key: 2011-attacking-ballot-secrecy-in-Helios
type: inproceedings
title: "Attacking and fixing Helios: An analysis of ballot secrecy"
authors:
  - Véronique Cortier
  - Ben Smyth
year: 2011
month: 6
booktitle: "CSF'11: 24th Computer Security Foundations Symposium"
pages: 297--311
publisher: IEEE Computer Society
doi: 10.1109/CSF.2011.27
description: >-
  This paper presents attacks against the Helios electronic voting protocol that violate ballot
  secrecy.
keywords: >-
  attack, vulnerability, exploit, Helios, electronic voting, ballot independence, ballot secrecy,
  malleability, privacy, end-to-end verifiable
abstract: >-
  Helios 2.0 is an open-source web-based end-to-end verifiable electronic voting system, suitable
  for use in low-coercion environments. In this paper, we analyse ballot secrecy and discover a
  vulnerability which allows an adversary to compromise the privacy of voters. This vulnerability
  has been successfully exploited to break privacy in a mock election using the current Helios
  implementation. Moreover, the feasibility of an attack is considered in the context of French
  legislative elections and, based upon our findings, we believe it constitutes a real threat to
  ballot secrecy in such settings. Finally, we present a fix and show that our solution satisfies a
  formal definition of ballot secrecy using the applied pi calculus.
video:
  youtube: fWvl9uJgpc0
  text: Video demonstration
extra: >
  <h2>Video demonstration</h2>

  <p>A video demonstrating this attack is available on <a
  href="http://www.youtube.com/watch?v=fWvl9uJgpc0">YouTube</a>.</p>
supersededby:
  - key: 2012-attacking-ballot-secrecy-in-Helios
    text: journal version
links:
  - file: Smyth11-attacking-Helios.IEEE.pdf
    text: Conference paper
  - file: Smyth10-attacking-Helios.pdf
    text: Technical Report
    alt:
      url: http://eprint.iacr.org/2010/625
      text: Cryptology ePrint Archive version
  - url: https://doi.org/10.1109/CSF.2011.27
    text: Official version