1. School of Computer Science & Technology, Xi’an University of Posts & Telecommunications, Xi’an, China
2. School of Cyber Engineering, Xidian University, Xi’an, China
3. State Key Laboratory of Integrated Services Networks and the School of Cyber Engineering, Xidian University, Xi’an, Shaanxi, China
4. Department of Information Systems and Cyber Security, The University of Texas at San Antonio, San Antonio, TX, USA
5. School of Information Systems, Singapore Management University, Bras Basah, Singapore