The Research And Design Of Symmetric Searchable Encryption

Along with the coming of the era of information, the amount of data is increasing exponentially, which is a challenge to the traditional way of data storage. In order to reduce the costs of the local infrastructure and data management, the data can be outsourced to the third party service providers by users. However, due to privacy issues of users' data, the data must be encrypted before outsourcing. Data encryption will destroy the original semantic relations of the plaintext, it is also a hindrance to the usage of data such as search and update. Searchable encryption allows fast retrieval on encrypted data. Similar to the traditional encryption technology, the searchable encryption can be divided into two categories: symmetric searchable encryption and asymmetric searchable encryption. The thesis mainly studies multi-user searchable encryption and multi-keyword searchable encryption scheme of symmetric searchable encryption.Firstly, based on the multi-user retrieval model, a multi-user dynamic searchable encryption scheme is proposed. In this scheme, the data which has been encrypted by data owner is stored in a remote server. Meanwhile, the data owner authorizes a group of users to access the data. During the search, legitimate users generate search tokens with the private key. As soon as the server receives the token, re-encrypts the token with assistant key and performs the search on the ciphertext. In the procedure of revocation, the scheme only needs to delete the assisitant key stored on the server. Due to that the red black tree is adopted as a basic index structure, the search time complexity is sub-linear with the number of files. In addition, only a few nodes need to be updated in the update procedure. Based on the analysis of security and infeasibility, the scheme is proved to be secure and infeasible.Secondly, multi-keyword searchable encryption is also studied. Combined with the asymmetric scalar product encryption, the author improves the existed red black tree based dynamic searchable encryption and constructs a verifiable dynamic searchable encryption with multi-keyword scheme. Compared to previous schemes, the search and update operations are more efficient. The token is non-deterministic and the verification of search results is supported. The experiment results demonstrate that the scheme is efficient and can perform search and update efficiently.At last, the accomplished work is summarized, and the further research are presented.