Research On Searchable Encryption Schemes In Cloud Computing

Cloud computing has a fast development recently as a new promising industry.More and more individuals or enterprises are willing to store their local data to cloud server,so as to enjoy a large amount of computing resources,on demand low-cost network access and convenient data storage services.It also avoids the troubles of local data management and system maintenance.Although the cloud computing has many advantages,its security issues are always what people are worried about.To protect the data privacy,before being uploaded the outsourced data are usually encrypted first and then stored in the cloud in an encrypted form.Tailored to user's needs,Common plaintext search methods cannot be used to retrieve specific documents in the situation of data encryption.In order to solve this problem,searchable encryption emerges as the times require,which has become a hotspot in the research field of cloud security in recent years.In this thesis,we intensively study the searchable encryption technology in cloud computing and propose three different schemes:(1)A privacy-preserving searchable encryption scheme is proposed based on an inverted matrix.This thesis constructs an index structure using the inverted matrix,and uploads the encrypted index and ciphertexts to the cloud server.The proposed scheme realizes the secure search functionality by the trapdoor of queried keyword.The security proof and experimental analysis demonstrate the security of efficiency of the scheme.(2)The cloud server may have malicious behaviors,which results in the incompleteness or incorrectness of the returned ciphertexts collection.In order to deal with this problem,a verifiable searchable encryption scheme is proposed.In the scheme,we design a verifiable mechanism to prevent users from being cheated by the cloud server.At the same time,the scheme adopts an inverted index structure,which achieves the optimal search efficiency,i.e.,sub-linear search.Through the security analysis,it is proved that the scheme satisfies the adaptive semantic security and reliability.Extensive experimental results show that the search operation is efficient and the verification cost is small.(3)To improve the users' search experience,this thesis proposes a verifiable conjunctive keyword ranked search scheme,which realizes sub-linear conjunctive search,similarity ranking and results verification simultaneously.The scheme is proved to be secure under the definitions of adaptive semantic security and reliability.The performance analysis indicates that the scheme has the advantages of high search efficiency and low verification overhead.