Deniable Searchable Symmetric Encryption

In the recent years, Searchable Symmetric Encryption (SSE) has become one of the hottest topic in cloud-computing area because of its availability and flexibility, and there are a series of SSE schemes were proposed. The adversary considered in these schemes is either honest-but-curious or malicious. However, in the real world, there also exists such adversary who has stronger power. Namely, he/she may coerce some one of the participants to disclose some communication information. The existing SSE algorithms cannot against this adversary under the premise of confidentiality. To solve this problem, in this paper we firstly introduce coercer into SSE scheme. According to the role that the coercer plays, two situations are considered. In the first situation, the adversary is an inside coercer. In the second situation, the adversary is an outside coercer. The inside coercer means the server, while the outside coercer is such person that outside of the data owner, the user and the server. In view of the ability that the coercer has, we firstly construct the deniable SSE model (i.e., Den-SSE). Then we define the property what the Den-SSE should satisfy. By using the Deniable Encryption idea, we propose a scheme that can against the outside coercer, and two scheme that can resist inside coercer. At last, we prove our schemes can meet the property that we define.