Claudia Z. Acemyan, Philip Kortum, Michael D. Byrne, and Dan S. Wallach, Rice University The aim of this paper is to identify user errors, and the related potential design deficiencies, that contributed to participants failing to vote cast and vote verify across three end-to-end voting systems: Helios, Prêt à Voter, and Scantegrity II. To understand why voters could not cast a vote 42% of the time and verify that their ballots were cast and counted with the tested e2e systems 53% of the time, we reviewed data collected during a system usability study. An analysis of the findings revealed subjects were most often not able to vote with Helios because they did not log in after encrypting their ballot but before casting it. For both Prêt à Voter and Scantegrity II, failing to vote was most frequently attributed to not scanning the completed ballot. Across all three systems, the most common reason participants did not verify their vote was due to not casting a ballot in the first place. The aim of this paper is to identify user errors, and the related potential design deficiencies, that contributed to participants failing to vote cast and vote verify across three end-to-end voting systems: Helios, Prêt à Voter, and Scantegrity II. To understand why voters could not cast a vote 42% of the time and verify that their ballots were cast and counted with the tested e2e systems 53% of the time, we reviewed data collected during a system usability study. An analysis of the findings revealed subjects were most often not able to vote with Helios because they did not log in after encrypting their ballot but before casting it. For both Prêt à Voter and Scantegrity II, failing to vote was most frequently attributed to not scanning the completed ballot. Across all three systems, the most common reason participants did not verify their vote was due to not casting a ballot in the first place. While there were numerous usability failures identified in the study, these errors can likely be designed out of the systems. This formative information can be used to avoid making the same types of mistakes in the next generation of voting systems—ultimately resulting in more usable e2e methods.
Dirk Achenbach, Karlsruhe Institute of Technology; Carmen Kempka, NTT Secure Platform Laboratories; Bernhard Löwe and Jörn Müller-Quade, Karlsruhe Institute of Technology In a democracy, it is essential that voters cast their votes independently and freely, without any improper influence. Particularly, mechanisms must be put into place that prevent—or at least severely impede—the coercion of voters. One possible counter- measure to coercion is revoting: after casting a vote under coercion, the voter can re-cast and overwrite her choice. However, revoting is only meaningful as a strategy to evade coercion if the adversary cannot infer whether the voter has modified her choice—revoting needs to be deniable, while still being publicly verifiable. We define the notions of correctness, verifiability, and deniability for a tallying protocol which allows for revoting. We also present a protocol realizing these notions. To the best of our knowledge, our solution is the first to achieve both deniability and public verifiability without asking information about the voter’s previously-cast ballots for revoting. In a democracy, it is essential that voters cast their votes independently and freely, without any improper influence. Particularly, mechanisms must be put into place that prevent—or at least severely impede—the coercion of voters. One possible counter- measure to coercion is revoting: after casting a vote under coercion, the voter can re-cast and overwrite her choice. However, revoting is only meaningful as a strategy to evade coercion if the adversary cannot infer whether the voter has modified her choice—revoting needs to be deniable, while still being publicly verifiable. We define the notions of correctness, verifiability, and deniability for a tallying protocol which allows for revoting. We also present a protocol realizing these notions. To the best of our knowledge, our solution is the first to achieve both deniability and public verifiability without asking information about the voter’s previously-cast ballots for revoting. A seemingly competitive line of work, started by the well-known work of Juels, Catalano, and Jakobsson, uses fake credentials as a strategy to evade coercion: the voter presents to the adversary a fake secret for voting. In this work, we extend Juels et al.’s work to achieve deniable revoting. Their solution also allows for revoting, however not deniably. Our solution supports fake credentials as an opt-in property, providing the advantages of both worlds.
Alan Szepieniec and Bart Preneel, KU Leuven and iMinds This paper presents a novel unifying framework for electronic voting in the universal composability model that includes a property which is new to universal composability but well-known to voting systems: universal verifiability. Additionally, we propose three new techniques for secure electronic voting and prove their security and universal verifiability in the universal composability framework. 1. A tally-hiding voting system, in which the tally that is released consists of only the winner without the vote count. Our proposal builds on a novel solution to the millionaire problem which is of independent interest. 2. A self-tallying vote, in which the tally can be calculated by any observer as soon as the last vote has been cast — but before this happens, no information about the tally is leaked. 3. Authentication of voting credentials, which is a new approach for electronic voting systems based on anonymous credentials. This paper presents a novel unifying framework for electronic voting in the universal composability model that includes a property which is new to universal composability but well-known to voting systems: universal verifiability. Additionally, we propose three new techniques for secure electronic voting and prove their security and universal verifiability in the universal composability framework. 1. A tally-hiding voting system, in which the tally that is released consists of only the winner without the vote count. Our proposal builds on a novel solution to the millionaire problem which is of independent interest. 2. A self-tallying vote, in which the tally can be calculated by any observer as soon as the last vote has been cast — but before this happens, no information about the tally is leaked. 3. Authentication of voting credentials, which is a new approach for electronic voting systems based on anonymous credentials. In this approach, the vote authenticates the credential so that it cannot afterwards be used for any other purpose but to cast that vote. We propose a practical voting system that instantiates this high-level concept.
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