Efficient multi-keyword searchable encryption based on multi-input inner-product functional encryption

With highly development of cloud computing, data owners wish to outsource their data to clouds for computational and storage resource at a lower price. In order to protect the privacy of sensitive information, they should be encrypted before being uploaded to the cloud server. However, in this way, it is hard to find data in encrypted form according to search criticisms. To solve this problem, searchable encryption has merged. In this paper, we propose a secure and efficient searchable encryption scheme supporting multi-keyword search in 1-to-n setting. The scheme is mainly applicable to the scenes that the number of keywords is limited but the number of files is huge such as sharing a comprehensive knowledge base of a certain field. By tactfully leveraging multi-input inner-product functional encryption, the cloud server is able to complete search processes with search tokens which consist of only two items. It reduces communication and transportation overhead significantly. By using an inverted index structure and super-incremental sequence, our scheme achieves efficient multi-keyword search. In addition, our scheme avoids per-query interaction between the data owner and data users. That is to say, the data owner does not need to stay online waiting for data users to search in his archives. On the other hand, the scheme also achieves partial token privacy, index privacy and token privacy at the same time.