作者机构:[1]Laboratory of Computer Networks & Information Security, Ministry of Education, Xi'dian University, Xi'an 710071, China, [2]Xi'an Research Institute of Hi-Tech, Xi 'an 710025, China
相关基金:Acknowledgements: This research was supported in part by the Nature Science Foundation of China (No. 60473029) and the Open foundation of Beijing Institute of Electronic Science and Technology. The authors would like to thank WANG Bao-cang, QUAN Yi-ning, DONG Li-hua and CHEN Jie for their critical review of the manuscript.