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Anti-Spoofing

A GPS spoofing attack attempts to “deceive” a GPS receiver by broadcasting counterfeit GPS signals, structured to resemble a set of normal GPS signals, or by rebroadcasting genuine signals captured elsewhere or at a different time. These spoofed signals may be modified in such a way as to cause the receiver to estimate its position to be somewhere other than where it actually is, or to be located where it is but at a different time, as determined by the attacker.

Spoofing attacks had been predicted and discussed in the GPS community, but no known example of a malicious spoofing attack has yet been confirmed. However, some analysis suggests that the capture of a Lockheed RQ-170 drone aircraft in northeastern Iran in December 2011, was the result of such an attack.

For a number of years, Stanford has been performing research on how to make GPS and GPS receivers more robust to spoofing attacks. Current research includes the following techniques:

  • Using WAAS message authentication
  • Time of arrival techniques
  • Use of antenna to distinguish direction of arrival
  • Using and comparing encrypted PY code

The FAA has supported Stanford’s research in this area.

View Inside GNSS Article (PDF): A Multi-Antenna Defense Receiver-Autonomous GPS Spoofing Detection by Paul Montgomery (Novariant, Inc), Todd Humphreys (University of Teas at Austin), Brent Ledvina (Virginia Tech), March/April 2009.