Blockchain-based Privacy-preserving Data Crowdsouring Scheme

In recent years,Internet-based crowdsourcing schemes have brought social and economic benefits.More and more large companies choose web or mobile crowdsourcing as a new type of problem solving method.Most existing crowdsourcing schemes are based on thirdparty crowdsourcing platforms,and this centralized management method faces some inevitable problems,such as Do S attack,remote hijacking,Sybil attack and a single point of failure.And many existing crowdsourcing schemes also have risks of privacy leakage and data loss.In addition,the third-party platforms may conduct malicious arbitration on the crowdsourcing process,resulting in the unfair distribution of rewards.Therefore,it is particularly urgent to study decentralized crowdsourcing scheme to effectively avoid the problems caused by centralized management of crowdsourcing.Blockchain technology has become one of the feasible ways to achieve decentralized crowdsourcing.However,blockchainbased crowdsourcing schemes also face security and privacy issues that need to be resolved.Combining existing technologies and crowdsourcing scenarios,this thesis proposes a general framework of blockchain-based privacy-preserving data crowdsourcing scheme(BPCF),which aims to ensure that the crowdsourcing process is conducted in a decentralized manner and avoid the problems caused by the collusion between the requester and the workers.First,the thesis constructs the system model,adversary model the security goals of the framework.Subsequently,the thesis uses the homomorphic encryption algorithm and commitment scheme defined in the general form to describe the framework BPCF.Security analysis proves that the framework BPCF achieves the security goals of the fairness,solution privacy and data integrity.The framework BPCF is widely applicable to various crowdsourcing scenarios.In actual applications,it can combine the scene requirements to build a BPCF-based secure crowdsourcing scheme for specific application scenarios.Afterwards,based on the framework BPCF,the thesis builds a BPCF-based secure crowd-sourcing scheme(BPCV) for electronic voting scenarios.First,the thesis gives the system model,adversary model,and security goals of the scheme BPCV,mainly explaining the security threats when reusing the solutions.Subsequently,the thesis adopts the Pedersen commitment,the Paillier encryption algorithm and the CP-ABE algorithm to describe the scheme BPCV.Finally,on the basis that the scheme has been able to meet the goals of fairness,solution privacy and integrity,it is proved that the scheme BPCV has achieved the security goal of reusability.Finally,the thesis conducts the performance analysis of the scheme BPCV.The thesis analyzes the influence of different parameters on the computation overhead,and tests the communication overhead by building a private blockchain.In addition,through comparison with related works,it can be seen that the scheme BPCV has the better advantages in ensuring the fairness and reusability of the crowdsourcing process while balancing the computation overhead.