The rapid advancement of intelligent transportation systems has significantly improved vehicular networks, particularly in applications such as vehicular platoons, which enhance fuel efficiency, road capacity, and traffic safety. However, vehicular platoons require frequent cross-domain communication across different administrative jurisdictions, which poses significant challenges to cross-domain authentication and privacy preservation. Existing cross-domain authentication schemes often suffer from high computation overhead, insufficient privacy protection, and limited support for dynamic platoon membership, making them difficult to scale to large-scale and highly dynamic cross-domain vehicular platoon scenarios. To overcome these challenges, in this paper, we propose a novel privacy-preserving cross-domain authentication (PPCDA) scheme for vehicular platoons. The PPCDA scheme ensures both vehicle identity legitimacy and message integrity, while preserving privacy for vehicles. Additionally, we introduce a batch authentication mechanism to process multiple cross-domain requests from various vehicular platoons simultaneously, alongside a scalable dynamic authentication mechanism to accommodate the dynamic nature of vehicular platooning. Compared with existing cross-domain authentication schemes, the proposed PPCDA scheme achieves improved security and authentication efficiency for vehicular platoons, with average reductions of 56.4% in authentication latency and 8.8% in communication overhead, which makes it particularly suitable for large-scale and dynamic cross-domain vehicular platoon scenarios.

Vehicular platoon, a cutting-edge technology in the realm of intelligent transportation systems, holds the promise of transforming vehicle operations on roadways. By fostering seamless communication among vehicles and leveraging advanced automation, vehicular platoon enables vehicles to travel closely together, thereby reducing aerodynamic drag, optimizing fuel consumption, and improving road safety. However, due to their open and highly dynamic characteristics, the existing platoon communication schemes face efficiency and privacy challenges. These challenges stem from a substantial overhead on the Trusted Authority (TA) and vehicle sides during platoon communication, and a lack of multi-dimensional privacy preservation (e.g., identity privacy, location privacy, attribute privacy, and reputation value privacy) for platoon vehicles. To overcome these challenges, in this paper, we propose an efficient and multi-dimensional privacy-preserving platoon communication (EMPPC) scheme. Specifically, platoon formation is cloud-assisted and relies on the location, attribute, and reputation value of vehicles. We introduce a secure reputation value ciphertext comparison (SRCC) protocol during platoon leader selection, and present an attribute verification and matching (AVM) algorithm during platoon followers matching. Theoretical analysis and simulation evaluation demonstrate that the EMPPC scheme can offer multi-dimensional privacy preservation, and it is secure and efficient for platoon communication.