1. College of Mathematics and Information Science, Hebei Normal University, Shijiazhuang, Hebei, P. R. China
2. Hebei Key Laboratory of Computational Mathematics and Applications, Hebei Normal University, Shijiazhuang, Hebei, P. R. China
3. College of Information Technology, Hebei Normal University, Shijiazhuang, Hebei, P. R. China
4. Hebei Key Laboratory of Network and Information Security, Hebei Normal University, Shijiazhuang, Hebei, P. R. China