Attacking and fixing Helios: An analysis of ballot secrecy

Véronique Cortier (1) , Ben Smyth

1 CASSIS - Combination of approaches to the security of infinite states systems

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.

Domaines: Cryptographie et sécurité [cs.CR]

Véronique Cortier, Ben Smyth. Attacking and fixing Helios: An analysis of ballot secrecy. 24th IEEE Computer Security Foundations Symposium (CSF'11), Jun 2011, Cernay-la-Ville, France. pp.297 - 311, ⟨10.1109/CSF.2011.27⟩. ⟨inria-00638556⟩