WANG Chao, received his B.S. and M.S. degrees in Mechanical Design & Theory from Hefei University of Technology, China in 1999 and 2002, respectively, obtained his Ph.D. degree in Computer Application Technology from Xidian University, China in 2006. He is currently an Associate Professor in Xidian University, China. His research areas include SNS and information security. Email: wangchao@xidian.edu.cn. HU Yuanping, received her B.S. degree in Software Engineering from Xidian University, China in 2012. She is a postgraduate student of Xidian University, Her current research interests include SNS and information security. LIU Chengyuon, received his B.S. degree in Information and Computing Science from Northwest University, China in 2012. He is a postgraduate student of Xidian University. His current research interests include SNS and information security. LIU Zhihong, received his B.S. degree in Mathematics from National University of Defense Technology, China in 1989, M.S. degree in computer and its applications from Air Force Engineering University, China in 2001, and Ph.D. degree in Cryptography from Xidian University, China in 2009. He is currently an Associate Professor in Xidian University, China. His research areas include mobile computing and information security. MA Jianfeng, received his B.S. degree in mathematics from Shaanxi Normal University, China in 1985, and obtained his M.S. and Ph.D. degrees in computer software and communications engineering from Xidian University, China in 1988 and 1995, respectively. From 1999 to 2001, he was with Nanyang Technological University of Singapore as a research fellow. He is an IEEE member and a senior member of Chinese Institute of Electronics (CIE). Now he is the director and Changjiang Scholars Distinguished Professor of School of Computer Science at Xidian University, China. His current research interests include distributed systems, wireless and mobile computing systems, computer networks, and information and network security.