Abstract:
A Security Association establishment negotiation technique includes forwarding identifying information from a Mobile Node via a first interface to a first network element. Negotiations are then initiated between the first network element and a second network element serving as a proxy for the Mobile Node via a second interface to establish a Security Association between the Mobile Node and the first network element, the second network element utilizing previously stored Security Association parameters of the Mobile Node. Upon agreement between the first network element and the second network element with regard to the Security Association parameters, the first network element forwards the agreed-upon Security Association parameters to the Mobile Node via the first interface. The first network element may include a Home Agent, a Correspondent Node or a Agent, and the first interface may include a wireless interface to forward information between the Mobile Node and the first network element. The first network element may also include a first gateway connected to it. The first gateway may include a AAA (Authentication, Authorization, and Accounting) server. The second network element may include a second gateway and an Subscriber database/Authentication Center, and the second gateway may be connected to the Subscriber database/Authentication Center. The second gateway may also include a AAA server.

Description:
FIELD 
     The present invention relates to wireless terminals and more particularly to a technique for efficiently negotiating security associations establishment between a Mobile Node connected to the wireless terminal and different network entities. 
     BACKGROUND OF THE INVENTION 
     In wireless networks, such as cellular networks, Mobile Nodes such as cellular telephones must establish security associations with different network entities. Establishing a Security Association between a Mobile Node and a network entity means deciding a set of parameters describing the Security Association. In particular, it may mean deciding what security algorithms, such as encryption, integrity protection, authentication and key derivation algorithms, are to be used for communications over the wireless interface. It may also mean deciding how these algorithms are to be used and in what cases, what keys are to be used with the algorithms, how additional keys to be used in the Security Association are to be derived, the lifetime of the Security Association and of the keys established in the Security Association. 
     For example, in future cellular networks, the Mobile Node will have to dynamically establish security associations with various different network entities. 
     The following describes a list of security associations that a Mobile Node may need to establish with an entity; but this list is provided to illustrate the current application. This latter is not restricted to the following scenarios. 
     The Mobile Node and the serving system must agree on the aspects of a Security Association mentioned above for communications over the wireless interface with a network entity. 
     If the network is a mobile IPv4 (Internet Protocol) based cellular network, the Mobile Node and the Foreign Agent may have to establish a Security Association. 
     If the network is a mobile IP (Internet Protocol) based cellular network, and the Home Agent is dynamically assigned, then the Mobile Node and the assigned Home Agent must set up a Security Association. Furthermore, if the network is a mobile IP based cellular network, then the Mobile Node and the Corresponding Node may also have to set up such a Security Association in order to use Route Optimizations. 
     If a Localized Mobility Management scheme such as MIPv6RR (Mobile lpv6 Regional Registration) or HMIPv6 (Hierarchical Mobile lpv6) is used, the Mobile Node and the Agents in the visited domain must share a Security Association. Thus, as noted above, there are many cases in which the Mobile Node needs to set up a Security Association with one or more Network Entities in the visited domain. In order to setup such a Security Association, the Mobile Node needs to indicate to the Network Entities the list of parameters describing the Security Association mentioned above that it supports. 
     The messages sent by the Mobile Node containing the above noted information can be long since the Mobile Node must define the capabilities it supports and must send some specific proposals to the Network Entities. The Mobile Node and the Network Entities may sometimes exchange many messages before agreeing on specific parameters of the Security Association as described above. Accordingly, the negotiations needed to set up the Security Associations are extensive and therefore not efficient for cellular networks or other wireless networks where the radio resources are limited and expensive. 
     SUMMARY OF THE INVENTION 
     In the efficient security association establishment negotiation technique of the present invention, negotiations over the wireless link between the Mobile Node and a Network Entity are avoided to conserve limited radio resources. This is achieved by having a negotiation between such a Network Entity and a network element in the home domain/network acting as a proxy on behalf of the Mobile Node in the establishment of a Security Association between the Mobile Node and a Network Entity. 
