1. School of Mathematics and Computational Science, Xiangtan University, Xiangtan, China
2. Key Laboratory of Hunan Province for Internet of Things and Information Security and the Key Laboratory of Intelligent Computing and Information Processing of Ministry of Education, College of Computer Science, Hunan International Scientific and Technological Cooperation Base of Intelligent Network, Xiangtan University, Xiangtan, China
3. College of Computer Science and Electronic Engineering, Hunan University, Changsha, China
4. School of Information Technology, Deakin University, Waurn Ponds, Geelong, VIC, Australia
5. National Computer Network Emergency Response Technical Team/Coordination Center of China, Beijing, China