Research And Application Of Ranked Searchable Encryption

With the significant rise in the demand for infinite storage resource and high-quality retrieval service,cloud computing is deemed to be a highly remarkable technology.For privacy protection,data should be uploaded in ciphertext-form to the cloud server.Searchable encryption is a primitive in cryptography,which enables the cloud server to search on encrypted data,thereby reducing the computational and communication overhead of data users.However,the search results returned by traditional searchable encryption do not reveal any relevance to query keywords.As a special kind of searchable encryption,ranked searchable encryption provides effective solutions to the existing searchable encryption systems.It utilizes the multi-keyword search algorithms and ranked algorithms to resolve the problem of returning invalid and inaccurate search results.Currently available ranked searchable encryption schemes are easily vulnerable to both keyword guessing attacks and equivalence test attacks.The traditional one-to-one encryption mode lacks flexibility,has a single function.And these schemes are too expensive for communication and computational overhead to meet application requirements in different scenarios.In order to address these issues,the thesis proposes two ranked searchable encryption schemes.The first is Efficient Ranked Multi-keyword Retrieval with Privacy Protection for Multiple data Owners in Cloud Computing,and the second is Fine-Grained Ranked Multi-Keyword Search over Hierarchical Data for Io T-oriented Health System.For this thesis,the main contributions and innovations are described below:1)Propose a novel efficient ranked multi-keyword retrieval scheme with privacy protection for multiple data owners,which empowers the cloud server to perform multi-keyword search over the cloud data and then return the ranked relevance search results to data users without leaking any keyword and trapdoor information in the multiple data owner model.Additionally,the thesis shows through the rigorous security analysis that the scheme is secure against the attacks launched by inside attackers and outside attackers.Finally,the performance evaluation indicates that the scheme has more satisfactory features than the existing ranked multi-keyword search scheme.2)Propose a fine-grained ranked multi-Keyword search scheme over hierarchical data.In the background of Internet of Things-oriented health,data users are allowed to make queries for hierarchical data of their interest based on the specific keywords and gain the most relevant EHRs with high search accuracy without exposing the underlying data by leverageing ciphertext-policy hierarchical attribute-based encryption and ranked multi-keyword search technologies.Besides,fine-grained access privilege control over data is also supported in this scheme.The computation-intensive operations in the decryption phase are almost completed by cloud server while marginal operations are left to data users,which greatly improves the efficiency of data recovery.In the end,the scheme is selectively secure through security analysis is proved and the practicability and feasibility of the proposed scheme is also shown by performance evaluation.