Is the JCJ voting system really coercion-resistant?

Coercion-resistance is a security property of electronic voting, often considered as a must-have for high-stake elections. The JCJ voting scheme, proposed in 2005, is still the reference when designing a coercion-resistant protocol. We highlight a weakness in JCJ that is also present in all the systems following its general structure. It comes from the procedure that precedes the tally, where the trustees remove the ballots that should not be counted. This phase leaks more information than necessary, leading to potential threats for the coerced voters. Fixing this leads to the notion of cleansing-hiding, that we apply to form a variant of JCJ that we call CHide

Public Evidence from Secret Ballots

Elections seem simple---aren't they just counting? But they have a unique, challenging combination of security and privacy requirements. The stakes are high; the context is adversarial; the electorate needs to be convinced that the results are correct; and the secrecy of the ballot must be ensured. And they have practical constraints: time is of the essence, and voting systems need to be affordable and maintainable, and usable by voters, election officials, and pollworkers. It is thus not surprising that voting is a rich research area spanning theory, applied cryptography, practical systems analysis, usable security, and statistics. Election integrity involves two key concepts: convincing evidence that outcomes are correct and privacy, which amounts to convincing assurance that there is no evidence about how any given person voted. These are obviously in tension. We examine how current systems walk this tightrope.Comment: To appear in E-Vote-Id '1

Scalable Coercion-Resistant E-Voting under Weaker Trust Assumptions

Electronic voting (e-voting) is regularly used in many countries and organizations for legally binding elections. In order to conduct such elections securely, numerous e-voting systems have been proposed over the last few decades. Notably, some of these systems were designed to provide coercion-resistance. This property protects against potential adversaries trying to swing an election by coercing voters. Despite the multitude of existing coercion-resistant e-voting systems, to date, only few of them can handle large-scale Internet elections efficiently. One of these systems, VoteAgain (USENIX Security 2020), was originally claimed secure under similar trust assumptions to state-of-the-art e-voting systems without coercion-resistance. In this work, we review VoteAgain's security properties. We discover that, unlike originally claimed, VoteAgain is no more secure than a trivial voting system with a completely trusted election authority. In order to mitigate this issue, we propose a variant of VoteAgain which effectively mitigates trust on the election authorities and, at the same time, preserves VoteAgain's usability and efficiency. Altogether, our findings bring the state of science one step closer to the goal of scalable coercion-resistant e-voting being secure under reasonable trust assumptions

What proof do we prefer? Variants of verifiability in voting

In this paper, we discuss one particular feature of Internet voting, verifiability, against the background of scientific literature and experiments in the Netherlands. In order to conceptually clarify what verifiability is about, we distinguish classical verifiability from constructive veriability in both individual and universal verification. In classical individual verifiability, a proof that a vote has been counted can be given without revealing the vote. In constructive individual verifiability, a proof is only accepted if the witness (i.e. the vote) can be reconstructed. Analogous concepts are de- fined for universal veriability of the tally. The RIES system used in the Netherlands establishes constructive individual verifiability and constructive universal verifiability, whereas many advanced cryptographic systems described in the scientific literature establish classical individual verifiability and classical universal verifiability. If systems with a particular kind of verifiability continue to be used successfully in practice, this may influence the way in which people are involved in elections, and their image of democracy. Thus, the choice for a particular kind of verifiability in an experiment may have political consequences. We recommend making a well-informed democratic choice for the way in which both individual and universal verifiability should be realised in Internet voting, in order to avoid these unconscious political side-effects of the technology used. The safest choice in this respect, which maintains most properties of current elections, is classical individual verifiability combined with constructive universal verifiability. We would like to encourage discussion about the feasibility of this direction in scientific research

Accuracy: The fundamental requirement for voting systems

There have been several attempts to develop a comprehensive account of the requirements for voting systems, particularly for public elections. Typically, these approaches identify a number of "high level" principals which are then refined either into more detailed statements or more formal constructs. Unfortunately, these approaches do not acknowledge the complexity and diversity of the contexts in which voting takes place. This paper takes a different approach by arguing that the only requirement for a voting system is that it is accurate. More detailed requirements can then be derived from this high level requirement for the particular context in which the system is implemented and deployed. A general, formal high level model for voting systems and their context is proposed. Several related definitions of accuracy for voting systems are then developed, illustrating how the term "accuracy" is in interpreted in different contexts. Finally, a context based requirement for voting system privacy is investigated as an example of deriving a subsidiary requirement from the high level requirement for accuracy

HandiVote: simple, anonymous, and auditable electronic voting

We suggest a set of procedures utilising a range of technologies by which a major democratic deficit of modern society can be addressed. The mechanism, whilst it makes limited use of cryptographic techniques in the background, is based around objects and procedures with which voters are currently familiar. We believe that this holds considerable potential for the extension of democratic participation and control

An Epistemic Approach to Coercion-Resistance for Electronic Voting Protocols

Coercion resistance is an important and one of the most intricate security requirements of electronic voting protocols. Several definitions of coercion resistance have been proposed in the literature, including definitions based on symbolic models. However, existing definitions in such models are rather restricted in their scope and quite complex. In this paper, we therefore propose a new definition of coercion resistance in a symbolic setting, based on an epistemic approach. Our definition is relatively simple and intuitive. It allows for a fine-grained formulation of coercion resistance and can be stated independently of a specific, symbolic protocol and adversary model. As a proof of concept, we apply our definition to three voting protocols. In particular, we carry out the first rigorous analysis of the recently proposed Civitas system. We precisely identify those conditions under which this system guarantees coercion resistance or fails to be coercion resistant. We also analyze protocols proposed by Lee et al. and Okamoto.Comment: An extended version of a paper from IEEE Symposium on Security and Privacy (S&P) 200