Proven Secure Tree-based Authenticated Key Agreement for Securing V2V and V2I Communications in VANETs

Vehicular ad hoc networks (VANETs) are vulnerable to many kinds of security attacks, so it is necessary to design an authenticated key agreement (AKA) scheme for securing communication channels in VANETs. Existing AKA schemes in VANETs focus on securing vehicle-to-vehicle (V2V) or vehicle-to-infrastructure (V2I) communication, rather than V2V and V2I simultaneously. Further, few key updating mechanisms, which are secure, practical, and lightweight, exist in current VANETs AKA schemes. In this paper, we propose a proven secure AKA scheme for securing V2V and V2I communications in VANETs, which can be divided into two parts. The first part is a three-party authentication process in which vehicles, road side unit (RSU), and trust authority (TA) authenticate each other. The second part is the key agreement process, which is used in the key generation and updating processes. For this phase, we design a tree-based key agreement algorithm that considers two scenarios, i.e., the joining of an authenticated vehicle and the leaving of the vehicle. The formal security proof and the security analysis show that our proposed scheme satisfies session key security and the necessary security requirements in VANETs, respectively. The performance analysis demonstrates that our proposed scheme has an advantage over several representative AKA schemes in VANETs.