1. College of Mathematics and Informatics, Fujian Normal University, Fuzhou, China
2. College of Mathematics and Informatics and the Fujian Provincial Key Laboratory of Network Security and Cryptology, Fujian Normal University, Fuzhou, China
3. School of Electronic and Information Engineering, Soochow University, Soochow, China
4. School of Cyberspace Security, Xi’an University of Posts and Telecommunications, Xi’an, China