“ Verify - on - Demand ” - A Practical and Scalable Approach for Broadcast Authentication in Vehicle - to - Vehicle Communication 2011 - 01 - 0584 Published 04 / 12 / 2011

In general for Vehicle-to-Vehicle (V2V) communication, message authentication is performed on every received wireless message by conducting verification for a valid signature, and only messages that have been successfully verified are processed further. In V2V safety communication, there are a large number of vehicles and each vehicle transmits safety messages frequently; therefore the number of received messages per second would be large. Thus authentication of each and every received message, for example based on the IEEE 1609.2 standard, is computationally very expensive and can only be carried out with expensive dedicated cryptographic hardware. An interesting observation is that most of these routine safety messages do not result in driver warnings or control actions since we expect that the safety system would be designed to provide warnings or control actions only when the threat of collision is high. If the V2V system is designed to provide too frequent warnings or control actions, then the system would be a nuisance to the driver. Therefore it is reasonable to define an approach where messages are first processed and then authenticated using verification on-demand. In this paper we describe such an approach and discuss its implementation for V2V safety system. It is shown that Verify-on-Demand (VoD) is a practical and scalable approach for broadcast authentication in V2V safety communication while conforming to the IEEE 1609.2 standard. INTRODUCTION In Vehicle-to-Vehicle communication (V2V), vehicles equipped with a short range wireless transceiver and a Global Positioning System (GPS) receiver regularly exchange safetyrelated information including time, location, and further vehicle status data amongst neighboring vehicles [1]. The communication, in general, is done as a single-hop, periodic broadcast although multi-hop routing may also be used to extend the geographical range and region of message reception [2]. It is expected that periodic vehicle broadcast of safety information would be around 10 messages per second with an average message size about 200 bytes [3]. The required transmission range of safety messages is approximately 300 meters for V2V safety communication applications. It is expected that V2V would employ the wireless communication protocol based on IEEE 802.11p Dedicated Short Range Communications (DSRC) in the 5.9 GHz band [4], although other short range wireless protocols may also be used. Security is a core issue for V2V safety communication [5]. In particular, vehicles need to be able to authenticate that a received message originated from a properly certified vehicle and that the message was not manipulated on its way between the sender and receiver vehicles. It is assumed that there is a Public Key Infrastructure (PKI) deployed and the messages are authenticated using digital signatures in accordance with the IEEE 1609.2 standard specification [6]. IEEE 1609.2 describes a message format of secured safety messages in a V2V network. IEEE 1609.2 suggests an API and message format for using security features based on Elliptic Curve “Verify-on-Demand” A Practical and Scalable Approach for Broadcast Authentication in Vehicleto-Vehicle Communication 2011-01-0584 Published 04/12/2011