1. School of Information and Electrical Engineering; Ludong University; China
2. Fujian Provincial Key Laboratory of Network Security and Cryptology; Fujian Normal University; China
3. Department of Computer Science; City University of Hong Kong; China
4. Centre for Computer and Information Security Research, School of Computer Science and Software Engineering; University of Wollongong; Australia
5. State Key Laboratory of Integrated Service Networks (ISN); Xidian University; China
6. School of Computer Science and Technology; Shandong University; China