md5 hash

function computeSign($sharedSecret) {
        if (!$this->isValid)
            throw new Exception(__METHOD__.": Message was not validated.");

        try {
            $bytesHash = sha1($this->GetSignatureBase(), true);

            // uprava pre PHP < 5.0
            if (strlen($bytesHash) != 20) {
                $bytes = "";
                for ($i = 0; $i < strlen($bytesHash); $i+=2)
                    $bytes .= chr(hexdec(substr($str, $i, 2)));
                $bytesHash = $bytes;
            }

            $des = mcrypt_module_open(MCRYPT_DES, "", MCRYPT_MODE_ECB, "");

            $iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($des), MCRYPT_RAND);
            mcrypt_generic_init($des, $sharedSecret, $iv);

            $bytesSign = mcrypt_generic($des, substr($bytesHash, 0, 8));

            mcrypt_generic_deinit($des);
            mcrypt_module_close($des);

            $sign = strtoupper(bin2hex($bytesSign));
        } catch (Exception $e) {
            return false;
        }
        return $sign;
    }

function getSignatureBase() {
        $sb = "{$this->data['mid']}{$this->data['amt']}{$this->data['curr']}{$this->data['vs']}{$this->data['cs']}{$this->data['rurl']}{$this->data['ipc']}{$this->data['name']}";
        return $sb;
    }

      $this->data['mid'] = $this->config->get('cardpay_merchant_key');
      $this->data['amt'] = $this->currency->format($order_info['total'], $order_info['currency'], 1.00000, FALSE);
      $this->data['curr'] = $this->currency->getCode();
      $this->data['vs'] = $this->session->data['order_id'];
     $this->data['rurl'] = HTTP_SERVER . 'index.php?route=checkout/success';
      $this->data['ipc'] = $this->request->server['REMOTE_ADDR'];
      $this->data['name'] = $order_info['payment_firstname'] . ' ' . $order_info['payment_lastname'];
   

    $this->data['sign'] = $sign;


    $this->data['rsms'] = $order_info['telephone'];
      $this->data['rem'] = $order_info['email'];
      $this->data['desc'] = substr($this->config->get('config_name'), 0, 100);
      $this->data['lang'] = $this->session->data['language'];
   
    $this->data['action'] = 'https://moja.tatrabanka.sk/cgi-bin/e-commerce/start/example.jsp?PT=CardPay&MID='. $this->data['mid'] . '&AMT='. $this->data['amt'] . '&CURR='. $this->data['curr'] . '&VS='. $this->data['vs'] . '&CS=0008&RURL='. $this->data['rurl'] . '&IPC='. $this->data['ipc'] . '&NAME='. $this->data['name'] . '&SIGN='. $this->data['sign'] . '&RSMS='. $this->data['rsms'] . '&REM='. $this->data['rem'] . '&DESC='. $this->data['desc'] . '&AREDIR=1&LANG='. $this->data['lang']; '';