Efficient Distribution of Key Chain Commitments for Broadcast Authentication in V2V Communications

Road safety applications such as intersection collision warning, emergency brake warnings, etc., rely on the periodic broadcast of messages by vehicles and roadside infrastructure. PKI-based approaches ensuring the integrity of messages and the legitimacy of the sender are computationally expensive and result in long messages. Approaches based on hashed key chains such as Timed Efficient Stream Loss-tolerant Authentication (TESLA) offer an alternative solution. Because they use symmetric-key cryptography, the messages are shorter and less expensive to verify. However, they bring their own challenges. This paper focuses on one challenge, the problem of distributing key chain commitments required for message verification. We propose and evaluate two techniques, respectively involving periodic broadcast of commitment keys by the vehicles themselves and selective unicasting by a central V2X Application Server (VAS). We find that the VAS-centric solution has advantages over the vehicle-centric solution and a related solution proposed by other researchers.