[EMAIL PROTECTED] (Ken Buchanan) on Tuesday, August 26, 2008 wrote:

>I think this is a bit different than what Michael Heyman said.  TxTag,
>IIRC, was implemented by the same company (Raytheon) that implemented
>the 407 ETR toll system in Toronto.  In the case of the 407, there is
>no image recognition done if the car has a valid transponder.  Only in
>the case of a missing or invalid transponder is the plate imagery
>used.  Supposedly the OCR has a high enough error rate that there is
>still manual verification of plates before sending a bill, and
>accordingly a $3.60 additional charge is applied per trip.
>If the images are used even when the vehicle has a valid transponder
>-- as Michael Heyman suggests is happening with E-ZPass -- then it
>might be feasible to have back end defenses against cloning, though
>not without inconvenience to customers who borrow cars, buy new cars,
>or rent cars while their own is getting serviced.  Also as Matt Blaze
>pointed out this makes the transponder wholly redundant.

I could see where knowing what the license plate should be, from
the transponder code, could feed back into the OCR and only
generate a hit when the disagreement was obvious.

In the San Francisco Bay Area, they are using the transponder codes
to measure how fast traffic is moving from place to place. They
post the times to various destinations on the electric signs when
there are no Amber alerts or other more important things to
display. It is quite convenient, and they promise they don't use it
to track people's trips.

If one were paranoid, one could put a different ID into the
transponder for each trip, and only put the one it was issued with
into it for toll crossings. :-)

Cheers - Bill

Bill Frantz        |"We used to quip that "password" is the most common
408-356-8506       | password. Now it's 'password1.' Who said users haven't
www.periwinkle.com | learned anything about security?" -- Bruce Schneier

The Cryptography Mailing List
Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]

Reply via email to