Corresponding Author: Jingbo Yan, is a Ph.D. Candidate majoring in information security at Xidian University. He received his B.Sc in informationsecurity from Xidian University, China,2009. His research interestsinclude applied cryptography andcloud computing security.;YuqingZhang, is a professorin Graduate University ofChinese Academy of Sciences. He received his Ph.D degree in Cryptography from Xidian University in 2000. His research interests include cryptography, wirelesssecurity and trust management. *The corresponding author, email: zhangyq@nipc.org.cn. ;XuefengLiu, is a lecturerof Xidian University. He received his B.S. and Ph.D. degrees in information security from Xidian University, in 2007 and 2013, respectively. His research interests lie in the fields of cloud computing security and applied cryptography.