Ge, HuangyiChau, Sze YiuGonsalves, Victor E.Liu, HuianWang, TianhaoZou, XukaiLi, Ninghui2020-11-062020-11-062019Ge, H., Chau, S. Y., Gonsalves, V. E., Li, H., Wang, T., Zou, X., & Li, N. (2019). Koinonia: Verifiable e-voting with long-term privacy. Proceedings of the 35th Annual Computer Security Applications Conference, 270–285. https://doi.org/10.1145/3359789.3359804https://hdl.handle.net/1805/24283Despite years of research, many existing e-voting systems do not adequately protect voting privacy. In most cases, such systems only achieve "immediate privacy", that is, they only protect voting privacy against today's adversaries, but not against a future adversary, who may possess better attack technologies like new cryptanalysis algorithms and/or quantum computers. Previous attempts at providing long-term voting privacy (dubbed "everlasting privacy" in the literature) often require additional trusts in parties that do not need to be trusted for immediate privacy. In this paper, we present a framework of adversary models regarding e-voting systems, and analyze possible threats to voting privacy under each model. Based on our analysis, we argue that secret-sharing based voting protocols offer a more natural and elegant privacy-preserving solution than their encryption-based counterparts. We thus design and implement Koinonia, a voting system that provides long-term privacy against powerful adversaries and enables anyone to verify that each ballot is well-formed and the tallying is done correctly. Our experiments show that Koinonia protects voting privacy with a reasonable performance.enPublisher Policyprivacye-votingvoting privacyConference proceedings