[Cryptography] How to crypto secure speed limit signs
Joseph Ashwood
ashwood at msn.com
Thu Mar 26 21:20:05 EDT 2015
Replying to both Jonathan and Bill in one message.
>Jonathan
> Beware the closed-world fallacy: There are a lot of existing cars
> which don't/won't grok the new high-tech signs
It would be cheaper to require those vehicles have a compatible receiver
installed. This role can be quickly covered by the smart phone. Considering
that the entire US roadway system is the world's largest, and has been
storable in flash memory for well over a decade, the costs are trivial.
Today's smart phone could store the entire Eurasia super continent and not
miss the storage space.
> And most jurisdictions like to encourage tourism, including tourists
> driving in from other countries in their own cars
That's what a border crossing is for. It isn't a massive dataset, only a few
MB. A quick data update at the border, and everything works just fine.
> [A distinct point... how do we power these high-tech signs?
By not moving to the horribly expensive high tech signs. Instead, we retire
the signs.
>Bill
>* The system will have to support old technology for a long time.
Not very long. Use the available technology. Sure that 1939 truck won't have
it, but that 2015 cellphone in the cab with you certainly has the power.
> "GPS isn't good enough to get you back to your car. It's good enough to
> get you back to the parking lot."
Differential calculations are important here. At driving speeds the
differential calculations works to identify the road itself precisely and it
is entirely possible to determine not only which lane the vehicle is in
(important due to lane restrictions for some vehicles) but even to determine
where in the vehicle the GPS receiver is located.
Just as a side note on that, Android actually has a feature that tracks
where you parked using GPS has always been accurate to within a couple of
parking spaces for me. Today even stationary GPS is bordering on being able
to get you back to your car, moving GPS with differential calculation is
good enough to get you back to the random peanut that fell under your seat 6
months ago.
>* Any solution needs to deal with the jurisdictions which use
speeding as a revenue source.
My proposal: They're screwed. Any change to the speed limit would have to be
registered, or the jurisdiction will have to answer for it in court, safe
bet that a lawyer will take this case. It is my firm opinion that such
jurisdictions should be required to find other sources of revenue, revenue
that is actually legitimate.
I am deliberately leaving alone policy decision like Bill brings up:
> * It may well be that a majority of the drivers will not support the
> system with the current speed limits.
> Being speed limited while trying to pass on a 2 lane highway sounds
> suicidal.
Answers to those are policy not technology.
Joe
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