1. School of Electronic and Information Engineering, Southwest University, Chongqing, China
2. Chongqing Key Laboratory of Non-linear Circuit and Intelligent Information Processing, Southwest University, Chongqing, China
3. Illinois State University, Normal, IL, USA
4. Center of Technical Support for Network Security, Chongqing Municipal Public Security Bureau, Chongqing, China
5. College of Computer and Information Science, Southwest University, Chongqing, China