Research On Attribute-Based Encryption Systems Supporting Query Over Ciphertext

With the development of big data and the cloud computing technology,more and more users choose storing data on cloud servers,which brings much convenience to their management and usage of data,as well as the risk of data leakage.A common method to prevent data leakage is to encrypt the data before uploading it,but the traditional encryption method will destroy the availability of data,and it is difficult to realize the flexible data sharing and querying.Attributebased encryption and searchable encryption,as two encryption methods with special properties,can provide flexible access control and querying methods for encrypted data,so they have received widespread attention.Based on attribute-based encryption and searchable encryption,we propose two new searchable attribute-based encryption scheme in this thesis:(1)To realize the pattern matching query of any substring in the ciphertext of the text,we construct substring-searchable attribute-based encryption scheme.In this scheme,the data owner encrypts the data under an access structure,and only the data user who satisfies the access structure can query and decrypt it.The data user can make a substring query on the whole ciphertext without setting keywords in advance.We give the specific construction,security analysis and performance analysis of the scheme,and we also introduce the application of the scheme in the medical environment.(2)To query Boolean combinations of multiple keywords,we construct searchable attributebased encryption scheme with Boolean queries.In this scheme,the data owner encrypts the database containing several files for a certain access structure,and stores the encrypted database in the cloud server.A data user wants to query a file containing multiple keywords at the same time in the database.If his attributes can satisfy the access structure,the user can generate a corresponding search token for the search request.He submits the search token containing the search request to the cloud server,which performs the search and returns the results.We give the specific construction,security analysis and performance analysis of the scheme,and we also introduce the application of the scheme.