One of the major challenges for a wireless network design is the efficient authentication scheme. A mobile node (MN) attached to a WLAN and then moved into an area where the radio signal coverage from the access point (AP) does not exist. The mobile node may reconfigure itself into ad hoc mode and connect to this network. Before the mobile node using the resource, it must be verified whether legally or not. But in Mobile IP protocol, every mobile node must perform the home registration to register with HA every second. If the foreign network is far from the home network, the authentication time delay will be long. To reduce the time delay of authentication and home registration, we provide an efficient registration scheme. We use local authentication to achieve efficiency, and use Mobile IPv6 to support the mobility.