Abstract:
A key distributer node for a network includes a memory device with at least one first key, at least one data communication device that can exchange data with first and second access nodes for a terminal integrated wirelessly into the network, at least one processor connected to the memory device and the data communication device, wherein functions are provided for the processor(s) that allow authentication of the terminal at the second access node in response to a key request received by the second access node, a derivation of a second key from the first key, and triggered transmission of the second key through the data communication device to the second access node. Connections to the network&#39;s first and second access nodes with security relationships can be provided for the key distributor node when using the first key.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the United States national phase under 35 U.S.C. §371 of PCT International Patent Application No. PCT/EP2011/001934, filed on Apr. 15, 2011, and claiming priority to German Application No. 10 2010 018 286.9, filed on Apr. 26, 2010. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    Embodiments are typically in the field of wireless networks. 
       Background of Related Art 
       [0003]    Wireless networks are increasingly being used in homes and offices. Mesh networks are wireless networks with a flexible topology. Meshable nodes of a mesh network have features to detect topology changes or to establish fallback routes. 
         [0004]    For the Internet, real-time applications such as Voice-over-IP (VoIP) or Video-on-Demand (VoD) are known. Endpoints of real-time communication are usually so-called “stations” or “clients”, i.e., non-meshable terminals. 
         [0005]    For integration into a mesh network, these terminals must be associated with access nodes of the mesh network. In response to topology changes in the mesh network or the movements of a terminal across multiple wireless cells of the mesh network&#39;s access nodes, handover procedures are provided in which the terminal associated with an access node newly associates with another access node of the mesh network. 
         [0006]    The speed of the handover procedures for real-time applications is especially critical for the quality and feasibility of such real-time applications using wireless connections. To enable real-time capabilities for non-meshable terminals, the handover procedures from one access node to another should therefore occur with the least possible lag time and packet loss. 
         [0007]    802.11 networks operate with fixed access nodes, which usually communicate with each other via wired connections. 
         [0008]    In mesh networks, communication for key distribution between access nodes is less reliable than with wired communication, due to the wireless transmission, and experiences increased delays due to multi-hop communication. This results in slower handover procedures in mesh networks. Due to the mobility of both mesh nodes and terminals or stations, handover procedures also occur more frequently in mesh networks. The mobility of both mesh nodes and terminals can lead to an increased number of handover procedures. In mesh networks, access nodes operate error-prone communication via a wireless medium, which is typically also carried out across several wireless hops. Thus, a request of a PMK-R1 key through an access node with which a terminal must newly associate requires time, and the handover is delayed. 
         [0009]    The IEEE 802.11F standard indicates handover mechanisms in 802.11 networks and is documented in IEEE Trial-Use Recommended Practice for Multi-Vendor Access Point Interoperability via an Inter-Access Point Protocol Across Distribution Systems Supporting IEEE 802.11 Operation, 2003. It does not include any mechanisms for optimizing a handover procedure. 
         [0010]    The 802.21 standard concerns the communication and execution of a handover procedure between heterogeneous networks and is documented in Standard for Media Independent Handover Services, IEEE Computer Society/Local and Metropolitan Area Networks, Draft 802.21-Standard, 2004. 
