Searchable symmetric encryption supporting update

Cloud service enables users not only to save their data to an external server but also to process the data at the server. However, the data stored at could server may be stolen and tampered with by malicious party or administrator of the server. If user encrypts data before storing his data to the server to solve this problem, the data won't be leaked to the others. However, no operation can be performed if data are encrypted. To overcome such problem, a cryptographic protocol called SSE-1 was proposed where SSE-1 allows user to search with keyword over encrypted data. However, it is difficult to put SSE-1 to practical use since SSE-1 does not support addition and deletion operations. In this paper, we propose new protocol named ASSE (Array SSE). ASSE is a protocol for searchable encryption supporting addition and deletion operations. In ASSE, index is represented by simple bit sequence whereas linked list is employed to implement index in SSE-1. We implement ASSE and run it on Tomcat server. Implementation result shows that search, deletion, and additions operation takes 4ms, 4ms, and 610ms, respectively, for the system with 10,000 keywords and 200,000 documents. The result show that the ASSE is highly practical.