public function scoreDifference($passwordOne = null, $passwordTwo = null)
    {
        // check input
        if (!$passwordOne) {
            throw new Doozr_Exception('Missing input parameter one: $passwordOne for calculating score!');
        } elseif (!$passwordOne) {
            throw new Doozr_Exception('Missing input parameter two: $passwordTwo for calculating score!');
        }

        /*
         * basic check - shortcut
         */
        if ($passwordOne == $passwordTwo) {
            return 0;
        }

        /*
         * get cologne phonetic - soundex() works only good on english words
         */
        pre($this->_getColognePhonetic($passwordOne));
        pre($this->_getColognePhonetic($passwordTwo));

        /*
         * calculate difference of length between the two strings
         */
        $scoreDiffLength = abs(strlen($passwordOne) - strlen($passwordTwo));

        /*
         * get ASCII score
         * using different character's
         */
        $scoreDiffAscii = abs($this->_asciiSum($passwordOne) - $this->_asciiSum($passwordTwo)) / 1000;

        pred($scoreDiffAscii);
    }