1. School of Cyber Science and Engineering, Sichuan University, Chengdu 610065, P. R. China
2. State Key Laboratory of Cryptology, Beijing 100878, China
3. Huaxin Consulting and Designing Institute Co. Ltd., Hangzhou 310052, P. R. China
4. Faculty of Computer Science and Information Technology, University Malaya, Kuala Lumpur 50603, Malaysia
5. School of Information Engineering, Ningxia University, Yinchuan 750021, P. R. China