protected function checkCtrl()
    {
        $requestURL = substr($this->request, 0, -38); //the last 38 characters are the CTRL param
        $hashInput = strlen($requestURL) . $requestURL;
        $this->debugMessage[] = 'REQUEST URL: ' . $requestURL;
        $this->debugMessage[] = 'GET ctrl: ' . @$this->getData['ctrl'];
        $this->debugMessage[] = 'Calculated ctrl: ' . $this->hmac($this->secretKey, $hashInput);
        if (isset($this->getData['ctrl']) && $this->getData['ctrl'] == $this->hmac($this->secretKey, $hashInput)) {
            return true;
        }
        $this->errorMessage[] = 'HASH: Calculated hash is not valid!';
        $this->errorMessage[] = 'BACKREF ERROR: ' . @$this->getData['err'];
        return false;
    }