If I'm spoofing time, I'm going to produce an entire constellation of satellites. That is, I'm going to provide a signal which looks like all of the satellites in view providing their timing signals on whatever time I want your GPS receiver to think it is. All I have to do is ensure that your receiver receives my signal loud enough that it thinks the real satellites are noise, and my signal is the real one.
This isn't that hard to accomplish, especially since there are youtube videos showing you how. On Sun, Aug 13, 2023 at 6:03 PM Jay R. Ashworth <[email protected]> wrote: > ----- Original Message ----- > > From: "Forrest Christian (List Account)" <[email protected]> > > > Let me address your points: > [ ... ] > > Let's assume you have a typical GPS-derived NTP server using a typical > > commercially available timing GNSS module. To convince that receiver > that > > it was a different time, I'd need to have an SDR that would operate in > the > > GPS band. These are widely available for under $500. You'd also need a > > laptop and a download of a GPS simulator from GitLab. With a total > > investment of $500 (assuming I already have a laptop), I now have a > system > > that can generate a GPS signal to convince your GPS receiver that it's > any > > time at all. If you're a tech neophyte, there are youtube videos on how > to > > do this. > > > > All I need to do now is add appropriate antennas and/or amplifiers to > > overcome the official GNSS signals. As you pointed out, depending on > the > > location and directivity of your antenna, this is either trivial or > becomes > > slightly more difficult. If I can see your antenna, it becomes a lot > > cheaper as I just need a relatively low-powered amplifier and a highly > > directional antenna. If I can't see your antenna, I would opt for a > > higher-power amplifier and a less directional transmit antenna to > blanket a > > wide area with the spoofed signal. > > If I'm trying to get time out of a NAVSTAR (yes, I know, shut up) receiver, > it can see like 8-20 birds, right? Is there not some voting and such > inside > such a receiver? Just letting it see one 'bird' with spoofed time doesn't > seem like it ought to work, to me; what don't I know? > > Cheers, > -- jra > -- > Jay R. Ashworth Baylink > [email protected] > Designer The Things I Think RFC > 2100 > Ashworth & Associates http://www.bcp38.info 2000 Land > Rover DII > St Petersburg FL USA BCP38: Ask For It By Name! +1 727 647 > 1274 > -- - Forrest
