Affiliation: | 1. School of Mathematics and Statistics, Henan University of Science and Technology, Luoyang 471003, China;2. Faculty of Mathematics and Statistics, Hubei Key Laboratory of Applied Mathematics, Hubei University, Wuhan, 430062, China;3. State Key Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, Beijing 100093, China;4. Department of Informatics, University of Bergen, Bergen N-5020, Norway |