中文摘要：

E-mail： 2008xiujie@ 163.com Xiujie Zhang the School of is a PhD candidate at Computer Science and Engineering, University of Electronic Science and Technology of China （UESTC）. Her research interests include leakage resilient cryptosystems, forward-secure cryptosystems, and ap- plied cryptography. Chunxiang Xu received her BS, MS, and PhD from Xidian University, China, in 1985, 1988, and 2004, respectively. She is a professor at UESTC. Her research interests include information security, cloud computing security, and cryptography. Wenzheng Zhang received his MS from the 30th Research Institute of China Electronics Technology Group Corporation in 1991. He is a research fellow in the 30th Research Institute of China Electronics Technology Group Corporation. His research interests include information security. Wanpeng Li received his MS from University of Electronic Science and Technology of China （UESTC）. His current research interests include cryptography, cloud computing, and applied cryptography.