1. School of Information Engineering, Wuhan University of Technology, Wuhan, China
2. School of Information and Electronics, Beijing Institute of Technology, Beijing, China
3. School of Computer Science and Engineering, Sun Yat-sen University, Guangzhou, China
4. Hubei Engineering Research Center on Big Data Security, School of Cyber Science and Engineering, Huazhong University of Science and Technology, Wuhan, China
5. Laboratory for Information and Decision Systems (LIDS), Massachusetts Institute of Technology, Cambridge, MA, USA