1. State Key Laboratory of Integrated Services Networks; Xidian University; Xi'an China
2. Institute of Computer Science; University of Göttingen; Göttingen Germany
3. State Key Laboratory of Cryptology; Beijing China
4. Department of Mathematics; Chaudhary Charan Singh University; Meerut India
5. Department of Information Systems and Cyber Security; University of Texas at San Antonio; San Antonio Texas USA