Improved Coercion-Resistant Electronic Elections through Deniable Re-Voting

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Presented at Jets 2015 by

Dirk Achenbach

Jörn Müller-quade

Carmen Kempka

Bernhard Löwe

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.