         [0011]    Bruce McMurdo, Cisco Fast Secure Roaming, 2004 demonstrates an acceleration of authentication after initiating a handover. 
         [0012]    To speed up handover procedures, the utilization of several interfaces is demonstrated in Catherine Rosenberg, Edwin K. P. Chong, Hosame Abu-Amara, Jeongjoon Lee, Efficient Roaming over Heterogeneous Wireless Networks, Proceedings of WNCG Wireless Networking Symposium, 2003. To this end, authentication with the new access node is already carried out while the station is still connected to the old node via the second interface. 
         [0013]    A standardization for fast handover procedures in wireless 802.11 networks is shown in Draft Amendment to Standard for Information Technology—Telecommunications and Information Exchange between Systems—LAN/MAN Specific Requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Amendment 2: Fast BSS Transition, D2.0, March 2006. 
         [0014]    According to the IEEE 802.11r standard, a special key hierarchy is used in wireless 802.11 networks in order to optimize handover procedures. This standardized version of key distribution, in which a node is adapted as in the preamble in claim  1 , is such that a security relationship with the PMK-R0 key holder must be requested first at the Mobility Domain Controller (MDC), before a PMK-R1 key can be transferred for the handover procedure. This delays the handover procedure. 
         [0015]      FIG. 2  schematically illustrates communication in a handover procedure according to the IEEE 802.11r standard. 
         [0016]    After its initial registration, each access node calculates a PMK-R0 key within a mobility domain. Using a mobility domain controller MDC, it establishes a security relationship with a PMK-R0 key holder. After successful authentication, said key holder is derived from the negotiated master key and is stored on the access node MAP 1 , where the new access node MAP 2  logs on for the first time. This access node MAP 1  is also referred to as PMK-R0 key holder. Then, a so-called PMK-R1 key, which forms the basis for protecting the communication between access nodes and a terminal STA, is derived from the PMK-R0 key. 
         [0017]    The new meshable access node MAP 2  receives an authentication request from the terminal STA, which initiates the handover procedure. If the terminal STA initiates a handover procedure in a step S 1 , then the new access node MAP 2  establishes a security relationship with the access node MAP 1 , which is the PMK-R0 key holder, in a step S 0  using the mobility domain controller MDC. There, in a step S 2 ′, it requests its “own” PMK-R1 key, which serves as the basis for the protection of the new communication relationship between the terminal STA and the new access node MAP 2 . To this end, in a step S 3 ′ the access node MAP 1  derives the PMK-R1 key from the PMK-R0 key, and in a step S 4 ′ it transmits the PMK-R1 key to the new access node MAP 2 . The new access node MAP 2  then transmits an authentication response to the terminal in a step S 5 ′, whereupon the terminal associates with the new access node MAP 2  in a step S 6  such that the handover procedure can be concluded successfully without renewed authentication of the terminal. 
       BRIEF SUMMARY OF THE INVENTION 
       [0018]    Although doing so is not required by the claims unless stated therein, we desire to improve the speed and/or quality of a handover procedure between a first and a second or new access node for a terminal that is integrated wirelessly into the network, and to simplify that handover procedure. 
         [0019]    To this end, embodiments of the invention concern a key distributer node for a mesh network, which comprises:
       a) a memory device having at least one first key derived from a master key for all terminals to be incorporated into the mesh network,   b) at least one data communication device that can exchange data with first and second access nodes for a terminal integrated wirelessly into the mesh network,   c) at least one processor connected to the memory device and the data communication device,
 
