Design And Implementation Of A Secure Multi-party Computing System Based On Blockchain

The full use of the value of data is inseparable from data cooperation between data owners.An efficient and safe multiparty data joint computing is a key link in breaking data silos and realizing the data cooperation.This thesis studies the existing data cooperation and sharing models and methods,analyzes the problems of privacy protection and the safe execution of computation in the process of multiparty joint computing.This thesis designs and implements a secure multiparty computation system based on blockchain.The main work of this thesis consists of the following points:(1)Aiming at the fairness and security of multiparty computing,a secure multiparty computing scheme based on blockchain is designed.This solution combines the blockchain technology to increase the fairness in the multiparty computation process,and uses the smart contract as a decentralized third party.The participants jointly control the process of secure multiparty computation,avoiding the traditional solution relying only on a single participant to make decision.In order to improve the security of the system operation and reduce the possibility of multiple participants from collaborating to steal user data,the scheme designed a random selection module of the participants,through a verifiable random function combined with the credit value of the participants,from a set of participants are selected to participate in the computation,thereby reducing the risk of user data leakage.In order to improve the efficiency of participate interaction with blockchain,this scheme builds a multiparty computation side chain,and uses zero-knowledge proof technology to achieve data synchronization between the main chain and the side chain.The experiment verifies the validity of the scheme designed in this thesis.(2)On the basis of secure multiparty computation based on blockchain,a data security sharing scheme based on IPFS is proposed,which solves the problem of secure storage and sharing of user data.The data storage sharing scheme uses IPFS as the data storage layer for secure multiparty computation,and realizes the secure storage of MPC data through secret sharing algorithms and proxy re-encryption mechanisms,enabling users to safely store data in multiple nodes of IPFS,avoiding the risk of centralized servers obtaining private data of users.In the process of data access,this thesis designs a smart contract to control the access rights of user data.Only requests authorized by the user can access shared data.In order to improve the efficiency of data use while protecting privacy,a data protection strategy of proxy re-encryption mechanism is proposed to ensure that even if a malicious node obtains the content identifier,the decrypted plaintext data cannot be obtained.In order to improve the availability of shared data,this thesis designs an IPFS data backup mechanism to solve the problem of data loss caused by node withdrawal in a decentralized network.The experimental results show that the method in this thesis can realize the safe sharing of data with less time cost.(3)Designed and implemented a secure multiparty computation prototype system based on blockchain,which mainly includes computation task module,data sharing module and MPC module.The computation task module mainly completes the interaction between the user and the system,including functions such as computation task publishing,computation task query and computation task registration.The data sharing module mainly completes the computation of the participants to obtain the private data to be calculated.The MPC module performs the off-chain computation function.The experimental results show the overall feasibility of a secure multiparty computation system based on blockchain.