[1] College of Information Technology, Hebei Normal University, No. 20, South ErHuan Road, YuHua District, Shijiazhuang
[2] Shaanxi Key Laboratory of Network and System Security, Xidian University, No. 2, TaiBai South Road, YanTa District, Xi'an
[3] Network and Information Center, Guizhou University, No. 242, Huaxi Street, HuaXi District, Guiyang
[4] Network and Information Center, Yunnan University, No. 2, Cuihu North Road, WuHua District, Kunming