1. School of Cyber Science and Engineering, Huazhong University of Science and Technology, Wuhan, China
2. Hubei Key Laboratory of Distributed System Security, Huazhong University of Science and Technology, Wuhan, China
3. Hubei Engineering Research Center on Big Data Security, Huazhong University of Science and Technology, Wuhan, China
4. Pennsylvania State University, State College, Pennsylvania, USA