Abstract
Sybil attacks, in which fake or duplicate identities
(sybils) infiltrate an online community, pose a serious threat to such communities, as they might tilt
community-wide decisions in their favor. While the
extensive research on sybil identification may help
keep the fraction of sybils in such communities low,
it cannot however ensure their complete eradication. Thus, our goal is to enhance social choice
theory with effective group decision mechanisms
for communities with bounded sybil penetration.
Inspired by Reality-Aware Social Choice [Shapiro
and Talmon, 2018], we use the status quo as the
anchor of sybil resilience, characterized by sybil
safety – the inability of sybils to change the status quo against the will of the genuine agents, and
sybil liveness – the ability of the genuine agents to
change the status quo against the will of the sybils.
We consider the social choice settings of deciding
on a single proposal, on multiple proposals, and on
updating a parameter. For each, we present social
choice rules that are sybil-safe and, under certain
conditions, satisfy sybil-liveness