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Machine-checked proofs for electronic voting: Privacy and verifiability for belenios

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Original languageEnglish
Title of host publication2018 IEEE 31st Computer Security Foundations Symposium (CSF 2018)
Subtitle of host publicationProceedings of a meeting held 9-12 July 2018, Oxford, United Kingdom
Publisher or commissioning bodyInstitute of Electrical and Electronics Engineers (IEEE)
Number of pages15
ISBN (Electronic)9781538666807
ISBN (Print)9781538666814
DateAccepted/In press - 31 Mar 2018
DateE-pub ahead of print - 7 Aug 2018
DatePublished (current) - Sep 2018
Event31st IEEE Computer Security Foundations Symposium, CSF 2018 - Oxford, United Kingdom
Duration: 9 Jul 201812 Jul 2018

Publication series

ISSN (Print)2374-8303


Conference31st IEEE Computer Security Foundations Symposium, CSF 2018
CountryUnited Kingdom


We present a machine-checked security analysis of Belenios - a deployed voting protocol used already in more than 200 elections. Belenios extends Helios with an explicit registration authority to obtain eligibility guarantees. We offer two main results. First, we build upon a recent framework for proving ballot privacy in EasyCrypt. Inspired by our application to Belenios, we adapt and extend the privacy security notions to account for protocols that include a registration phase. Our analysis identifies a trust assumption which is missing in the existing (pen and paper) analysis of Belenios: Ballot privacy does not hold if the registrar misbehaves, even if the role of the registrar is seemingly to provide eligibility guarantees. Second, we develop a novel framework for proving strong verifiability in EasyCrypt and apply it to Belenios. In the process, we clarify several aspects of the pen-and-paper proof, such as how to deal with revote policies. Together, our results yield the first machine-checked analysis of both ballot privacy and verifiability properties for a deployed electronic voting protocol. Perhaps more importantly, we identify several issues regarding the applicability of existing definitions of privacy and verifiability to systems other than Helios. While we show how to adapt the definitions to the particular case of Belenios, our findings indicate the need for more general security notions for electronic voting protocols with registration authorities.

    Research areas

  • Easycrypt, electronic-voting, machine-checked-proofs, privacy, verifiability


31st IEEE Computer Security Foundations Symposium, CSF 2018

Duration9 Jul 201812 Jul 2018
CountryUnited Kingdom

Event: Conference



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