Verifiable Searchable Encryption with Aggregate Keys for Data Sharing in Outsourcing Storage

In a secure data sharing system, the keyword search over encrypted files is a basic need of a user with appropriate privileges. Although the traditional searchable encryption technique can provide the privacy protection, two critical issues still should be considered. Firstly, a cloud server may be selfish in order to save its computing resources, and thus returns only a fragment of results to reply a search query. Secondly, since different keys are always used for different document sets, making a search query over massive sets and verifying the search results are both impractical for a user with massive keys. In this paper, we propose a scheme named "verifiable searchable encryption with aggregate keys". In the scheme, a data owner need only distribute a single aggregate key to other users to selectively share both search and verification privileges over his/her document sets. After obtaining such a key, a user can use it not only for generating a single trapdoor as a keyword search query, but for verifying whether the server just conducts a part of computing for the search request. Then, we define the requirements of the scheme and give a valid construction. Finally, our analysis and performance evaluation demonstrate that the scheme are practical and secure.