wherein functions are provided for the processor(s) that allow authentication of the terminal at the second access node in response to a received key request from the second access node,
   d) a second key, to be derived from the first key stored in the memory device, and   e) triggered transmission of the second key through the data communication device to the second access node.       
 
         [0025]    According to an embodiment of the invention, the key distributor node has connections to the mesh network&#39;s first and second access nodes with security relationships that are already established when the key request is received by the second access node when using the first key. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0026]    Aspects and an exemplary embodiment of the invention are described below with reference to the figures, in which: 
           [0027]      FIG. 1  schematically illustrates a key distributor node; 
           [0028]      FIG. 2  schematically illustrates a communication in a handover procedure according to the IEEE 802.11r standard; 
           [0029]      FIG. 3  schematically illustrates a communication in a handover procedure according to the invention; 
           [0030]      FIG. 4  illustrates a network according to the invention. 
       
    
    
     LIST OF REFERENCE NUMBERS 
       [0000]    
       
           1  Memory device 
           2  Data communications device 
           3  Processor 
           4  BUS 
         AS Authentication server 
         STA Terminal 
         MAP 1  First access node 
         MAP 2  Second access node 
         MDC Mobility domain controller 
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0040]    Embodiments of the invention concern a key distributor node for a network, which is connected to first and second access nodes in the network for a terminal device that is integrated wirelessly into the network. Embodiments also relate to a combination of that node and the first and second access nodes. Embodiments further concern a network comprising this combination and the terminal device. Embodiments may relate a method for authenticating the terminal device in the network and a computer program with features for implementing the method. Embodiments can be used in a Voice-over-IP application and a Video-on-Demand application, in particular in a local network, especially a WLAN. Embodiments can be used specifically in mesh networks. 
         [0041]    The first key can therefore be a PMK-R0 key. 
         [0042]    Using the node according to the invention eliminates the communication designated as S 0  in  FIG. 2  and its related handover procedure delays. 
         [0043]    The key distributor node can be an authentication server, for example. 
         [0044]    If there is an authentication server, it can be used to store the PMK-R0 key. In that case, the PMK-R0 key holder would then be the authentication server, and no longer an initial access node. The advantage of this is that the Mobility Domain Controller MDC shown in  FIG. 2 , used to establish a security relationship with the PMK-R0 key holder of a terminal, is no longer needed, and the entire communication between a new access node and the Mobility Domain Controller MDC can be eliminated. This reduces handover procedure delay. 
         [0045]    If there is already an authentication server in the network, it can be expanded so that the Mobility Domain Controller MDC shown in  FIG. 2  is not needed. In that case, as described in the IEEE 802.11r standard, the initial access node is no longer used as the PMK-R0 key holder, and the authentication server is used instead. This has the advantage of eliminating step S 0  in the query for a PMK-R1 key as illustrated in  FIG. 2 : establishing a security relationship with the PMK-R0 key holder. Since, in this solution, the authentication server is the PMK-R0 key holder for all stations and every access node already has a security relationship with the authentication server, it is not necessary to establish a security relationship with the initial access node in order to join the network. This eliminates the entire communication with the Mobility Domain Controller MDC, meaning that both the delay and the use of bandwidth for a handover are reduced. 
         [0046]    In one embodiment of the invention, the key distributor node is a node of the mesh network. 
         [0047]    In this embodiment, it is not necessary for all PMK-R0 keys to be consigned to a central authority, so that the entire network is not affected if there is a problem in one area. Instead, PMK-R0 keys can advantageously be consigned to multiple central authorities with replication. 
         [0048]    Most of all, in small mesh networks, it is advantageous to eliminate the need for hardware resources such as an authentication server and instead use a designated node for key distribution. Proprietary solutions that provide for initial authentication by means of technical features such as the MAC address of a terminal or by physically installing a root key, using USE sticks, for example, can therefore be implemented. 
         [0049]    Also, in larger mesh networks with authentication servers, such designated nodes can be used, for example, in such a way that a central node plays the role of “authenticator” for each authentication. In such cases, in which there are additional designated nodes in the network with which each node is connected, expansion is possible such that each designated node plays the role of PMK-R0 key holder, instead of having an authentication server. 
         [0050]    The first and second keys are preferably symmetrical key pairs, also called PMK. 
         [0051]    The invention also concerns the combination of at least one key distributor node according to the invention and the aforementioned first and second access nodes. 
         [0052]    In a preferred embodiment of the combination according to the invention, the first and second access nodes are nodes in a mesh network. 
         [0053]    The combination according to the invention can form a mesh network with the terminal or multiple terminals. 
         [0054]    One method of authenticating the terminal during a handover procedure in the mesh network according to the invention comprises the following sequential steps:
       The mesh network terminal receives an authentication query through the second access node of the combination according to the invention,   The second key is requested at the key distributor node through the second access node,   Functions d) and e) of the invention&#39;s key distributor node are performed,   The second key is transmitted through the key distributor node&#39;s data communication device to the second access node,   An authentication response is transmitted through the second access node to the terminal,   The terminal is connected with the second access node.       
 
