Research On Trusted Data Sharing Based On Blockchain

Data storage and sharing based on cloud servers bring great convenience to us,but data security depends on cloud servers.Data on cloud servers may be maliciously tam-pered,and users do not have data sovereignty over their own identity information,access permission information and control information.As a decentralized ledger technology,blockchain has the characteristics of immutability,which can solve the problems in cen-tralized storage and authentication,and ensure the reliability of data,identity and access in data sharing.In the verifiable query,the existing work stores the data in the cloud service provider,and the verification structure exists on the blockchain to verify the integrity and correctness of the query.However,the traditional authentication data structure has high maintenance cost on the blockchain and does not support complex queries.In identity authentication,distributed digital identity is constructed based on block chain,and user identity is verified by selective disclosure,but there are still privacy problems of identity data.For access control,control policies are stored on the blockchain and access control is implemented through smart contracts,but as control policies increase,the cost of running the contracts becomes expensive.In view of the above problems in the existing trusted data sharing based on block chain,Thesis mainly completes the following tasks:1.Aiming at the problem that the third-party storage device cannot be trusted in data sharing and the integrity and correctness of returned shared data cannot be guaranteed,Thesis proposes an ADS SMM tree based on cryptographic accumulator.The SMM tree is divided into two parts:SMM_onchianon blockchain and SMM_offchainunder blockchain.The storage cost of SMM_onchainis logarithmic to the number of data records,and the storage cost of SMM_offchainchain is independent of the query dimension.Based on this structure,we design a verifiable multi-conditional Boolean query and a range query so that a sin-gle SMM tree can support any combination of dimensions.The optimization strategy of mismatch proof aggregation is also proposed to reduce the verification cost.2.In view of the problem that the users do not have their own data sovereignty and have the risk of privacy disclosure due to the centralized identity management and access control of data sharing,the data structure of digital identity and credentials meeting W3C specifications is proposed.A Solidity Event chained storage mechanism was built to manage DIDs and credentials on the blockchain,reducing the overhead of managing DIDs and credentials on the blockchain.The Solidity log merge technique is further proposed to solve the problem of long query times for chained storage mechanisms.Finally,a zero-knowledge disclosure scheme of identity credentials and access credentials is proposed to solve the problem of privacy disclosure in identity authentication and access control.To sum up,Thesis firstly proposes a verifiable Boolean query and range query scheme based on block chain,which solves the problems of untrusted third-party storage devices,limited supported query types and high maintenance cost on block chain in data sharing.Then,a digital identity management scheme based on block chain is proposed to solve the problem that users do not have data sovereignty and have privacy leakage.