Measuring Voter-Controlled Privacy

In voting, the notion of receipt-freeness has been proposed to express that a voter cannot gain any information to prove that she has voted in a certain way. It aims to prevent vote buying, even when a voter chooses to renounce her privacy. In this paper, the authors distinguish various ways that a voter can communicate with the intruder to reduce her privacy and classify these according to their ability to reduce the privacy of a voter. They develop a framework combining knowledge reasoning and trace equivalences to formally model voting protocols and define vote privacy for the voters. Their framework is quantitative, in the sense that it defines a measure for the privacy of a voter.