Synchronous Universally Composable Computer Networks

Designers of modern IT networks face tremendous security challenges. As systems grow ever more complex and connected it is essential that they resist even previously-unknown attacks. Using formal models to analyse the security of cryptographic protocols is a well-established practice. However, the security of complex networks is often still evaluated in an ad-hoc fashion. We analyse the applicability of formal security models for complex networks and narrow the gap between security proofs for abstract cryptographic protocols and real-world systems. Specifically we use the Universal Composability framework together with Katz et al.’s extensions for synchronous computation and bounded-delay channels [15]. This allows us to model availability guarantees. We propose a 5-phase paradigm for specifying protocols in a clear representation. To capture redundant formalisms and simplify defining network topologies, we introduce two functionalities \(\mathcal {F}_{\mathsf {wrap}}\) and \(\mathcal {F}_{\mathsf {net}}\). Demonstrating the applicability of our approach, we re-prove Lamport et al.’s well-known solution to the Byzantine Generals Problem [16] with four parties. We further complete a result of Achenbach et al. [1], proving that a “firewall combiner” for three network firewalls is available.