Research On Searchable Encryption Scheme Based On Multi-keyword In Cloud Environment

As one of the most typical services in cloud computing,cloud storage is welcomed by a large number of enterprises and users.Cloud tenants can greatly reduce the burden of local data computing and maintenance by outsourcing data to cloud servers.However,in practical application scenarios,privacy data is removed from the physical control of users,resulting in data disclosure problem.In order to ensure the security and privacy of data,which is often stored in ciphertext,but it is difficult to retrieve encrypted data.Therefore,the efficient and selective retrieval of encrypted documents by cloud tenants has attracted great attention from both industry and academia.In dynamic and massive data environment,the existing searchable encryption schemes have some problems,such as low search efficiency,low precision,poor security and so on.Therefore,under the premise of ensuring data privacy,how to improve the accuracy and efficiency of encrypted retrieval schemes has become a key technical problem to be solved.To address the above problem,The main contributions of this thesis are as follows.1.In order to improve the efficiency and precision of ciphertext retrieval,we proposed a multi-keyword ciphertext retrieval scheme based on clustering index.Firstly,the improved Chameleon algorithm is used to cluster the file vectors during which the file vectors are dimensioned by recording the position of the key words.Secondly,a retrieval algorithm suitable for clustering index is proposed,which makes it possible to eliminate a large number of file vectors irrelevant to the query vector in the query process,and reduce unnecessary consumption.Finally,in the clustering process,Jaccard similarity coefficient is introduced to calculate the similarity between the file vectors and to set the appropriate threshold to improve the quality of the cluster.The theory analysis and experimental results show that the scheme can effectively improve the efficiency and precision of ciphertext retrieval under the premise of guaranteeing the privacy and security of data.2.In order to improve the security of the ciphertext retrieval scheme,a verifiableciphertext retrieval scheme based on inverted index is proposed.First,insert the confusion keywords when building trapdoor sagainst a malicious cloud server's keyword attack.At the same time,the data cache area is introduced,which utilize the Pailliar encryption technology to blindly calculate the search results containing the obfuscated keywords,and the ciphertext data other than the target keyword is filtered out to reduce the communication overhead.Secondly,take advantage of bilinear maps to generate tags to verify search results,and verify the scheme in terms of correctness,security and reliability.Repeated experiments on real data sets,theoretical analysis and experimental results show that the proposed scheme can improve the security of ciphertext retrieval compared with the existing ciphertext retrieval schemes while ensuring retrieval efficiency.