Research On Trusted Data Access Control Method Based On Blockchai

In recent years,as privacy issues have received more and more attention,ciphertext-policy attribute-based encryption(CP-ABE)is widely used in solving user privacy protection problems.Among them,solutions based on third-party service providers are particularly popular.However,relying on third-party entities leads to trust issues and privacy risks,and the risk of cryptographic theft from a single authorized center is high.Second,most existing schemes use monotonic access structures with AND and OR gates,which use the algorithm that transforms into the access structure matrix to generate access structures that take up more space and extra time.Finally,the transparent attributes and access policies in most CP-ABE schemes seriously threaten the user’s security.Due to the transparent form of the access structure,the user’s private information may be in danger of leakage.To address the above issues,this dissertation proposes a fine-grained access control scheme combining blockchain and attribute based encryption to reach a secure and efficient access control.The main work of this dissertation is as follows:(1)To achieve secure,efficient decentralized and scalable access control,we propose a blockchain-based multi-attribute secure data access control scheme that combines blockchain with prime order attribute based encryption algorithm for optimization.We improve the scalability of blockchain,use BLS(Boneh-LynnShacham)algorithm to design multi-authorization center to avoid privacy theft and protect users’ attribute matching privacy.What’s more,we intelligently protects data privacy security of both sides of the transaction through smart contracts to achieve safe and reliable fine-grained access control.(2)To further improve the efficiency of the existing scheme,we propose an access scheme based on an improved transformation algorithm,which extends the support for access policies compared to the existing Lewko Waters method,and the generated matrix will take less space and time to produce smaller ciphertexts.In order to balance efficiency and security,we further propose the partial hidden access policy against offline dictionary attack to protects users’ policy security,and design corresponding efficient matching algorithm for hidden structure to improve efficiency under the premise of privacy protection.(3)An experimental platform is built based on blockchain and improved attribute based encryption algorithm,and a comprehensive comparison is made between the new scheme proposed in this paper and the existing classical scheme.After experimental data and theoretical analysis,it is shown that the scheme proposed in this paper can resist offline dictionary attacks while hiding attributes,is secure under the chosen plaintext attack in the random prediction model,and improves the overall algorithm performance without limiting the access policy or the size of user attribute sets while ensuring user security.Compared with the classical cloud-based attribute encryption access control scheme,this scheme improves the overall computational efficiency while ensuring security.