Leveraging Signal Strength as a Mechanism to Secure GPS Messages

The main goal of commercial aircraft is to transport passengers for long distances in a fast and safe manner. To support this, there are many methods to ensure the correct functioning of an airplane, such as monitoring the status of each individual component, e.g., engine, flaps, no leaks in the gas tank, etc... Adversarial entities may aim to disrupt these safety measures. One of the most common attacks is the spoofing attack, which occurs when an attacker attempts to lie about their identity and pass as a trusted source. In this work, we propose three new methods of securing incoming Global Positioning System (GPS) messages based on the number of GPS antennas available. In the event of only one GPT antenna, the attacker sends messages with the same current location data as the target. Initially, the attacker sends low strength signals that keep increasing until they are stronger than the target signal. For the second method, we propose to utilize two available signals. This dual antenna approach allows not only to monitor the different signal strengths but, as a direct result of this, to determine the location the message is coming from. Using the overall direction and signal strength from the incoming messages, it is possible to track the route of the incoming message and to monitor it in search of antagonistic behavior. Lastly, the third method covers three or more available antennas. With antennas located at different places in an airport, it is possible to triangulate the location of the sender and compare it with the location received in the message. Once the location of the sender of the message is known, it can be compared with the location received in the message. This paper presents the analysis of the three proposed methods of securing GPS messages depending on the number of antennas available at an airport. In addition, this paper also reports on the analysis of GPS spoofing attack detection methods and provides recommendations that can guide the selection of the best method for securing GPS messages.