[Cryptography] How to crypto secure speed limit signs

[Jonathan Thornburg]

On Wed, Mar 25, 2015 at 03:37:55PM -0700, Joseph Ashwood wrote:
[[what to do with existing "low-tech" signs]]
> This gets rid of a real problem. The cost of the signs. The signs
> can now be taken down. [[...]]

Beware the closed-world fallacy:  There are a lot of existing cars
which don't/won't grok the new high-tech signs, so we need to keep
all the old Mk-1-eyeball signs (and keep them up-to-date, and keep
them legally binding) for plural decades until all the existing stock
of cars age out of the fleet.

And most jurisdictions like to encourage tourism, including tourists
driving in from other countries in their own cars, so we actually need
to keep all the old Mk-1-eyeball signs (and keep them up-to-date and
keep them legally binding) until all nearby countries' old cars age out
of their fleets, too.


[A distinct point... how do we power these high-tech signs?  There
are lots of roads in rural reas with no nearby power lines.  Ok, solar
cells..... until they're covered by a heavy snowfall.  Or until we
have to deal with roads in the arctic where there can be months without
sunlight.  It's probably easier to just keep the old Mk-1-eyeball signs
forever in such areas.  Which means that even new cars/laws have to be
able to deal with this "forever" in fallback mode.]

-- 
-- "Jonathan Thornburg [remove -animal to reply]" <jthorn at astro.indiana-zebra.edu>
   Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
   "There was of course no way of knowing whether you were being watched
    at any given moment.  How often, or on what system, the Thought Police
    plugged in on any individual wire was guesswork.  It was even conceivable
    that they watched everybody all the time."  -- George Orwell, "1984"