Optimal Synchronous Approximate Agreement with Asynchronous Fallback

Abstract

Approximate Agreement (AA) allows a set of n parties that start with real-valued inputs to obtain values that are at most within a parameter > 0 from each other and within the range of their inputs. Existing AA protocols, both for the synchronous network model (where any message is delivered within a known delay Δtime) and the asynchronous network model, are secure when up to t