Abstract: The invention consists of an authentication protocol for the Home Agent to authenticate and authorize the Mobile Node's Binding Update message. Two new mobility options compatible with RADIUS AAA are used to exchange a shared secret between the Home Agent and the Mobile Node so the Mobile Node can be authenticated. A Mobile Node-AAA authenticator option is added to the Binding Update message. The Home Agent generates the Mobile Node-AAA authenticator as a shared secret that it communicates as authentication data to the RADIUS AAA server on the home network. The RADIUS AAA server authenticates the communication and generates an Access-Accept message with a Mobile Node-Home Agent authenticator option. After receipt at the Home Agent, a Binding Update message with the Mobile Node-Home Agent authenticator option is transmitted from the Home Agent to the Mobile Node to use as an authenticator.