[Liu, Yi-Ning;Wang, Yan-Ping] Guilin Univ Elect Technol, Guangxi Key Lab Trusted Software, Guilin, Peoples R China.^[Wang, Xiao-Fen] Univ Elect Sci & Technol China, Sch Comp Sci & Engn, Chengdu, Sichuan, Peoples R China.^[Xia, Zhe] Wuhan Univ Technol, Sch Comp Sci, Wuhan, Hubei, Peoples R China.^[Xu, Jingfang] Cent China Normal Univ, Sch Comp, Wuhan, Hubei, Peoples R China.