     A security association establishment negotiation technique in accordance with the present invention includes forwarding identifying information from a Mobile Node via a first interface to a first network element. Negotiations are then initiated between the first network element and a second network element acting as a proxy for the Mobile Node via a second interface to establish a security association between the Mobile Node and the first network element, the second network element utilizing previously stored Security Association parameters and preferences of the Mobile Node. Upon agreement between the first network element and the second network element with regard to the Security Association parameters, the first network element forwards the agreed-upon Security Association parameters to the Mobile Node via the first interface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and a better understanding of the present invention will become apparent from the following detailed description of example embodiments and the claims when read in connection with the accompanying drawings, all forming a part of the disclosure of this invention. While the foregoing and following written and illustrated disclosure focuses on disclosing example embodiments of the invention, it should be clearly understood that the same is by way of illustration and example only and the invention is not limited thereto. This spirit and scope of the present invention are limited only by the terms of the appended claims. 
       The following represents brief descriptions of the drawings, wherein: 
         FIG. 1  illustrates an example of a Security Association establishment between a Mobile Node and an Agent in accordance with the present invention. 
         FIG. 2  illustrates an example of an environment in which the technique in accordance with the present invention may be used. 
         FIG. 3  illustrates an example of a negotiation to establish a Security Association in accordance with the present invention. 
         FIG. 4  illustrates another example of a negotiation to establish a Security Association in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Before beginning a detailed description of the subject invention, mention of the following is in order. When appropriate, like reference numerals and characters may be used to designate identical, corresponding, or similar components in differing drawing figures. Further, in the detailed description to follow, example sizes/models/values/ranges may be given, although the present invention is not limited thereto. Lastly, the details of various elements which are defined by currently used industry standards have not been included for simplicity of illustration and discussion as so as not to obscure the invention. However, where known, these standards will be cited in the specification and are incorporated by reference herein in their entirety. 
       FIG. 1  illustrates an example of a Security Association establishment between a Mobile Node and an Agent in accordance with a present invention. The following text contains a list of scenarios to identify different types of agents. The list is not exhaustive and the current application is not to be considered restricted to the following scenarios. As an example, if a security association is required to protect data over the access link between the Mobile Node and the Access Router, the Agent can be the Access Router. In the same way, if the network is a Mobile IP (Internet Protocol) based cellular network, and the Mobile IP Home Agent is dynamically assigned for the Mobile Node, the Agent can be the Home Agent. If the network is in particular a Mobile IPv4 based cellular network, the Agent can be the Foreign agent. Again, if the network is a Mobile IP based cellular network, then the Mobile Node and the Corresponding Node may also have to set up a Security Association in order to implement Mobile IP mechanisms such as route optimizations. Finally, if a Localized Mobility Management scheme such as MIPv6RR or HMIPv6 is used, the Mobile Node and the Agents in the visited domain must share a Security Association. 
     In  FIG. 1 , a Mobile Node  100  shares knowledge of the parameters describing the Security Associations supported by the Mobile Node and the Mobile Node preferences regarding selection of the Security Association parameters with one or more entities in its home domain, in this case a Home AAA (Authentication, Authorization, and Accounting) Server  120  and/or a Policy Server  130 . 
     The parameters describing the Security Associations types that the Mobile Node supports and that are shared by the Mobile Node  100  and the Home AAA Server  120  and/or Policy Server  130  may include but are not limited to: what security algorithms, such as encryption, integrity protection, authentication and key derivation algorithms, are to be used for communications over the wireless interface; how these algorithms are to be used and in what cases; what keys are to be used with the algorithms; how additional keys to be used in the Security Association are to be derived; the lifetime of the Security Association and of the keys established in the Security Association. 
     As noted in  FIG. 1 , a Mobile Node  100  sends its identity and indications of the Security Associations it needs to establish with a network entity via a connection that may include a wireless link to an Agent  110 . The network entity, in this case the Agent  110 , then contacts an entity in the Mobile Node&#39;s home domain, in this case a Home AAA (Authentication, Authorization, and Accounting) Server  120 . The Agent  110  sends the identity of the Mobile Node and, optionally, its own security policies and capabilities to the Home AM Server  120 . That is, the Agent  110  informs the Server  120  that a security association between the agent and the Mobile Node identified by the identity is requested The Agent  110  may also send to the Server  120  a list of proposals of parameters of the Security Associations it prefers to use with the Mobile Node  100 . 
