Research On Big Data Security Sharing Technology Based On Blockchain And CP-ABE

In the current era of big data,massive and diverse data information has high commercial value,which will increase the possibility of criminals stealing data information and committing crimes.Therefore,how to realize data security sharing is critical.The development of cloud computing provides storage functions for data,and users can share data through cloud servers.To discover the secure sharing of data,most adopt the attribute-based encryption algorithm based on the ciphertext policy.Users write the access policy in the ciphertext,and only users who meet the access policy can access the corresponding data.But there are three problems:Firstly,the access policy is stored in the cloud server in the form of plaintext,and malicious users can infer the privacy information related to the user through the attribute information,which leads to the exposure of user privacy.Secondly,when the user attribute is revoked,it should be set that the user cannot reaccess the previous data information.At the same time,the possibility of reaccessing the data by collusion among users to obtain the relevant attribute should be reduced.Finally,the semi-trusted cloud server data storage operation cannot ensure that the user stores the data correctly.The data requester cannot guarantee the authenticity of the returned data.In recent years,decentralized blockchain technology has provided better technical support for data storage and sharing.The openness,transparency,and immutability of blockchain technology can effectively ensure the authenticity of transaction data.In the application of alliance blockchain,nodes follow the practical byzantine fault-tolerant consensus mechanism to verify the correctness of transaction data,which can effectively solve the problem of untrustworthy data.In data sharing,simply using the blockchain to store data will result in an excessive storage burden on the blockchain system.Usually,the cloud server is used as a thirdparty data storage centre and the blockchain stores data summary information.However,the efficiency of the practical byzantine fault-tolerant algorithm is low,and it is expected that improvements can be made to improve the consensus efficiency.In response to the above problems,this thesis proposes the following solutions:(1)Aiming at the problems of high consensus delay,high communication overhead,and random selection of primary nodes in original practical byzantine fault-tolerant consensus algorithms,a grouping PBFT algorithm based on verifiable random functions is proposed.Firstly,the optimal number of groups is determined by analyzing the total number of node communication in the group consensus.The random grouping of nodes is realized by combining with the verifiable random function so that the grouping results are unpredictable.Then,credibility is introduced,and the credit value is calculated according to the node transaction completion and response delay in the consensus stage within the group.The node with high credibility value is selected as the controller node.Finally,the analysis and experiments of the scheme show that,compared with the original PBFT algorithm,the consensus delay is effectively reduced,and the system communication efficiency and throughput are improved.(2)Aiming at the problems of privacy of access policies,dynamic changes of user attributes,and untrustworthy data,combined with the above improved PBFT algorithm,a blockchain-based attribute-based encryption scheme that supports policy hiding and revocation is further proposed.Firstly,the access policy of the multi-value attribute "AND" and "OR" gate is transformed into an access tree to realize policy hiding and avoid user attribute information leakage.Secondly,the attribute group key technology is used to discover instant revocation of user attributes,and the ciphertext length is guaranteed to be constant.Then,the blockchain stores information such as data abstracts and uses an improved practical Byzantine fault-tolerant consensus algorithm to verify the correctness of transaction data by nodes efficiently.Finally,the scheme is based on the DBDH assumption,which is secure under the standard model.The project is an anti-collusion attack,which ensures the scheme has strong functionality and has good encryption and decryption computational overhead.