php man page for mdecrypt_generic

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)