Delegatable searchable encryption with specified keywords for EHR systems

With the development of big data and cloud computing, more and more data owners store their data with encrypted form in the cloud server. To retrieve some data they are interested in, an important technology called searchable encryption can be adopted. Sometimes, the encrypted data are desired to be shared to some users by the data owners without destroying the user privacy. To address this problem, many works of delegated searchable encryption (DSE) have been studied. However, in the existing DSE schemes, the delegated users can make keyword search over the encrypted data without any restrictions. In some systems such as E-health record system in which the data are sensitive, it is desired that the delegated users can only make search with some specified keywords designated by the data owners. In this work, we present an efficient solution to this problem and give a concrete construction. Then we show that our construction is efficient and practical for real applications by experimental results.