Blockchain-based Decentralized Multi-skill Mobile Crowdsourcing Services Research

With the development of wireless networks and mobile smart devices,mobile crowdsourcing has attracted a lot of attention from academia and industry.But some mobile crowdsourcing task can be quite complex,and these complex tasks require skilled workers with specific expertise.Multi-skill Mobile Crowdsourcing(MS-MC)can address these complex mobile crowdsourcing scenarios and be more relevant to people’s daily lives.Traditional crowdsourcing processes are usually managed by centralized crowdsourcing platforms,while third-party crowdsourcing platforms face problems such as single point of failure,user privacy leakage,fairness arbitration,and service fees.The technical features such as decentralization and privacy protection provided by blockchain technology can well solve the above problems.Using decentralized blockchain technology instead of traditional centralized crowdsourcing platforms has become a new solution for crowdsourcing,but existing blockchain-based crowdsourcing works cannot support the multi-skilled mobile crowdsourcing.This thesis focuses on building a blockchain crowdsourcing system to support multi-skilled mobile crowdsourcing tasks.Two scheme for blockchain-based multiskilled mobile crowdsourcing are proposed to address the difficult problems such as high consumption of computational resources for task assignment,vague and variable quality assessment metrics,difficulties in location privacy protection and high Gas consumption costs.The main work of this thesis is as follows:(1)This thesis uses decentralized blockchain infrastructure to replace the centralized crowdsourcing platform in traditional crowdsourcing services,and constructs a decentralized blockchain-based multi-skilled mobile crowdsourcing service.In addition,a crowdsourcing task allocation algorithm suitable for blockchain computing-constrained environment is proposed to solve the multi-skilled crowdsourcing task allocation problem.To ensure the fairness of the crowdsourcing process,Scheme 1 implements a generic task quality assessment method based on the crowdsourcing approach.Finally,the feasibility of the system is analyzed from two perspectives: the latency of Ethereum transactions and the time complexity of the task allocation algorithm.(2)In this thesis,we designed a privacy-preserving blockchain-based multi-skilled mobile crowdsourcing with the goals of user privacy protection and smart contract consumption optimization.It defines the main objectives of privacy protection and proposes a zero-knowledge proof-based location privacy protection method.Then the implementation details of each process of the system are presented,mainly including: user register,task public,task request submit,task assignment,quality evaluate and task settlement.Subsequently,the privacy-preserving capability of Scheme 2 is demonstrated in great detail.Finally,the optimization of smart contract consumption is discussed.(3)Finally,this thesis experimented the above two schemes.For Scheme 1,the baseline task assignment algorithm is designed for simulating the related works,and the experiments are compared with the proposed task assignment algorithm.The Gas consumption of the main process in Scenario 1 was simulated through the Ethereum test network,and the transaction latency time was measured.For Scheme 2,the time overhead of zero-knowledge proof generation under different parameters was tested.Then the iterations of worker reputation values in the task settlement process were simulated under different scenarios to determine the appropriate parameter range.Then the iterations of worker reputation values in the task settlement process were simulated in different scenarios to determine the appropriate parameter range.Finally,the Gas cost consumption of the main process of Scheme 2 is simulated in detail and compared with related work.The results show that the scheme proposed in this thesis performs well in task assignment success rate and Gas consumption optimization.It meets the key requirements of multi-skilled mobile space crowdsourcing in blockchain environment,and has good prospects in future application environments.