def METHOD_NAME(self, secret_key):
    """
    Verifies the authenticity of a notification message.
    TODO: This is doing a form of authentication and
          this functionality should really be merged
          with the pluggable authentication mechanism
          at some point.
    """
    verification_input = NotificationMessage.SERVICE_NAME
    verification_input += NotificationMessage.OPERATION_NAME
    verification_input += self.timestamp
    h = hmac.new(key=secret_key, digestmod=sha)
    h.update(verification_input)
    signature_calc = base64.b64encode(h.digest())
    return self.signature == signature_calc