  Authenticated safety beacons in Vehicular Communication (VC) systems ensure
awareness among neighboring vehicles. However, the verification of beacon
signatures introduces significant processing overhead for resource-constrained
vehicular On-Board Units (OBUs). Even worse in dense neighborhood or when a
clogging Denial of Service (DoS) attack is mounted. The OBU would fail to
verify for all received (authentic or fictitious) beacons. This could
significantly delay the verifications of authentic beacons or even affect the
awareness of neighboring vehicle status. In this paper, we propose an efficient
cooperative beacon verification scheme leveraging efficient symmetric key based
authentication on top of pseudonymous authentication (based on traditional
public key cryptography), providing efficient discovery of authentic beacons
among a pool of received authentic and fictitious beacons, and can
significantly decrease waiting times of beacons in queue before their
validations. We show with simulation results that our scheme can guarantee low
waiting times for received beacons even in high neighbor density situations and
under DoS attacks, under which a traditional scheme would not be workable.
