Research And Implementation Of Electronic Certificate Storage Scheme Based On Blockchain And Broadcast Proxy Re-encryption

With the advancement of digitalization and informatization,electronic evidence has become one of the common forms of evidence in judicial practice,and plays a key role in the factual adjudication of criminal,civil and administrative litigation activities.However,most of the traditional electronic evidence storage methods are centralized.The electronic evidence in the central server is vulnerable to internal attacks and tampering,resulting in a decrease in the credibility of the evidence,which will directly affect the judicial justice and credibility.Blockchain has the characteristics of decentralization,non-tampering,transparency and openness,which can effectively ensure the high consistency and security of internal data.Its technical characteristics are very in line with the needs of electronic certificates.Therefore,the electronic certificate storage system based on blockchain technology is expected to replace some functions of the notary office,and improve the efficiency of notarization while saving manpower and material resources.Aiming at the problems of low security,high storage cost and easy loss of traditional electronic storage methods,this paper proposes an electronic storage scheme based on blockchain and broadcast proxy re-encryption(BPRE).The specific work is as follows:(1)In order to solve the two problems that key escrow and proxy re-encryption cannot achieve efficient data sharing,a broadcast proxy re-encryption scheme combined with certificateless key system is proposed.In this scheme,it is decided to deploy the key generation center(KGC)and the agent in the blockchain in the form of smart contracts to eliminate the dependence on third-party agent service providers.Based on the difficult problem assumption,the security of the scheme is proved.In order to reflect the superiority of the scheme,this scheme is compared with the proxy re-encryption scheme proposed by other scholars from two aspects of communication overhead and computational overhead.(2)Based on the technical characteristics of blockchain and Inter Planetary File System(IPFS),it is decided to use a combination of blockchain and IPFS to achieve ’chain expansion ’.Electronic evidence is stored in IPFS,and its hash is encrypted and stored in the blockchain to solve the problem that the blockchain has a slow consensus due to the excessive amount of ledger data.(3)By studying the characteristics and application scenarios of the electronic certificate storage system,the functional and non-functional requirements of the electronic certificate storage system are analyzed.Then,based on the broadcast agent re-encryption scheme designed in this dissertation,the overall system architecture is built,and each functional module is divided and designed.Finally,the electronic certificate storage scheme proposed in this paper is implemented and tested.The test results show that each functional module of the system can achieve the expected effect and meet the requirements of electronic certificate storage.