[Cryptography] How to crypto secure speed limit signs

Joseph Ashwood ashwood at msn.com
Wed Mar 25 18:37:55 EDT 2015

From: Natanael
Subject: Re: [Cryptography] How to crypto secure speed limit signs

> The only thing that makes sense IMHO is a good GPS and signed official map 
> data kept
> frequently updated.

That is of course the actual correct solution. The frequent updates aren't 
even a problem, an increasing number of new cars come with their own data 
connection. Today the connection is used to unlock your car via cell phone, 
there's not reason it can't be used to update not just the speed limits but 
all the road advisories in the internal database.

The cost of updating a central database is tiny. The cost of making diff 
files is tiny. The cost of distributing these diff files is small but not 
tiny, done properly even at typical cloud data costs less than $1 per year 
per vehicle, easily absorbed into the registration cost.

This gets rid of a real problem. The cost of the signs. The signs can now be 
taken down. This reduces infrastructure cost, reduces environmental impact. 
Reduces maintenance costs. Reduces visible intrusions. Eliminates sign 
theft. And of course, the signs in place can simply be left in place. This 
also works under the implied speed limits that Darren noted (they'd no 
longer be implied but explicit in the database).

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