1. College of Mathematics and Statistics, Northwest Normal University, Lanzhou, Gansu 730070, China
2. Guangxi Key Laboratory of Cryptography and Information Security, Guilin University of Electronic Technology, Guilin, Guangxi 541004, China
3. School of Mathematics, Southwest Jiaotong University, Chengdu, Sichuan 610000, China
4. School of Computer Engineering and Science, Shanghai University, Shanghai, 200444, China