1. School of Cyberspace Security, Beijing University of Posts and Telecommunications, Beijing, China
2. Andrew and Erna Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA
3. Technology R&D Center, Beijing Goodwill Information Technology Ltd., Beijing, China
4. School of Mathematics and Statistics, Shaanxi Normal University, Xi’an, China
5. School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China