A Blockchain-Based Privacy-Preserving Authentication Scheme for VANETs

The privacy-preserving authentication is considered as the first line of defense against the attacks in addition to preserving the identity privacy of the vehicles in the vehicular ad hoc networks (VANETs). However, the existing authentication schemes suffer from drawbacks such as nontransparency of the trusted authorities (TAs), heavy workload to revoke certificates, and high computation overhead to authenticate identities and messages. In this paper, we propose a blockchain-based privacy-preserving authentication (BPPA) scheme for VANETs. In BPPA, all the certificates and transactions are recorded permanently and immutably in the blockchain to make the activities of the semi-TAs transparent and verifiable. However, it remains a challenge how to use such blockchain effectively for authentication in real driving scenarios (e.g., high speed or large amount of messages during congestion). With a novel data structure named the Merkle Patricia tree (MPT), we extend the conventional blockchain structure to provide a distributed authentication scheme without the revocation list. To achieve conditional privacy, we allow a vehicle to use multiple certificates. The linkability between the certificates and real identity is encrypted and stored in the blockchain and can only be revealed in case of disputes. We evaluate the validity and performance of BPPA on the Hyperledger Fabric (HLF) platform for each entity. The experimental results show that the distributed authentication can be processed by individual vehicles within 1 ms, which meets the real-time requirement and is much more efficient, in terms of the processing time and storage requirement, than existing approaches.

I. Introduction

As the basic technology of the intelligent transportation systems (ITSs), the vehicular ad hoc networks (VANETs) have attracted much attention from both academia and industry. With the main goal of improving road safety and driving conditions, VANETs are established with two types of communications, namely, the vehicle-to-vehicle (V2V) communication and the vehicles-to-infrastructure (V2I) communication [1]. Through the dedicated short-range communication (DSRC), the vehicles can exchange safety messages in V2V and communicate directly with the roadside units (RSUs) in V2I [1]. Due to the open nature of VANETs, a privacy-preserving authentication scheme should be provided against potential attacks [2]. Without authentication, a malicious vehicle may impersonate any authorized vehicle to broadcast forged messages. Moreover, if the identity privacy is not preserved, the adversary can easily track the target vehicle by analyzing the broadcasted messages, which could be a serious threat to the drivers.