Simplified Universal Composability Framework

We introduce a simplified universally composable (UC) security framework in our thesis (2005). In this paper we present an updated more comprehensive and illustrated version. The introduction of our simplified model is motivated by the difficulty to describe and analyze concrete protocols in the full UC framework due to its generality and complexity.The main differences between our formalization and the general UC security framework are that we consider: a fixed number of parties, static corruption, and simple ways to bound the running times of the adversary and environment. However, the model is easy to extend to adaptive adversaries. Authenticated channels become a trivial ideal functionality.We generalize the framework to allow protocols to securely realize other protocols. This allows a natural and modular description and analysis of protocols.We introduce invertible transforms of models that allow us to reduce the proof of the composition theorem to a simple special case and transform any hybrid protocol into a hybrid protocol with at most one ideal functionality. This factors out almost all of the technical details of our framework to be considered when relating our framework to any other security framework, e.g., the UC framework, and makes this easy.