Study And Application Of Traceable Double-Layer Consortium Blockchain

As a kind of blockchain technology,consortium blockchain has a range of builtin features such as transparency,decentralized storage,immutability and so on.Information in many different application fields is not transparent,not public and easy to be tampered with.Consortium blockchain can solve above problems.However,blockchain technology cannot trace users' identities on the promise of their privacy in those specific environments such as dangerous goods tracing,insurance records tracing and students' grades tracing.Additionally,each node in the system is obliged to store all transaction records and consequently the storage pressure of nodes is fairly high.To solve those problems above,a traceable double-layer consortium blockchain model is proposed.The correctness and feasibility of the model have been proved by applying it to online evaluation.The main works of this thesis are as follows:(1)A traceable access mechanism of the consortium blockchain based on group signature is proposed to solve the problem that it is difficult to trace the real identities of users through transaction records because users in the blockchain use the addresses calculated by their public keys as pseudonyms to conduct transactions.Before joining consortium blockchain,group members are ought to send their real identities,public keys and addresses to group manager.The group manager can track the real identities of group members by their addresses in the transaction records while others cannot obtain the mapping between real identities of group members and their addresses,which protects the privacy of group members.(2)A double-layer structure based on the index of transaction in sub chain is proposed to solve the problem of the high storage pressure of nodes in blockchain.In this model,all nodes are divided into groups and all transaction records are written into the main chain maintained by full nodes.It is unnecessary for the index-sub-chain maintained by nodes in group to keep all the complete transaction records of the whole network but keeping the summary of the transactions generated by the group is desirable,which is able to relieve the storage pressure of nodes in the group.(3)Taking the online evaluation as an example,an online evaluation scheme based on traceable double-layer consortium blockchain is proposed to overcome that grade evaluation is not transparent and grade records are easy to be tampered with.In this scheme,the process of answering a question is regarded as a transaction so that it will be public accessible and transparent.The final scores are stored in distributed nodes and cannot be tampered with.Additionally,privacy of students is promised and score records are traceable because only appropriate teachers can get real identities by score records.It is proved in online evaluation that the proposed model can relieve the storage pressure of nodes in blockchain.