Research On DAG Blockchain-based Key Technologies In Trusted Vehicular Networks

The Internet of Vehicles improves driving safety,efficiency and comfort through vehicle-to-vehicle,vehicle-to-infrastructure,and vehicle-to-cloud communication methods.The application poses a huge challenge to the data transmission of the Internet of Vehicles.More importantly,due to the openness and mobility of the Internet of Vehicles,vehicles participating in communication always lack trust with each other,and even vehicle users are reluctant to share data with the network out of privacy.In addition,the data transmission between vehicles may also be subject to malicious attacks,such as data tampering,Sybil attacks,etc.On the other hand,blockchain technology has the characteristics of decentralization,immutability and irreversibility,and can establish a secure,transparent and credible information exchange ecosystem for IoV participants.In recent years,the integration of the Internet of Vehicles and blockchain technology to establish a secure and reliable Internet of Vehicles environment has gradually become a focus of attention in academia and industry.The focus of this thesis is to explore and design an efficient blockchain network architecture that can differentiate the priorities of IoV services,and realize trusted IoV computation offloading applications.Facing the problems of frequent data transmission and rapid node movement in the Internet of Vehicles,the existing blockchain technology is limited by scalability and consensus efficiency,and it is difficult to meet the requirements of the Internet of Vehicles for high efficiency and high throughput.However,because the traditional blockchain does not distinguish between services,it cannot guarantee the diversified QoS requirements of different services in the Internet of Vehicles.In addition,due to the untrustworthy environment of the Internet of Vehicles,there may be malicious nodes and attacks in the network,and an effective message reliability evaluation mechanism is urgently needed to establish a trusted vehicle interaction environment.Therefore,in view of the above challenges of applying blockchain to the Internet of Vehicles,this thesis proposes an efficient and trusted data transmission architecture for the Internet of Vehicles based on the Directed Acyclic Graph（DAG）blockchain.A reliable consensus mechanism for prioritizing services is used to enhance the DAG blockchain to meet the service delay constraints of various QoS requirements in the Internet of Vehicles.In addition,we evaluate the reliability of data transactions in the DAG blockchain and use it to generate the real-time reputation value of the vehicle to manage and constrain the future behavior of the vehicle.Finally,according to the similarity of vehicle trajectories,vehicles with similar trajectories are selected to verify and evaluate transactions published by each other as much as possible,so as to improve consensus efficiency and evaluation accuracy.Computation offloading is an effective technical means to deal with computingintensive applications in the Internet of Vehicles.The DAG blockchain mechanism proposed in this thesis is used in computation offloading,which can realize efficient and reliable computation offloading applications of the Internet of Vehicles.However,unlike traditional IoV computation offloading,the trustworthiness of offloading is at the expense of consuming part of IoV system resources,which introduces new challenges to the allocation and management of network resources.Therefore,in view of the complexity of the resources in the vehicle computation offloading network,this thesis proposes a trusted vehicle collaborative computation offloading strategy under the DAG blockchain-based IoV architecture.Specifically,we analyze and quantify the transmission delay and calculation delay of the computation offloading in the Internet of Vehicles,and obtain the delay overhead generated by the blockchain confirmation transaction by establishing an Absorbing Markov Chain model.Then we analyze the resource conflict between the vehicle computation offloading network and blockchain resource overhead,that is,the coarse-grained computation offloading strategy can speed up the confirmation speed of offloading events in the DAG blockchain,but it will cause a large calculation and transmission delay;therefore,we based on the data segment block decision,offloading service vehicle decision,and blockchain consensus parameter decision establish a multi-constraint optimization problem with the optimization goal of minimizing the total computation offloading delay,and finally use the particle swarm algorithm to solve the optimal collaborative computation offloading scheme.