The complexity and composability of secure interoperation

Advances in distributed systems and networking technology have made interoperation not only feasible but also increasingly popular. The authors define the interoperation of secure systems and its security, and prove complexity and composability results on obtaining optimal and secure interoperation. Most problems are NP-complete even for systems with very simple access control structures. Nevertheless, composability reduces complexity in that secure global interoperation can be obtained incrementally by composing secure local interoperation. The authors illustrate, through an application, how these theoretical results can help system designers in practice.>