     Thus, rather than the Mobile Node  100  conducting the negotiations needed for the establishment of the required Security Associations with the Agent  110 , the Agent  110  conducts negotiations with the Server  120 . In the home domain of the Mobile Node  110 , the capabilities of the Mobility Agent  110  are compared with those of the Mobile Node  100  by the Server  120  or by the Server  130 . The Server  120  or the Server  130  acts as a proxy for the Mobile Node by conducting the negotiations with the Agent  110  and making a decision on the parameters of the Security Association according to the Mobile Node preferences. Several messages may be exchanged between the Mobility Agent  110  and the Server  120  or Server  130  prior to the final decision. 
     The Agent  110  then passes the choice/decision of the Server  120 , that is, the parameters describing the selected Security Association, to the Mobile Node  100 . 
     Note that the details of the various parameters transferred during negotiations between the Agent  110  and the Server  120  have not been discussed in detail since they are clearly defined in various industry groups standards. For example, the IETF (Internet Engineering Task Force), which publishes numerous industry standards on its Internet site at www.ietf.org, has published Internet Security Association and Key Management Protocol (rfc  2408 ) and the Internet Key Exchange (rfc  2409 ) which are relevant to the above noted negotiations. They have also published numerous AAA standards, such as AAA Solutions, Criteria for Evaluating an AAA Protocols for Network Access, and Authentication, Authorization, and Accounting: Protocol Evaluation. All of these standards are incorporated herein by reference in their entirety. 
     Furthermore, while present day cellular networks authenticate a user based on symmetric key mechanisms, future cellular networks will also have the option to use Public Key authentication mechanisms and for the key distribution, many mechanisms, such as the Diffie Hellman procedure, will become possible. Accordingly, in accordance with the technique of the present invention, after the Mobile Node sends its identity to the network entity, such as the Agent, the Agent can communicate with the home domain, that is, the Home AAA Server, and learn from the Home AAA Server what parameters describing a Security Association the Mobile Node supports. Thus, the technique in accordance with the present invention offers is the possibility of many types of Security Associations. 
       FIG. 2  illustrates an example of an environment in which the technique in accordance with the present invention may be used. As illustrated in  FIG. 2 , a mobile terminal (Mobile Node)  200  is connected via a wireless interface to an Agent  210  of a Visited Network  220  which is connected to a Visited Gateway (GW)  230  connected to a Home Gateway  240  of a Home Network  250 . A Subscriber database/Authentication Center  260  is disposed within the Home Network  250  and is connected to the Home GW  240 . 
     It is assumed that there is a pre-established Security Association between the Visited GW  230 , which can be the Visited AAA Server, and the Agent  210 . This Security Association may, for example, be set up offline through manual key entry, Internet Key Exchange Protocol or a Key Distribution Server specific to the Visited Network  220 . This provides security internally to the network so that the operator can choose the level and type of security to be implemented in its network. 
     Similarly, there is another pre-established Security Association between the Subscriber database/Authentication Center  260  and the Home GW  240 . This Security Association may be established in the same fashion as that noted above and also serves to provide security internally to the network. 
     Furthermore, there is still another pre-established Security Association between the Home GW  240  and the Visited GW  230 . This Security Association may be established offline through a roaming agreement or via an automatic protocol according to industry standards. 
     The Mobile Node  200  and the Subscriber database/Authentication Center  260  may share a long-term key Ki, common knowledge of a security function F 1  for derivation of an integrity key, common knowledge of a security function F 2  for derivation of a ciphering key, and common knowledge of a MAC function for integrity protection of data. Other keys and knowledge of algorithms may be shared by the Mobile Node  200  and the Subscriber database/Authentication Center  260 . 
       FIG. 3  illustrates an example of a negotiation to establish a Security Association in accordance with the present invention in the environment of  FIG. 2 . Referring to  FIG. 3 , the Mobile Node  200  generates a random value, RAND 1  and uses it as an input with the key Ki for two different functions F 1  and F 2  and shares it with its Home Network  250  to derive a temporal integrity key IK and a temporal ciphering key CK. That is, F 1  (Ki, RAND 1 )=IK and F 2  (Ki, RAND 2 )=CK. The Mobile Node  200  sends its identity through its NAI, for example, to the Agent  210  with the RAND 1  and a MAC for integrity protection using the IK. The Mobile Node  200  may also protect part of the message using CK encrypt it. 
