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Performance of broadcast authentication for secure V2V safety applications: A holistic view

Efficient broadcast authentication has seen a lot of work in the recent past. Most broadcast authentication protocols rely on an underlying Public Key Infrastructure (PKI) to provide a point of trust from which credentials for more efficient cryptographic mechanisms for broadcast authentication can be derived. Thus, there is a logical dependence of some cryptographic credentials (e.g., verifiers for one-time signatures) on others (e.g., certificates from the PKI). However, since V2V messages are transmitted using a random access broadcast, messages containing these credentials could be lost, thereby preventing the verification of credentials depending on the lost ones. Further, since the wireless bandwidth is precious, there have been proposals to optimize the transmission of certificates and other credentials over the air. The more infrequently these are transmitted, the more is the temporal dependence on the verification times of V2V messages. On the flip side, the more frequently these are transmitted, the more is the bandwidth overhead (i.e., greater packet size) and the more the chances of packet collisions over the air. We illustrate this dilemma by means of a case-study, and advocate a holistic approach to broadcast authentication.