1. State Key Laboratory of Integrated Services Networks and the School of Cyber Engineering, Xidian University, Xi’an, China
2. State Key Laboratory of Integrated Service Networks, School of Cyber Engineering, Xidian University, Xi’an, China
3. Key Laboratory of Information Security of Network Systems, School of Mathematics and Computer Science, Fuzhou University, Fuzhou, China
4. School of Information Systems, Singapore Management University, 81 Victoria St, Singapore