Trust and scalable blockchain-based message exchanging scheme on VANET

Ephemeral vehicular ad hoc networks (VANETs) are large decentralized, distributed networks that communicate by exchanging information about their surroundings to make informed, real time decisions. However, a VANET, is neither trustworthy nor scalable. Currently, centralized trusted authorities determine the trustworthiness of the vehicles in the network. This is very inefficient. This paper addresses the following question: How can we determine, without central authority, the trustworthiness of a message sent by a vehicle on a distributed, decentralized, dynamic vehicular ad hoc network? The solution is based on the blockchain. We propose a Bayesian trust inference model that considers both the trustworthiness of the message and the vehicle sending the message. The model uses real time event data reports as priors in the beta distribution computation. We also introduce dynamic metrics in our model that captures the trustworthiness of the message with respect to time and distance. To reduce message overhead and increase scalability, we partition the road network into zones. The vehicles within a zone are therefore localized. Each zone consists of road side units (RSUs). Collectively, the RSUs form a blockchain network. The vehicles upload the calculated trust values to the RSU blockchain nodes. There is no need for extra infrastructure as the existing connections between the on-board units in vehicles and RSUs can be utilized. The blockchain network is implemented on a Hyperledger framework. We perform various experiments on blockchain and VANET parameters to test the feasibility of our model using the data from Winnipeg Public Works Department, Manitoba, Canada. We show that the use of previous reports as probabilistic priors in our blockchain framework model is more resilient than other research models that focus on using historical data or estimates for their simulations.