1. School of Computer Science, Qufu Normal University, Rizhao, China
2. Fujian Provincial Key Laboratory of Network Security and Cryptology, College of Computer and Cyber Security, Fujian Normal University, Fuzhou, China
3. School of Cyberspace Science and Technology, Beijing Institute of Technology, Beijing, China
4. Department of Information Systems and Cyber Security, University of Texas at San Antonio, San Antonio, TX, USA