1. College of Liberal Arts and SciencesNational University of Defense TechnologyChangsha410073China
2. Hunan Engineering Research Center of Commercial Cryptography Theory and Technology InnovationChangsha410073China
3. State Key Laboratory of Information SecurityInstitute of Information Engineering, Chinese Academy of SciencesBeijing100093China
4. College of Information and CommunicationNational University of Defense TechnologyWuhan430010China