<?php
/*
 * phpCrypto.class.php5 -> phpCrypto Class (PHP5)
 */

 /**
  * @author Brandon Strauss
  * @version 0.01
  */
     
if (realpath(__FILE__) == realpath($_SERVER['SCRIPT_FILENAME']))
{
  // tell people trying to access this file directly goodbye...
  exit('This file can not be accessed directly...');
}

class phpCrypto
{
  
  private $td;
    
  // this gets called when class is instantiated
  public function __construct($key = 'MyRandomStringThatWillAlwaysBeTheSame', $iv = false, $algorithm = 'tripledes', $mode = 'ecb')
  {  
    if(extension_loaded('mcrypt') === FALSE)
    {
      $prefix = (PHP_SHLIB_SUFFIX == 'dll') ? 'php_' : '';
      dl($prefix . 'mcrypt.' . PHP_SHLIB_SUFFIX) or die('The Mcrypt module could not be loaded.');
    }

    if($mode != 'ecb' && $iv === false)
    {
      /*
        the iv must remain the same from encryption to decryption and is usually
        passed into the encrypted string in some form, but not always.
      */
      die('In order to use encryption modes other then ecb, you must specify a unique and consistent initialization vector.');
    }

    // set mcrypt mode and cipher
    $this->td = mcrypt_module_open($algorithm, '', $mode, '') ;

    // Unix has better pseudo random number generator then mcrypt, so if it is available lets use it!
    $random_seed = strstr(PHP_OS, "WIN") ? MCRYPT_RAND : MCRYPT_DEV_URANDOM;

    // if initialization vector set in constructor use it else, generate from random seed
    $iv = ($iv === false) ? mcrypt_create_iv(mcrypt_enc_get_iv_size($this->td), $random_seed) : substr($iv, 0, mcrypt_enc_get_iv_size($this->td));

    // get the expected key size based on mode and cipher
    $expected_key_size = mcrypt_enc_get_key_size($this->td);

    // we dont need to know the real key, we just need to be able to confirm a hashed version
    $key = substr(md5($key), 0, $expected_key_size);

    // initialize mcrypt library with mode/cipher, encryption key, and random initialization vector
    mcrypt_generic_init($this->td, $key, $iv);
  }
  
  public function encrypt($plain_string)
  {    
    /*
      encrypt string using mcrypt and then encode any special characters
      and then return the encrypted string
    */
    return "###" . base64_encode(mcrypt_generic($this->td, ($plain_string . "###")));
  }
  
  public function decrypt($encrypted_string)
  { 
    /*
      remove any special characters then decrypt string using mcrypt and then trim null padding
      and then finally return the encrypted string
    */
	
	if ( preg_match("/^###/", $encrypted_string) )
	{
		$tmp = $encrypted_string;
		$tmp = preg_replace("/^###/", "", $tmp);
		$tmp = trim(mdecrypt_generic($this->td, base64_decode($tmp)));
		return preg_replace("/###$/", "", $tmp);
	}
	else
	    return $encrypted_string;
  }  
  
  // this function gets called when php garbage collection destroys the object
  public function __destruct()
  {
    // shutdown mcrypt
    mcrypt_generic_deinit($this->td);

    // close mcrypt cipher module
    mcrypt_module_close($this->td);
  }

}
?>