private function _getCertificateFromCertifcatePath($certificatePath)
    {
        $this->_validateUrl($certificatePath); //ADDED EXTRA CHECK
        try {
            $cert = file_get_contents($certificatePath);
        } catch (Exception $ex) {
            throw new OffAmazonPaymentsNotifications_InvalidMessageException(
                "Error with signature validation - unable to request signing ".
                "certificate at " . $certificatePath, null, $ex
            );
        }

        if ($cert === false) {
            throw new OffAmazonPaymentsNotifications_InvalidMessageException(
                "Error with signature validation - unable to request signing ".
                "certificate at " . $certificatePath
            );
        }

        return $cert;
    }