Universal Composability is Robust Compilation

This paper discusses the relationship between two frameworks: universal composability (UC) and robust compilation (RC). In cryptography, UC is a framework for the specification and analysis of cryptographic protocols with a strong compositionality guarantee: UC protocols remain secure even when composed with other protocols. In programming language security, RC is a novel framework for determining secure compilation by proving whether compiled programs are as secure as their source-level counterparts no matter what target-level code they interact with. Presently, these disciplines are studied in isolation, though we argue that there is a deep connection between them and exploring this connection will benefit both research fields. This paper formally proves the connection between UC and RC and then it explores the benefits of this connection (focussing on perfect, rather than computational UC). For this, this paper first identifies which conditions must programming languages fulfil in order to possibly attain UC-like composition. Then, it proves UC of both an existing and a new commitment protocol as a corollary of the related compilers attaining RC. Finally, it mechanises these proofs in Deepsec, obtaining symbolic guarantees that the protocol is indeed UC. Our connection lays the groundwork towards a better and deeper understanding of both UC and RC, and the benefits we showcase from this connection provide evidence of scalable mechanised proofs for UC. In order to differentiate various sub-parts of the UC and RC frameworks, we use syntax highlighting to a degree that colourblind and black&white readers can benefit from [78]. UC talks about ideal functionalities (typeset in a verbatim, emerald font) and protocol implementations (typeset in a sans-serif, orange font). RC deals with source languages (typeset in an italics, blue font) and target ones (typeset in a bold, red font). Elements that are common to each framework are typeset in a black, sans-serif font for UC and in a black, italicised font for RC to avoid repetition. For a better experience, please view this paper in colour.