On Mon, 14 Aug 2017 12:09:43 -0400 Tim Shoppa <tsho...@gmail.com> wrote:
> I think if you are only trying to spoof a single receiver it would be > possible to walk a spoofed time/space code in a way that time moved without > so obvious of a discontinuity. I'm sure there would be effects a time-nut > could notice still. Not really. Unless you have a multi-antenna setup (see jim's email), you have nothing to compare the signal to. Even an ideal reference clock in your GPS receiver does not help, as the attacker could be tracking you in such a way that you will never see a discontinuity in time or position and that all the other sanity checks you do still don't show anything. With a two antenna setup, you can already check whether the phases add up to what you expect them to be, given your position relative to the satellites position. You do not need 3 antennas as a potential attacker can spoof the phase of some satellites correctly, but not of all at the same time. This at least gives you a spoof/no-spoof signal. With an antenna array you can do some masking of spoofers (ie placing a null where the spoofer comes from). But this increases the cost and complexity of the system super-linear with the number of antennas. Maybe one way to do it, would be to use a single receiver with a stable reference clock and switch between antennas in short succession. Ie similar to how the early single channel GPS receivers worked, but for antennas instead of SVs. But I have no idea how easy/difficult this would be to do and how well it would work against spoofers. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.