data.

EXAMPLES

       Example #1

	      mdecrypt_generic(3) Example

	      <?php
		  /* Data */
		  $key = 'this is a very long key, even too long for the cipher';
		  $plain_text = 'very important data';

		  /* Open module, and create IV */
		  $td = mcrypt_module_open('des', '', 'ecb', '');
		  $key = substr($key, 0, mcrypt_enc_get_key_size($td));
		  $iv_size = mcrypt_enc_get_iv_size($td);
		  $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);

		  /* Initialize encryption handle */
		  if (mcrypt_generic_init($td, $key, $iv) != -1) {

		      /* Encrypt data */
		      $c_t = mcrypt_generic($td, $plain_text);
		      mcrypt_generic_deinit($td);

		      /* Reinitialize buffers for decryption */
		      mcrypt_generic_init($td, $key, $iv);
		      $p_t = mdecrypt_generic($td, $c_t);

		      /* Clean up */
		      mcrypt_generic_deinit($td);
		      mcrypt_module_close($td);
		  }

		  if (strncmp($p_t, $plain_text, strlen($plain_text)) == 0) {
		      echo "ok
";
		  } else {
		      echo "error
";
		  }
	      ?>

	The example above shows how to check if the data before the encryption is the same as the data after the decryption. It is very  important
       to reinitialize the encryption buffer with mcrypt_generic_init(3) before you try to decrypt the data.

	The  decryption  handle  should always be initialized with mcrypt_generic_init(3) with a key and an IV before calling this function. Where
       the encryption is done, you should free the encryption buffers by calling mcrypt_generic_deinit(3). See mcrypt_module_open(3) for an  exam-
       ple.

SEE ALSO

       mcrypt_generic(3), mcrypt_generic_init(3), mcrypt_generic_deinit(3).

PHP Documentation Group 												       MDECRYPT_GENERIC(3)

Linux and UNIX Man Pages

mcrypt_module_open(3) [php man page]

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