KU Leuven: Galileo signals will become more difficult to falsify
Researchers from the Department of Electrical Engineering at KU Leuven (University of Leuven, Belgium) have designed authentication features that will make it more difficult to send out false Galileo signals.
Professor Vincent Rijmen and doctoral student Tomer Ashur from the Department of Electrical Engineering (ESAT) at KU Leuven have advised the European Commission on ways to make Galileo signals more difficult to falsify. Their authentication method involves electronic signatures, similar to methods used for online banking.
Navigation systems are based on satellites that send out signals, including their location. The distance to four or more satellites makes it possible to determine someone’s geographical position and time. But this process may go wrong when hackers send out signals of their own that drown out the real ones. As the authentic signals are blocked, the position information for the navigation system is no longer correct.
To avoid delaying the launch of Galileo, the researchers could only use the remaining “bits” in the signals for authentication purposes.
“This is why we support the TESLA method for electronic signatures,” Rijmen says.
“TESLA (Timed Efficient Stream Loss-Tolerant Authentication) signatures fit into 100 bits,” he adds. “They quickly expire, but this is not a disadvantage in the case of satellite navigation because the location is authenticated every 30 seconds or less anyway.”
The method still needs to be tested and validated before it can be made available to the general public.
“The authentication service is scheduled to become publicly available on a number of Galileo satellites in 2018,” Rijmen says. “By 2020, the method will be fully operational. To use it, however, you will need a special receiver for Galileo signals that can also verify the electronic signatures. These receivers are currently in development.”
The European Union activated its Galileo satellite navigation system in December 2016.
A system to determine the direction of arrival would be adequate to detect all of the current forms of spoofing, because the position of the satellites is adequately known for that purpose. But it would be a fair bit more complex because of needing to determine the direction of arrival of signals from several satellites. But the technology to do that is quite mature already, which should help with the development.
Of course, if the whole satellite spectrum was jammed, then an entirely different method would be required.
It’s hard to believe that modifying the navigation message will make it any harder to spoof Galileo. The raw navigation data, including the spare bits, can be streamed in real-time from any one of hundreds of reference stations worldwide, via binex/rtcm messages. By doing this, the spoofed signal would carry the exact same data as the genuine signal. How does this make it harder to falsify the Galileo signal? Especially considering that a spoofing device would probably use these reference stations to get the ephemeris anyway…