A wireless local area network system (100) supporting mobile radio telephony reduces the time to complete an authenticated handover from one access point (104) to another (108) by a mobile station (102) by performing some of the steps normally performed upon leaving one access point while still associated with that access point. More particularly, the mobile station causes a cryptographic key (204) to be preestablished (212) for use when handing over to a new access point. The cryptographic key is derived at the mobile station, and is also derived in the WLAN infrastructure and stored until the mobile station initiates a handover.
A method and system for performing pre-authentication across inter-subnets. A pre-authentication request is received by a first access point associated with a first subnet from a mobile node requesting that is requesting pre-authentication with a second access point associated with a second subnet. The request is forwarded by the access point to a first authenticator that is the authenticator for the first subnet. The first authenticator obtains from a root infrastructure node the address for a second authenticator that is the authenticator for the second access point. The first authenticator then pre-authenticates the mobile node with the second authenticator by sending a message to the address for the second authenticator.
A method and apparatus for providing improved security and improved roaming transition times in wireless networks. In the present invention, the same pairwise master key (PMK) from an authentication server can be used across multiple access points and a new pairwise transition key (PTK) is derived for each association of a station to any of the access points. A plurality of access points are organized in functional hierarchical levels and are operable to advertise an indicator of the PMK cache depth supported by a group of access points (N) and an ordered list of the identifiers for the derivation path. Access points in each level in the cache hierarchy compute the derived pairwise master keys (DPMKs) for devices in the next lower level in the hierarchy and then deliver the DPMKs to those devices. An access point calculates the PTK as part of the security exchange process when the station wishes to associate to the access point. The station also computes the PTK as part of the security exchange process. The station calculates all the DMPKs in the hierarchy as part of computing the PTK. The method and apparatus of the present invention allows the cache depth to vary per station, but it remains constant for a given station within a key circle.
A wireless network is connectable to an authentication server. Each access point in the wireless network includes a supplicant processing unit, an authenticator processing unit, and a function selector. When an access point is detected within communication range, the function selector selects either the supplicant processing unit or the authenticator processing unit. The selected unit operates to carry out or mediate an authentication protocol and establish a secure wireless link, protected by a pairwise encryption key, between the two access points. Because every access point can operate as either an authenticator or a supplicant, it is not necessary to invoke the services of a master authenticator. If an encryption key is compromised, the effect is limited and does not force the entire network to be shut down.
