protected function _createSalt($length = 32)
    {
        static $chars ='qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM01234567890';

        $max  = strlen($chars) - 1;
        $salt = '';

        for ($i = 0; $i < $length; ++$i) {
            $salt .= $chars[(mt_rand(0, $max))];
        }

        return $salt;
    }