1. Department of Electronics and Information Engineering; Huazhong University of Science and Technology; Wuhan 430074 China
2. Guangxi Key Laboratory of Trusted Software, School of Mathematics and Computational Science; Guilin University of Electronic Technology; Guilin 541004 China
3. School of Computer Science; China University of Geosciences; Wuhan 430074 China
4. Department of Information Engineering and Computer Science; Feng Chia University; Taichung 40724 Taiwan
5. Department of Computer Science and Information Engineering; Asia University; Taichung 41354 Taiwan