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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, 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 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: Is asynchronous parallel composition even a realistic goal? 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.
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CostCO: An automatic cost modeling framework for secure multi-party computation
The last decade has seen an explosion in the number of new secure multi-party computation (MPC) protocols that enable collaborative computation on sensitive data. No single MPC protocol is optimal for all types of computation. As a result, researchers have created hybrid-protocol compilers that translate a program into a hybrid protocol that mixes different MPC protocols. Hybrid-protocol compilers crucially rely on accurate cost models, which are handwritten by the compilers' developers, to choose the correct schedule of protocols. In this paper, we propose CostCO, the first automatic MPC cost modeling framework. CostCO develops a novel API to interface with a variety of MPC protocols, and leverages domain-specific properties of MPC in order to enable efficient and automatic cost-model generation for a wide range of MPC protocols. CostCO employs a two-phase experiment design to efficiently synthesize cost models of the MPC protocol's runtime as well as its memory and network usage. We verify CostCO's modeling accuracy for several full circuits, characterize the engineering effort required to port existing MPC protocols, and demonstrate how hybrid-protocol compilers can leverage CostCO's cost models.
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- Award ID(s):
- 1730628
- PAR ID:
- 10399374
- Date Published:
- Journal Name:
- 2022 IEEE 7th European Symposium on Security and Privacy (EuroS&P)
- Page Range / eLocation ID:
- 140 to 153
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/EuroSP53844.2022.00017
