We present AutoCore, an automated crash reporting application that
uses VANETs (Vehicular Ad hoc NETworks) to provide authenticated
digital video and telemetry data. This data is recorded by vehicles
either involved in or at the scene of a crash and can be used by
investigators to reconstruct the events that lead up to the crash.  To
secure this application, we present a security infrastructure that
extends the state of the art in VANET security. In particular, the
contributions of this infrastructure include (a) the concept of
Road-worthiness Certificates, (b) use of these certificates in a
practical scheme for the distribution of cryptographic vehicle
credentials issued by regional transportation authorities, (c) a
decentralized scheme for conditionally anonymous, inter-vehicle
communication, (d) efficient support for the roaming of vehicles
between different transportation authority jurisdictions and (e) an
evaluation of our security infrastructure using AutoCore.