  The US Department of Transportation (USDOT) issued a proposed rule on January
12th, 2017 to mandate vehicle-to-vehicle (V2V) safety communications in light
vehicles in the US. Cybersecurity and privacy are major challenges for such a
deployment. The authors present a Security Credential Management System (SCMS)
for vehicle-to-everything (V2X) communications in this paper, which has been
developed by the Crash Avoidance Metrics Partners LLC (CAMP) under a
Cooperative Agreement with the USDOT. This system design is currently
transitioning from research to Proof-of-Concept, and is a leading candidate to
support the establishment of a nationwide Public Key Infrastructure (PKI) for
V2X security. It issues digital certificates to participating vehicles and
infrastructure nodes for trustworthy communications among them, which is
necessary for safety and mobility applications that are based on V2X
communications. The main design goal is to provide both security and privacy to
the largest extent reasonable and possible. To achieve a reasonable level of
privacy in this context, vehicles are issued pseudonym certificates, and the
generation and provisioning of those certificates are divided among multiple
organizations. Given the large number of pseudonym certificates per vehicle,
one of the main challenges is to facilitate efficient revocation of misbehaving
or malfunctioning vehicles, while preserving privacy against attacks from
insiders. The proposed SCMS supports all identified V2X use-cases and
certificate types necessary for V2X communication security.
  This paper is based upon work supported by the USDOT. Any opinions, findings,
and conclusions or recommendations expressed in this publication are those of
the Authors ("we") and do not necessarily reflect the view of the USDOT.
