A Unified View on MPC with Dynamic Committees

Abstract Multi-Party Computation (MPC) enables a set of parties to jointly compute a function while preserving the privacy of their inputs. Although the problem has been studied for several decades, most prior work considers the classical setting in which the set of parties is fixed throughout the protocol execution. This assumption is poorly suited for modern applications that are long-lived and in which parties may join or leave the computation dynamically. Motivated by this limitation, a growing body of recent work has introduced models of MPC with dynamic committees, including YOSO MPC, Fluid MPC, Layered MPC, and SCALES, among others. The proliferation of such models raises natural questions: how do these approaches relate to each other, and can they be unified under a common framework? We show that MPC with dynamic committees can be reduced to the design of a classical MPC protocol with a static set of parties and a general adversary structure, but where the interaction pattern is constrained to follow a fixed layered acyclic graph. Each party corresponds to a node in the graph and can send secret messages along its outgoing edges. We further demonstrate that existing dynamic-committee MPC models can be recovered as specific instantiations of this layered-graph framework.