1. Shaanxi Key Laboratory of Blockchain and Secure Computing, Xidian University, Xi'an, China
2. State Key Lab of ISN, Xidian University, Xi'an, China
3. Xidian Guangzhou Institute of Technology, Guangzhou, China
4. Department of Electrical and Computer Engineering, University of Windsor, Windsor, ON, Canada
5. Distributed Systems Group, Technische Universität Wien, Vienna, Austria
6. College of Computer Science and Software Engineering, Shenzhen University, Shenzhen, China