Research On Secure Data Trading System Based On Blockchain

With the coming of the big data age,data trading plays an irreplaceable role in the using of data value.The data trading mode based on UMA protocol enables data owners to delegate authorization manager to control their data access more richly,and simplifies the data trading procedure,contributes to data fusion.However,the data trading mode based on UMA still includes the following security problems.Firstly,the authorization manager is not completely trusted.It may act as the attacker or collude with the attacker to tamper the critical data;Secondly,as user owns more data,a large number of tokens stored in the client might lead to token leakage or tampering;Finally,it has some problem when using token,such as attacker impersonating user to use token and token reply-attack.In order to solve above security problems of UMA protocol,in this thesis,a solution of secure data trading is proposed by introducing blockchain.The main contributions of the thesis are:(1)A decentralized access authorization method based on blockchain is proposed.The centralized authorization manager is transformed into four kinds of nodes based on blockchain: execution node,consensus node,ledger node and service node.decentralized access authorization mechanism is designed to perform authentication and authorization check,distributed data trading ledger based on blockchain is defined to store critical data.Trust problem of authorization manager can be solved by this means.(2)A token safety optimization method based on blockchain is proposed.In order to make the storage of token more secure,a token management mechanism of on-chain and off-chain dual storage based on blockchain is provided,the tokens are stored in the off-chain in blocks and the token block hash value is stored in the on-chain;In order to prevent the attacker impersonating user to use token,a user identity authentication method based on digit certificate is designed,verifying whether the user's digital certificate is consistent with the token owner's digital certificate;In order to prevent the attacker launch token reply-attack,a token passing method based on synchronization of random number is designed,verifying whether the calculation result of random number by sender is in accordance with the one by receiver based on same algorithm.(3)A prototype system of secure data trading based on blockchain is designed and implemented.The prototype system is tested for function ? performance and analyzed for security.The experimental results show that the secure data trading solution based on blockchain can solve the trust problem of authorization manager and ensure the security of token storage and use.