1. National Engineering Laboratory for Wireless Security; Xi'an University of Posts and Telecommunications; Xi'an 710121 China
2. State Key Laboratory of Integrated Service Networks (ISN); Xidian University; Xi'an 710071 China
3. State Key Laboratory of Cryptology; P.O. Box 5159 Beijing 100878 China
4. School of Computer Science and Technology; Nanjing University of Posts and Telecommunications; Nanjing 210023 China
5. School of Computer Science; Guangzhou University; Guangzhou 510006 China
6. School of Computer and Software; Nanjing University of Information Science and Technology; Nanjing 210044 China