1. Department of Internet Finance, Qilu University of Technology, Jinan 250100, China
2. State Key Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, Beijing 100093, China
3. School of Engineering and Information Technology, University of NSW (UNSW) at the Australian Defence Force Academy (ADFA), Canberra, ACT 2600, Australia
4. School of Mathematics, Shandong University, Jinan 250100, China