Noninteractive, Anonymously Authenticated, and Traceable Message Transmission for VANETs

Unlike sensor and other ad-hoc wireless networks, vehicularad-hoc networks (VANETs) are characterized by itshigh mobility which allows a very short communicationinterval among onboard units (OBUs) and between anOBU and road-side units (RSUs). This major characterizationmotivates the design of communication protocolsthat are noninteractive or at least require a very limitednumber of rounds between units. The challenging issueis that such protocols must satisfy a number of securityservices that could be complex by their nature.In secure VANETs protocols, anonymity and traceabilityare two important services, yet, achieving a satisfactorysecurity level for both of them—with acceptable complexity—is not an easy task due to the contradicting requirements: anonymous transmission must not be traceableby any individual while if a transmission is traceable,then anonymity is threatened. Existing secure VANETsprotocols for anonymous and traceable transmissions either,provide unconditional anonymity where traceabilityand revocation are impossible, or grant trust to a thirdpartynot to reveal the identity of a unit unless there is alegal reason. In this paper, we propose the first secure VANET protocolthat allows authenticated transmission among OBUsand RSUs and at the same time enjoys the following properties.(i) The transmission among OBUs and RSUs isnoninteractive (i.e., a one-move transmission without anyinteractive setup requirements). (ii) The authenticatedtransmission between any pair of units is anonymous (i.e.,no single authority knows any information about the identityof the communicating OBU). (iii) In serious roadcrimes (e.g., hit-and-run, road rage, etc.) and under courtorder, an OBU could be traced to its clear identity.We also show how our protocol could be used to setupa confidential session between any pair of units withoutrelying on extensive number of interactive rounds