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Experiments with Universal Composability in EasyCrypt

This repository contains experiments in formalizing Universally Composable (UC) Security using the EasyCrypt proof assistant. This is joint work between researchers

with the assistance of

In our architecture, functionalities (real protocols, or ideal functionalities) have hierarchical addresses, and we build abstractions that route messages to their destinations, modeling the coroutine-style communication of UC.

Secure Message Communication

In our first full example, we formalized the proof of the UC security of secure message communication using a one-time pad that's agreed using Diffie-Hellman key exchange. Our goal in this example was to test our EasyCrypt UC architecture, illustrating how instances of UC's composition operation and theorem may be formalized in EasyCrypt.

This work is described in the extended version of the CSF 2019 paper, EasyUC: Using EasyCrypt to Mechanize Proofs of Universally Composable Security.

UC Domain Specific Language

We have designed and implemented a parser, typechecker and interpreter for a domain specific language (DSL) for expressing functionalities (protocols and ideal functionalities) and simulators. The DSL will allow crypto theorists to easily write and understand functionalities and simulators. Its design was driven by the expression of functionalities and simulators in our EasyCrypt architecture for UC. But it allows expression at a much higher level, avoiding all the message-routing boilerplate. DSL type-checking prevents errors like badly formed messages (e.g., ones with bad source addresses), simulators that interfere with communication between environment and adversary, or violations of the coroutine model (trying to send two message in sequence, without control having first returned). We are working toward a translator from the DSL into EasyCrypt, where the sequence of games security proofs will be mechanized.