         [0061]    According to one embodiment of the invention, the preceding steps S 1 -S 6  are performed if the terminal is located in a wireless cell overlap area of the first and second access nodes. 
         [0062]    It is possible to configure the nodes with a storage device, wherein an initial authentication of the first and/or second access node is preferably performed before step S 1  at the key distributor node, specifically by storing the first key in the storage device. 
         [0063]    The invention also includes a computer program with features corresponding to a method according to the invention. 
         [0064]    The invention can be used in a real-time network application such as a Voice-over-IP application or a Video-on-Demand application and/or in a local network, especially a WLAN. 
         [0065]    In the invention&#39;s key distributor node shown in  FIG. 1 , a processor  3  is connected to a memory device  1  and a data communication device  2  via a BUS  4 . 
         [0066]    This key distributor node is used in a network illustrated in  FIG. 4  as the authentication server and is connected to first and second access nodes MAP 1 , MAP 2  via the data communication device  2 . The network has the key distribution and handover functions described below with respect to  FIGS. 3 and 4 . 
         [0067]      FIG. 3  illustrates the process of a handover to the aforementioned new access node MAP 2 . The PMK-R1 key is requested directly at the authentication server AS, and the handover procedure can then be successfully completed. The authentication server AS is accessible only to privileged users and is therefore well protected. 
         [0068]    The network shown in  FIG. 4  comprises two meshable access nodes, only one of which, MAP 2 , is illustrated in  FIG. 3  and both of which were already authenticated via the authentication server AS when admitted to the mesh network, so that there is a security relationship with them. A mobile terminal STA in the form of a notebook computer is authenticated via the access node MAP 2 , which forwards the authentication information to the authentication server AS. The authentication server AS verifies the access authorization and generates a master key upon successful authentication of the access node. From that master key, it derives the PMK-R0 key, which it stores in its function as the local PMK-R0 key holder. In the state of the art according to the IEEE 802.11r standard, the initial access node fulfills the function of the PMK-R0 key holder for the station. In relation to the storage of the PMK-R0 key, the authentication server AS generates a PMK-R1 key and transmits it back to the requesting access node MAP 2 . This PMK-R1 key contains certain information about the access node MAP 2 , such as its MAC address, and thus forms the basis for protecting the communication relationship between the access node MAP 2  and the terminal STA which is now associated with the mesh network via the access node MAP 2 . 
         [0069]    In the network topology shown in  FIG. 4 , the terminal is associated with the access node MAP 1  and moves in the direction of the arrow shown in  FIG. 4  in a wireless cell of the access node MAP 2 . At a specific point in time, the terminal initiates a related handover procedure from access node MAP 1  to access node MAP 2 . The optimum time for such a handover is assumed here to be preset. After initiating the handover procedure, MAP 2  must request a PMK-R1 key from the terminal&#39;s PMK-R0 key holder through the station STA, in order to be able to establish a security relationship with the terminal. To do this, a security relationship is first required between the PMK-R0 key holder and the new access node MAP 2 . In the original standard, the new access node MAP 2  had to request such a security relationship with the initial access node MAP 1  from the Mobility Domain Controller MDC. MAP 1  could not transmit a PMK-R1 key to MAP 2  until that connection was made. The proposed invented solution shortens the communication by one “cycle length,” because with this solution the authentication server AS performs the function of the PMK-R0 key holder. The new access node MAP 2  thus requests the PMK-R1 key required for the handover from the authentication server AS, with which it already has a security relationship. The query illustrated in  FIG. 2  for a security relationship with the MDC is therefore omitted. In response to the query from MAP 2 , the authentication server AS transmits a MAP 2 -specific PMK-R1 key to the new access node MAP 2 , which is used as the basis for protecting the communication relationship between MAP 2  and the terminal STA, making it possible to complete the handover procedure. 
         [0070]    The authentication comprises the following sequential steps:
       The network terminal STA receives an authentication query through the second access node MAP 2  of the combination according to the invention,   The second key PMK-R1 is requested at the server AS through the second access node MAP 2 ,   To authenticate the terminal (STA) at the second access node MAP 2 , the second key is derived from the first key,   The second key PMK-R1 is sent to the second access node MAP 2 ,   An authentication response is transmitted through the second access node MAP 2  to the terminal STA,   The terminal STA is associated with the second access node MAP 2 .       
 
         [0077]    Special Advantages of Invention Embodiments 
         [0078]    If there is an authentication server, there is no need for communication with the Mobility Domain Controller to establish a security relationship with the PMK-R0 key holder of a station, since the authentication server, which has already set up a security relationship with all access nodes, handles the management and storage of the PMK-R0 key. Such a feature prevents delays caused by requesting the PMK-R1 key required for a handover procedure. Thus, it is possible to further speed up a handover procedure in mesh networks, and real-time applications such as Voice-over-IP can be better supported.