Here's a paper that proposes GPS authentication based on signing and statistics about the signals (lots of math): http://radionavlab.ae.utexas.edu/images/stori

Here's a paper that proposes GPS authentication based on signing and statistics about the signals (lots of math): http://radionavlab.ae.utexas.edu/images/stories/files/papers/nma.pdf http://radionavlab.ae.utexas.edu/images/stories/files/papers... Paper from Los Alamos with a receiver-only implementation that would use: - abnormally high signal strength - abnormally regular transmissions - a secondary time source to double-check time (e.g. NTP on a smartphone) - dead-reckoning based on accelerometers/gyroscopes/compass to double-check position http://lewisperdue.com/DieByWire/GPS-Vulnerability-LosAlamos.pdf http://lewisperdue.com/DieByWire/GPS-Vulnerability-LosAlamos...