1. Institute of Cybersecurity and Cryptology, School of Computing and Information Technology, University of Wollongong, Wollongong, Australia
2. Fujian Provincial Key Laboratory of Network Security and Cryptology, School of Mathematics and Computer Science, Fujian Normal University, P. R. China
3. Center for Cyber Security, Department of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan 611731, P. R. China