A method of establishing communication protocols between a mobile node and a home agent in a mobile communications networks. The method uses the steps of: generating, at the mobile node plural care of addresses (CoAs) and a corresponding number of security parameter indices; sending the generated CoAs and security parameter indices to the home agent in an encrypted form; generating, at the home agent, on the basis of the received CoAs and security parameter indices, an equal number of home addresses (HoAs) and associated security parameter indices; sending the list of HoAs and associated security parameter indices generated at the home agent to the mobile node, and; using the generated CoAs, HoAs and associated security parameter indices as the basis for communication protocol addresses and encryption for communication between the home agent and the mobile node. A system employing the method is also provided.