The future command & control system for the Swedish Armed Forces will probably not be a single homogeneous system, but rather a collection of cooperating systems. Adding the need for the Armed Forces to cooperate with other systems - such as civilian or international - increases the demands for interoperability. The ability to cooperate with other systems is not just about communication. It requires exchange of security information between different systems. It also involves establishing trust in messages coming from other systems, as well as for other systems services. The project Systems of systems has created a model for securely transferring messages between systems. The technical basis is that of Web Services since techniques and standards have been collected from there. The model establishes trust in the sender of a message as well as for the participating Web Services. This report is a summary of all the reports produced within the project during its three years.