Wang Changda received the M. S. degree from Jiangsu University of Science and Technology, China, in 1999, and the Ph.D. degree from Jiangsu University, China, in 2006. He is now an associate professor of computer science, Jiangsu University, Zhenjiang, China. His research activity mainly focuseson information assurance. E-mail: changda@ujs.edu.cn Ju Shiguang received his M. S. degree in 1988, from Nanjing University of Science and Technology (China) and a Ph. D. degree in 1996 from National Polytechnic Institute (Mexico). He is now a professor of Jiangsu University, China. His current research interests include information security and spatial database.