1. School of Computer and Software and the Engineering Research Center of Digital Forensics, Ministry of Education, Nanjing University of Information Science and Technology, Nanjing, China
2. School of Computer and Software, Nanjing University of Information Science and Technology, Nanjing, China
3. College of Computer Science and Technology and the MIIT Key Laboratory of Pattern Analysis and Machine Intelligence, Nanjing University of Aeronautics and Astronautics, Nanjing, China
4. School of Electrical and Electronic Engineering, The University of Manchester, Manchester, U.K.