Drivers in Arizona can now declare a simple security policy for their vehicles, in a voluntary scheme known as Watch Your Car. This involves a large decal on the side of the vehicle, indicating that it is not normally used between 1am and 5am. Therefore when police see a vehicle with such a decal on the road at that time, the police will stop and question the driver. As Bruce Schneier points out, a more accurate name for this scheme would be Please Stop My Car.
Bruce also points out some of the externalities of the scheme. It is clearly possible for people to use this scheme to waste police time, or even deliberately divert police attention from other more important matters. We may also note that for many people, the only thing that would cause them to be out of bed at all, let alone driving down the road at 4am, is some kind of emergency such as taking a sick child to hospital - and the last thing you want at such a time is a policeman stopping the car for some routine check.
There are also externalities that arise from the fact that every driver has exactly the same security policy. Presumably the car thieves in Arizona will be very busy just after 5am.
What I have advocated on this blog and elsewhere is the need for differentiated policies, preferably under user control. Suppose my car had a secure chip that recorded my usage preferences - which times of day I normally drive, and in which parts of town. Suppose the police had a device that could interrogate this chip and indicate that a given car was outside its normal operating zone. Alternatively, the satellite navigation device could be coded to send a secure message to the police under certain predefined conditions, similar to a burglar alarm.
With appropriate technology, it is theoretically possible to make such a scheme better for the driver (because more closely fitted to their own individual lifestyle), simpler for the police (because the technology hides the complexity) and more difficult for the criminal (because the outcome of a given action is harder to predict). Win-win-win.
But the main difference between this scheme and the banking schemes I have advocated earlier is the cost of enforcement - involving significant consumption of police resources, as well as complications for the driver. Even with proper differentiation, I am still not convinced about the merits of the scheme. However, I thought it worth posting here as a further example of the possibilities of differentiation.
Self-Service (October 2005)
Banking Services and User-Defined Policy 1 (January 2006)
Banking Services and User-Defined Policy 2 (January 2006)
Pay As You Drive (October 2006)