1.School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China; School of Mathematics and Computer Science, Fujian Normal University, Fuzhou 350007, China; 2.State Key Laboratory of Information Security, Chinese Academy of Sciences, Beijing 100039, China; Department of Mathematics, Zhengzhou University, Zhengzhou 450025, China; 3.School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China;
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