Electronic Voting: How Logic Can Help

Abstract

Electronic voting should offer at least the same guarantees than traditional paper-based voting systems. In order to achieve this, electronic voting protocols make use of cryptographic primitives, as in the more traditional case of authentication or key exchange protocols. All these protocols are notoriously difficult to design and flaws may be found years after their first release. Formal models, such as process algebra, Horn clauses, or constraint systems, have been successfully applied to automatically analyze traditional protocols and discover flaws. Electronic voting protocols however significantly increase the difficulty of the analysis task. Indeed, they involve for example new and sophisticated cryptographic primitives, new dedicated security properties, and new execution structures. After an introduction to electronic voting, we describe the current techniques for e-voting protocols analysis and review the key challenges towards a fully automated verification. 1 Context Electronic voting promises a convenient and efficient way for collecting and tallying votes, avoiding human counting errors. Several countries now use electronic voting for politically binding elections. This is for example the case of Argentina, United States, Norway, Canada, or France. However electronic voting also causes controversy. Indeed these systems have been shown to be vulnerable to attacks. For example, the Diebold machines as well as the electronic machines used in India have been attacked [44, 58]. Consequently, some countries like Germany, Netherlands, or the United Kingdom have stopped electronic voting, at least momentarily [47]. Electronic voting covers two distinct families of voting systems: voting machines and Internet voting. Voting machines are computers placed at polling stations. They provide an interface for the voters to cast their vote and they process the ballots. Internet voting do not need physical polling stations: voters may simply vote using their own device (computers, smartphones, etc.) from home. In this paper we focus on Internet voting. Internet voting raises several security challenges. Firstly, since votes need to be sent through the Internet, they obviously cannot be sent in clear. A simple solution would therefore to have all the voters encrypt their votes with the key of the voting server. At the end of the election, the server can then simply decrypt all the votes and announce the The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement no 258865, project ProSecure.

Alpha-Beta Privacy

“…There are many works on electronic voting using the applied pi-calculus or a similar calculus to model the protocol (see, e.g., [21,7,14,15,17,19] to name a few). The voting privacy goal is usually then expressed by the following trick: consider two processes that differ only in the concrete vote of two (honest) voters who swap their vote; then any such pair of processes must be indistinguishable.…”

Improving Automated Symbolic Analysis of Ballot Secrecy for E-Voting Protocols: A Method Based on Sufficient Conditions

“…Recently, new symbolic methods have been proposed [15]- [19] to analyse e-voting protocols. However, the applicability of these methods is still extremely limited both in the type of protocols that they can deal with and the type of security properties (including threat models) that they analyse (as acknowledged by [14], [17], [20]). The reasons for these limitations interact in a complex way with existing approaches.…”