Paper 2022/760

Privacy Preserving Opinion Aggregation

Abstract

There are numerous settings in which people’s preferences are aggregated outside of formal elections, and where privacy and verification are important but the stringent coercion-resistant properties of government elections do not apply, a prime example being social media platforms. In contrast to the centrally organised, single-shot elections on which most of the literature is focused, our settings of interest often have no trusted authority and are iterative, i.e., publish partial tallies before all votes are received. In this work, we explore opinion aggregation in a decentralised, iterative setting. In our novel protocol,randomly-chosen parties take turns to decrypt aggregated votes in an incentive-driven manner. Our simple construction leverages homomorphic encryption and secret sharing in a novel manner to provide security of the tally, public and individual verifiability, as well as vote privacy and liveness guarantees. Contrary to existing voting schemes, our protocol is ideal for the iterative setting.