[time-nuts] Spoofing GPS

[Jim Lux]

On 6/25/12 7:11 PM, Chris Albertson wrote:
> On Mon, Jun 25, 2012 at 6:43 PM,<lists at lazygranch.com>  wrote:
>
>> Yeah, I read it. Typical Fox. The headline isn't accurate since they
>> spoofed the civilian GPS system, not the military GPS.
>>
>
> I think it is.  Currently the military uses GPS guided drones put the
> article says they will see more and more used, even by companies like Fed
> Ex.  I don't think I deliver this will happen soon but it might.   The
> article says that these new drones will be susceptible to GPS spoofing.
>
> But there is a simple "fix" that to me seem obvious.   When you design a
> nab system for a drone they should use inertial nav.  You can't spoof an
> IMU.   But the cheap IMUs drift and need GPS updates.  So each time you
> update the INU to do a sanity check on the GPS and see if it is within the
> drift range of the IMU.  If not you assume the GPS is being spoofed and
> continue using the INU data.
>



And of course, this *is* the way almost every autopilot/nav system out 
there works..

You use IMU+GPS... GPS is long term, but crummy in the short term; IMU 
is good short term (e.g. to stabilize flight path), but crummy long term.


Not to mention that spoofing GPS is actually fairly hard to do, 
reliably.. you have to have an internally consistent set of signals and 
observables that seamlessly connects to the original natural set and 
then walks off.


jamming is easy, spoofing is hard.


I would also expect that these things will very quickly go to L1/L5 for 
"safety of life" applications, and spoofing 2 frequencies is just that 
much harder.
>