Internet protocol based networking is gaining ground in armed forces, leading to a concept described by the NATO as network centric capabilities (NCC). The goal is to enable state-of-the-art, affordable and powerful electronic information services to the troops. A tighter connection of the forces is expected to further enhance the joined strike capabilities. Providing secure information exchange within groups of armed forces is one aspect of the NCC concept. Such group communication is enabled by the multicast feature of the IP technology. Security requirements are met by using the IP security (IPsec) architecture. IPsec enables secure communication between secure private networks via an unsecured public text network. While secure unicast t...