FasTrak is a passive system relative to the transponder -- it uses the
transponder ID, a vehicle sensor, and an axle counter to generate toll
records. The associated license plate capture-and-decode feature is only
invoked if a non-transponder-equipped or invalidated-transponder-equipped
vehicle attempts to use a transponder-controlled lane or toll booth. Its
primary purpose is to provide sufficient information for a CHP officer to
stop the offending vehicle. The original FasTrak design couldn't handle an
invalidated transponder: it assumed that all correctly-formatted responses
were from valid devices.

Most of the automated toll systems were designed in an era of expensive
processing and centralized databases: if the toll collection point can
generate a formatted record that can be subsequently processed for billing
purposes, that was sufficient functionality.

Social engineering of automated toll systems may have already arrived: as
long as the dollar amounts of the abuse lie within the noise factor of the
victim's bill (e.g., a limousine service or a trucking company) the issue of
retrofitting encryption to provide 'sufficient protection' will not be
raised.

Elliott

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