A Blockchain-based Risk Control Mechanism And Its Applications In Securing Ridesharing Services

The ridesharing application is one of the most considerable practice modes in the sharing economy.It allows the supply and demand of traffic resources to be precisely matched through network communication technology,and the usage time,carpooling space,and car usage rights to be multi-dimensionally shared,in order to improve the utilization rate of traffic resources,reduce travel costs,and alleviate traffic congestion and environmental pollution problems such as haze and noise.The sharing economy extends from social interactions among acquaintances to online transactions among strangers,making risk control,security and privacy preserving the core issues that limiting the development of the sharing economy.Existing centralized sharing economy platforms strengthen offline and online management of participants through real-name systems,background check,user portrait,reputation rating,and real-time monitoring,thereby defusing the security risks of transactions.However,this also causes a large amount of sensitive user data to gather to the centralized service platform,posing a threat to personal privacy and national security.To address the above challenges,this thesis first systematically analyzes the requirements for risk control of network transactions in the sharing economy,including six aspects of fairness,universality,security,efficiency,decentralization,and privacy preserving,and then target the security and privacy threats faced by shared mobility such as ridesharing.Based on above discussions,the thesis first designs a credit risk guarantee mechanism for network transactions in the sharing economy,using social networks and the principle of "trust is risk" to ensure the risk control of transactions between"strangers." The process of risk control for network transactions is proposed,including the initialization of risk guarantee,collection and matching of transaction information,locking of risk guarantee,execution of transaction transactions,settlement of transaction dispute and adjustment of risk guarantee,etc.Based on the public blockchain,the thesis specifically realizes a decentralized credit risk guarantee mechanism,the management of risk is on the chain,while the transaction itself is not on the chain,thus ensuring the security and efficiency of risk control.Then,the thesis carries out a formal analysis of the risk control mechanism.Firstly,it is theoretically proved that the consensus-based credit rating system is insecure.Then,a formal modeling of the networked credit risk guarantee mechanism designed above is conducted,and it is demonstrated using game theoretic tools that this risk guarantee mechanism,which enables personalized risk assessment of participants,is secure,i.e.,participants’ worst-case loss will not exceed their set risk budgets.Finally,the design and validation for the decentralized ridesharing application is carried out.The system model and design goals of the decentralized ridesharing application are proposed,and the risk control mechanism proposed above is used to provide personalized risk assessment to users participating in ridesharing and privacyprotected ridesharing matching based on the assessment results.A complete decentralized shared mobility application is designed based on the ridesharing matching protocol.The privacy and security properties of the application are theoretically analyzed,and the performance of the proposed shared mobility application is experimentally evaluated based on a publicly available ridesharing large-scale dataset to verify the effectiveness of the scheme.