Research On Searchable Encryption Scheme Based On Blockchain In Cloud Environment

Cloud storage has attracted more users to outsource data to cloud servers because of its on-demand and low-cost characteristics.However,the data is beyond the user's physical control,which will lead to the problem of sensitive data leakage.To ensure the security of cloud data,the data will be encrypted before uploading.However,encrypted data will cause problems such as difficulty in searching.Therefore,keyword search on encrypted data has become an effective method.Currently,most search encryption schemes do not consider the issue of dynamic update of encrypted data,and do not detect malicious behaviors that may exist in actual situations.With the emergence of blockchain,due to its immutable and publicly verified nature,the absolute authenticity of the data stored in it is guaranteed.In order to solve the above problems,the blockchain and searchable encryption technology are combined,and the main research contents are as follows:1.In order to solve the problem of privacy leakage caused by the lack of correctness verification of search results and data update,a dynamic verifiable ciphertext retrieval scheme based on blockchain is proposed.First,the index and the AMAC are encrypted and uploaded to the blockchain,and the search results are returned to the user through the smart contract to solve the problem of incorrect results returned by the malicious cloud server.Secondly,the version pointer is introduced to point to the update state,so that the trapdoor generated by the keyword in each update state is different,so as to ensure that relevant information will not be leaked when the data is updated.And using the characteristics of Ethereum itself,the authorization information is packaged into the transaction,which realizes the authorization access control of the data owner to the user.The final security analysis shows that this scheme not only satisfies the adaptive security,but also meets the forward and backward security definitions.Experimental comparison results show that this scheme reduces index generation and verification time,and has efficient search efficiency.2.In order to solve the problem of dishonesty between users and cloud servers in a dynamic environment,a dynamic ciphertext retrieval scheme with Two-Side verification is proposed to achieve two-way verification between users and cloud servers.First,the introduction of bitmap index and homomorphic addition symmetric encryption technology,the use of bitmap index can represent all document identifiers involved in each update of a single keyword,reducing the number of cloud server searches and local index encryption times,thereby improving search and Update efficiency,and the use of homomorphic addition symmetric encryption to encrypt the bitmap index can effectively protect the safe update of data.Secondly,client upload the AMAC to the blockchain,and use the blockchain to verify the correctness of the results returned by the cloud server to prevent fraudulent behaviors between users and the cloud server.Finally,the experimental results and security analysis show that the solution meets forward and backward security,and improves efficiency in search,update,and verification.