CryptoDB
Is It Even Possible? On the Parallel Composition of Asynchronous MPC Protocols
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| Conference: | TCC 2025 |
| Abstract: | Despite several known idiosyncrasies separating the synchronous and the asynchronous models, asynchronous secure multi-party computation (MPC) protocols demonstrate high-level similarities to synchronous MPC, both in design philosophy and abstract structure. As such, a coveted, albeit elusive, {\em desideratum} is to devise automatic translators (e.g., protocol compilers) of feasibility and efficiency results from one model to the other. In this work, we demonstrate new challenges associated with this goal. Specifically, we study the case of \emph{parallel composition} in the asynchronous setting. We provide formal definitions of this composition operation in the UC framework, which, somewhat surprisingly, have been missing from the literature. Using these definitions, we then turn to charting the feasibility landscape of asynchronous parallel composition. We first prove strong impossibility results for composition operators that do not assume knowledge of the functions and/or the protocols that are being composed. These results draw a grim feasibility picture, which is in sharp contrast with the synchronous model, and highlight the question: \begin{center} {\em Is asynchronous parallel composition even a realistic goal?} \end{center} To answer the above (in the affirmative), we provide conditions on the composed protocols that enable a useful form of asynchronous parallel composition, as it turns out to be common in existing constructions. |
BibTeX
@inproceedings{tcc-2025-36200,
title={Is It Even Possible? On the Parallel Composition of Asynchronous MPC Protocols},
publisher={Springer-Verlag},
author={Ran Cohen and Pouyan Forghani and Juan Garay and Rutvik Patel and Vassilis Zikas},
year=2025
}