Encryption Class

crypt.php

<?php
/**
 * @author T. Werring <[email protected]>
 * @created 1-9-14 11:56
 */


/**
 * Class Crypt
 *
 */
class Crypt {

  /**
   * Singleton instance
   */
  private static $instance = null;


  /**
   * @var String $key key as binary string
   * @static
   * @access private
   */
  private static $key = null;
  /**
   * @var int $key_size length of binary key
   * @static
   * @access private
   */
  private static $key_size = 0;
  /**
   * @var int $iv_size length of binary key
   * @static
   * @access private
   */
  private static $iv_size = 0;

  /**
   * Crypt initializes default key and iv_size
   *
   * NOTE: ALWAYS create new 64 character hexadecimal string when reusing!
   * See self::makeKey for idea to generate string
   */
  private function __construct(){
      self::$key = pack('H*', $this->makeKey("SOME_RANDOM_STRING"));
      self::$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
  }

  /**
   * createInstance
   * @static
   * @access private
   * Singleton instantiation
   */
  private static function createInstance(){
      if(is_null(self::$instance)) self::$instance = new Crypt();
  }

  /**
   * Encrypt
   * Encrypt data in $string with RIJNDAEL 128 using $key or default key
   *
   * @param String $string the data to be encrypted
   * @param String|null $key encryption key, null for default Crypt::$key
   * @return String Encrypted data with base64 encoding
   */
  public static function encrypt($string,$key=null){
      self::createInstance();
      $iv = mcrypt_create_iv(self::$iv_size, MCRYPT_RAND);
      $key = self::$instance->makeKey($key);
      return base64_encode($iv . mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $string, MCRYPT_MODE_CBC, $iv));
  }

  /**
   * Decrypt
   * Decrypt data in $string with RIJNDAEL 128 using $key or default Crypt::$key
   * @param String $string base64 encrypted data
   * @param String|null $key encryption key, null for default key
   * @return String $key Decrypted data
   */
  public static function decrypt($string, $key=null){
      self::createInstance();
      $key = self::$instance->makeKey($key);
      $ciphertext_dec = base64_decode($string);
      $iv_dec = substr($ciphertext_dec, 0, self::$iv_size);
      $ciphertext_dec = substr($ciphertext_dec, self::$iv_size);
      return trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key,$ciphertext_dec, MCRYPT_MODE_CBC, $iv_dec));
  }

  /**
   * makeKey
   * Creates a key usuable by the RIJNDAL 128 encryption
   *
   * @access public
   * @return String key as binary string for encryption &you decryption
   */
  private function makeKey($keyword){
      if(is_null($keyword)) return self::$key;
      $md5kw = md5($keyword);
      $md5kw .=md5($md5kw);
      return pack('H*', $md5kw);
  }
}