The rapid spread of new radio access technologies and the consequent service opportunities have stimulated thetechnical and scientific community to investigate future evolution scenarios for 3rd Generation networks (3G), generically referred to as Beyond-3G or 4G. They are going to be characterized by ever stronger requirements for security, as well as the capability for the final users to experience continuous connectivity and uninterrupted services of IP applications as they move about from one access network to another. Key issues are: i) securityprovision for applications exchanging data in diverse wireless networks; ii) seamless mobility (handoff) between different coverage domains and, in case, access technologies. Since many proposal...