     Since the message is a request for a Security Association to be set up between the Agent  210  and the Mobile Node  200  which belongs to another network, the Agent  210  forwards the message to the Visited GW  230  and may include the parameters describing the Security Associations that the Agent  230  supports. In addition, the Agent  230  may also include in the message a list of proposals of parameters of the Security Associations it prefers to use with the Mobile Node  200 . 
     The Agent  210  can determine that the Mobile Node  200  belongs to another network by analyzing the realm part of the NAI, for example. This message is secured due to the Security Association between the Agent  210  and the Visited GW  230 . 
     The Visited GW  230  then transmits this request to the Home GW  240  of the Mobile Node  200  due to the realm part of the NAI, for example, and this message is protected by the Security Association established between the Visited GW  230  and the Home GW  240 . 
     The Home GW  240  then forwards the message to the Subscriber database/Authentication Center  260 . The message is protected using the appropriate Security Association established therebetween. 
     The Subscriber database/Authentication Center  260  then retrieves the Ki based on the NAI and using the RAND 1 , derives CK and IK. It then verifies the correctness of the MAC using IK and if it succeeds, the Subscriber database/Authentication Center  260 , on behalf of the Mobile Node  200 , starts the negotiations of the different parameters of a Security Association with the Agent  210 . These message exchanges are protected due to the various established Security Associations between the Agent  210  and the Visited GW  230  and between the Visited GW  230  and the Home GW  240 , etc. 
     The Subscriber database/Authentication Center  260  will determine, from a database, which Security Association parameters are to be used, based on the parameters for Security Associations that the Mobile Node  200  supports. 
     Note that there may be several round-trip message exchanges in the negotiation, which may occur before there it is agreement with respect to all of the different parameters. Any agreed-upon industry standard protocol may be used for the Security Association. 
     Once the Subscriber database/Authentication Center  260  and the Agent  210  have agreed on the different parameters describing the Security Association to be used with the Mobile Node  200 , the Subscriber database/Authentication Center  260  will send the parameters to the Agent  210  utilizing the previously established Security Associations to protect and authenticate them and will also inform the Mobile Node  200  using CK and IK to secure the parameters. The Mobile Node  200  and its Home GW  240  can use flags or some data fields to carry data. However, no standardization thereof may be required since the data is being sent from the Mobile Node  200  to its Home GW  240 . The Subscriber database/Authentication Center  260  may also generate another random value RAND 2  and send it to the Mobile Node  200  using the random value RAND 1 . 
     The Mobile Node  200  may use both CK and IK to decrypt/authenticate the message received from its Home GW  240  and set up the Security Association according to the contents of the message. 
       FIG. 4  illustrates another example of a negotiation to establish a Security Association in accordance with the present invention. In the example shown in  FIG. 3 , the Subscriber Database and Authentication Server  260  is aware of the keys used by the Mobile Node  200 , which may not be acceptable in certain cases. That is, the Mobile Node  200  may not want anyone other than the entity that it is communicating with to know the keys that are being used. As shown in  FIG. 4 , it is possible for the Server  220  or the Server  230  acting as a proxy on behalf of the Mobile Node  200  to negotiate the value of the parameters of the Security Association to be used between the Mobile Node  200  and the Agent  210  without the Server  220  or the Server  230  knowing the value of the keys. For example, after the Agent  210  provides during the negotiation its Diffie Hellman public value to the Server  220  or the Server  230 , the latter may send the public Diffie Hellman value of the Agent  210  to the Mobile Node  200 .Since the Server  220  or the Server  230  does not know the Mobile Node  200  private Diffie Hellman value, it cannot determine the final value of the parameters of the Security Association. That is, the Home Network  250  is used to negotiate the different parameters of the Security Association and exchange the Diffie Hellman value in an authenticated fashion but since the Server  220  or the Server  230  does not know the Mobile Node&#39;s private value, it cannot derive the final keys. 
     This concludes the description of the example embodiments. Although the present invention has been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention. More particularly, reasonable variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the foregoing disclosure, the drawings, and the appended claims without departing from the spirit of this invention. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.