1. State Key Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, Beijing, China
2. School of Cyber Science and Technology, Sun Yat-sen University, Shenzhen Campus, Shenzhen, China
3. College of Engineering and Computer Science, Australian National University, Canberra, ACT, Australia
4. Beijing Key Laboratory of Intelligent Telecommunication Software and Multimedia, School of Computer Science, Beijing University of Posts and Telecommunications, Beijing, China