1. Key Laboratory of Cognitive Radio and Information Processing, Guilin University of Electronic Technology, Guilin, China & College of Computer, National University of Defense Technology, Changsha, China
2. College of Computer, National University of Defense Technology, Changsha, China
3. Guangxi Key Laboratory of Trusted Software, Guilin University of Electronic Technology, Guilin, China
4. Soonchunhyang University, Asan-si, Choongchungnam-do, Korea