| Since the 21st century,the rise of technological revolution has covered the fields of network security,data security and transportation systems.The modern transportation system is becoming increasingly intelligent benefited from the concept of smart city and the maturity of technology.Vehiclar Ad-hoc network(VANET)can achieve communication between vehicles and road infrastructure,paving the way for the next generation of intelligent transportation systems.VANET aims to improve the current situation of modern transportation system,reduce the occurrence of slow driving and traffic congestion,and improve road traffic safety.In the information age,network security is extremely important.VANET must ensure that the communication between vehicles is safe and reliable,and also protect the privacy of users,especially the location privacy.Therefore,VANET adopts a hidden communication mechanism,but attackers can easily use this communication mechanism to launch Sybil attacks.The main principle of Sybil attack is that malicious nodes forge,tamper with,or steal multiple identities,and use these false identities in the attack to spread false information to undermine the security and performance of VANET.Moreover,attackers can launch other attacks through malicious nodes.This thesis aims to study the application of blockchain technology in the VANET field,utilizing tamper resistant decentralized ledgers to protect user data while storing vehicle node reputation scores to detect malicious nodes.This ledgers ensures the security,immutability and traceability of point-to-point(P2P)networks such as VANET.The main work is as follows:(1)A decentralized user identity authentication mechanism based on blockchain is proposed for Sybil attack defense in automotive self-organizing networks.By building a Hyperledger Fabric alliance chain and using Fabric-CA to generate public and private key pairs for legitimate users,the user identity can be effectively managed.At the same time,the user identity can be stored in the hyperledger to achieve user identity chaining and prevent Sybil attackers from tampering,stealing,and forging identity identities,thereby playing a role in defending against Sybil attacks.The decentralized feature of blockchain is applied to increase the credibility between users and enhance user privacy protection.The performance of the vehicle registration module and the authentication module are tested by simulation experiments.The results show that the authentication mechanism can be applied to manage user identities in the vehiclar Ad-hoc network.This mechanism can effectively solve the problems of centralization and mutual distrust among VANET nodes.(2)A user reputation system for vehiclar Ad-hoc network based on blockchain is designed to detect malicious nodes in VANET and blacklist them.The detection process is divided into three steps.Firstly,the Regional Traffic Management(RTM)is used as the verifier to calculate the credit score of the adjacent nodes separately,which is used as the total credit score of the vehicle nodes.Secondly,to periodically calculate the reputation score of the node according to the feedback of the neighboring nodes on the authenticity and effectiveness of the vehicle node’s communication behavior.Thirdly,the reputation system dynamically updates the nodes below the threshold to the blacklist and revokes the network permissions and stops the communication function according to the reputation scores reported by the neighboring nodes.Experimental analysis shows that the proposed system is effective and scalable in terms of the actual scale of the vehicular Ad-hoc network. |
