Research On Searchable Symmetric Encryption In Cloud Environment

With the development of the network and the advent of cloud storage,more and more users begin to outsource encrypted files to cloud servers to save resources and obtain convenient access.Searchable encryption allows a user to search the encrypted files without leaking information related to the contents of the files.As an important branch of searchable encryption,searchable symmetric encryption has broad application prospects.In this thesis,we intensively study the searchable symmetric encryption technology in cloud environment and propose two schemes as follows.In order to enable a user to access encrypted data,a privacy-preserving searchable symmetric encryption scheme is proposed in this thesis.The proposed scheme constructs an inverted index using the bit matrix.After encrypting the index,the user can access ciphertexts with the corresponding search tokens.In this scheme,the user does not need to store dictionaries,and the index reveals no information about the maximum number of keywords.The security analysis proves that the scheme is secure against adaptive chosen-keyword attacks.Finally,the performance evaluation demonstrates the feasibility of the scheme.In order to enable multiple users to access dynamic data sets,this thesis proposes a multi-user searchable encryption scheme with dynamic updates.The proposed scheme is applicable to the usage scenario where one data owner encrypts files and shares them among multiple users.The scheme uses key distribution and re-encryption to achieve multi-user access while avoiding a series of issues caused by key sharing.The scheme constructs a simple and practical index structure,namely the combination of a bit matrix and two static hash tables.With this index structure,the scheme avoids bilinear pairing operations and achieves efficient searches and updates.In addition,the scheme is proven secure under the specific security requirements.