Since network services are provided cooperatively by multiple servers in the lnternet, the authentication protocols for multiserver architecture are required by Internetbased services, such as online game, online trad...Since network services are provided cooperatively by multiple servers in the lnternet, the authentication protocols for multiserver architecture are required by Internetbased services, such as online game, online trade and so on. Recently, Li et al. analyzed Lee et al.＇s protocol and proposed an improved dynamic identity based authentication protocol for multi-server architecture. They claimed that their protocol provides user＇s anonymity, mutual authentication and the session key agreement against several kinds of attacks. In this paper, a cryptanalysis on Lee et al.＇s scheme shows that Lee et al＇s protocol is also vulnerable to malicious server attack, stolen smart card attack and leak-of-verifier attack. Moreover, Li e/ al.＇s improved protocol is also vulnerable to all these attacks. Further cryptanalysis reveals that Li et al.＇s improved protocol is susceptible to collusion attack.展开更多
The understanding and prediction of preferential fluid flow in porous media have attracted considerable attention in various engineering fields because of the implications of such flows in leading to a non-equilibrium...The understanding and prediction of preferential fluid flow in porous media have attracted considerable attention in various engineering fields because of the implications of such flows in leading to a non-equilibrium fluid flow in the subsurface. In this study, a novel algorithm is proposed to predict preferential flow paths based on the topologically equivalent network of a porous structure and the flow resistance of flow paths. The equivalent flow network was constructed using Poiseuille's law and the maximal inscribed sphere algorithm. The flow resistance of each path was then determined based on Darcy's law. It was determined that fluid tends to follow paths with lower flow resistance. A computer program was developed and applied to an actual porous structure. To validate the algorithm and program, we tested and recorded two-dimensional(2 D) water flow using an ablated Perspex sheet featuring the same porous structure investigated using the analytical calculations. The results show that the measured preferential flow paths are consistent with the predictions.展开更多
基金supported by the Key Program of NSFC-Guangdong Union Foundation under Grant No.U1135002Young Foundation of Humanities and Social Sciences of MOE (Ministry of Education in China) of under Grant No.11YJCZH160Foundation for Young Scientists of Jiangxi Province of China under Grant No.20133BCB23016
文摘Since network services are provided cooperatively by multiple servers in the lnternet, the authentication protocols for multiserver architecture are required by Internetbased services, such as online game, online trade and so on. Recently, Li et al. analyzed Lee et al.＇s protocol and proposed an improved dynamic identity based authentication protocol for multi-server architecture. They claimed that their protocol provides user＇s anonymity, mutual authentication and the session key agreement against several kinds of attacks. In this paper, a cryptanalysis on Lee et al.＇s scheme shows that Lee et al＇s protocol is also vulnerable to malicious server attack, stolen smart card attack and leak-of-verifier attack. Moreover, Li e/ al.＇s improved protocol is also vulnerable to all these attacks. Further cryptanalysis reveals that Li et al.＇s improved protocol is susceptible to collusion attack.
基金supported by the National Natural Science Foundation of China(Grants Nos.51374213,51674251&51727807)the State Key Research Development Program of China(Grant No.2016YFC0600705)+2 种基金the National Natural Science Fund for Distinguished Young Scholars(Grant No.51125017)the Fund for Creative Research and Development Group Program of Jiangsu Province(2014-27)the Priority Academic Program Development of Jiangsu Higher Education Institutions(Grant No.PAPD-2014)
文摘The understanding and prediction of preferential fluid flow in porous media have attracted considerable attention in various engineering fields because of the implications of such flows in leading to a non-equilibrium fluid flow in the subsurface. In this study, a novel algorithm is proposed to predict preferential flow paths based on the topologically equivalent network of a porous structure and the flow resistance of flow paths. The equivalent flow network was constructed using Poiseuille's law and the maximal inscribed sphere algorithm. The flow resistance of each path was then determined based on Darcy's law. It was determined that fluid tends to follow paths with lower flow resistance. A computer program was developed and applied to an actual porous structure. To validate the algorithm and program, we tested and recorded two-dimensional(2 D) water flow using an ablated Perspex sheet featuring the same porous structure investigated using the analytical calculations. The results show that the measured preferential flow paths are consistent with the predictions.
