Method of creating security associations in mobile IP networks
View Patent ↗A key distribution scheme is provided, which is useful for establishing, distributing, and maintaining security associations in a Mobile IP network. An authentication server performs an initial validation of a new session and generates a root key which it delivers to the initial access gateway and to the home agent. The initial access gateway and the home agent each independently compute a derivative key available only to themselves. The initial access gateway, acting as proxy for the mobile station, uses the derivative key to sign the Mobile IP registration or binding update transactions, and sends the signed registration or binding update to the home agent for validation. Once the session is established between the mobile station and the home agent, the access gateways act as proxies on behalf of the mobile station to maintain the session mobility. In handoff, the new access gateway acquires the root key as part of the transferred session context. The new access gateway, acting as proxy for the mobile station, computes a new derivative key from the root key and uses it to sign a binding update.
1. A method of establishing a security binding between a home agent and an access gateway on behalf of a served mobile station in a Mobile IP network, comprising:
obtaining, at the access gateway, an initial root key from an authentication server, wherein the initial root key is used only one time to effectuate an initial security binding;
computing, at the access gateway, a derivative key, the derivative key computed as a pseudo-random function of (1) the initial root key, (2) an address of the access gateway and (3) an address of an associated home agent;
requesting, by the access gateway, a binding between the home agent and the access gateway on behalf of the mobile station wherein the derivative key is attached to the binding request for authentication of the request; and
receiving confirmation at the access gateway from the home agent that the binding request has been validated, wherein confirmation includes a next root key to be used only one time to effectuate a subsequent binding of the mobile station; and
replacing, at the access gateway, the initial root key with the next root key.
2. A method for validating a binding update for a mobile station in a Mobile IP network, comprising:
obtaining, at a home agent associated with an access gateway, an initial root key from an authentication server, wherein the initial root key is used only one time to effectuate an initial security binding;
from the access gateway, obtaining, at the associated home agent, a binding update together with a signature attached to the binding update that has been computed using a derivative key, the derivative key having been constructed as a pseudo-random function of (1) the initial root key, (2) an address of said access gateway and (3) an address of the associated home agent;
recreating, at the home agent, the derivative key from the pseudo-random function of (1) the initial root key, (2) the address of said access gateway and (3) the address of said home agent;
using the derivative key to validate the binding update signature;
generating, at the home agent, a next root key to be used only one time to effectuate a subsequent binding of the mobile station; and
replacing, at the home agent, the initial root key with the next root key.
3. The method of claim 1 , wherein the access gateway is defined as a prior access gateway, the method further comprising:
Obtaining, at a target access gateway, a transfer of a session context from the prior access gateway, wherein the transferred context includes the next root key;
using the next root key to compute a derivative key at the target access gateway, the derivative key computed as a pseudo-random function of (1) the next root key, (2) an address of the target access gateway and (3) an address of a home agent associated with the mobile station;
generating, by the target access gateway, a binding update request on behalf of the mobile station wherein the derivative key is attached to the binding request for authentication of the request;
sending the signed binding update to the home agent; and
in response to a validation of the binding update request by the home agent, accepting packets, by the target access gateway, for forwarding between the mobile station and the home agent.