A method is provided for securing a PMIP tunnel between a serving gateway and a new access node through which an access terminal communicates. A PMIP key hierarchy unique to each access terminal is maintained by the gateway. The gateway uses a first node key to secure PMIP tunnels when authentication of the access terminal has been performed. A PMIP key is generated based on the first node key and the PMIP key is sent to the new access node to assist in establishing and securing a PMIP tunnel between the gateway and the new access node. Otherwise, when authentication of the access terminal has not been performed, the gateway generates a second node key and sends it to an intermediary network node which then generates and sends a PMIP key to the new access node. This second key is then used to secure the PMIP tunnel.