An election is a process through which citizens in liberal democracies select their governing bodies, usually through voting. For elections to be truly honest, people must be able to vote freely without being subject to coercion; that is why voting is usually done in a private manner. In this paper we analyze the security offered by a paper-ballot voting system that is used in Israel, as well as in several other countries around the world. we provide an algorithm which, based on publicly available information, breaks the privacy of the voters participating in such elections. Simulations based on real data collected in Israel show that our algorithm performs well, and can correctly recover the vote of up to 96 of the voters.
Each ballot box in the Israeli voting system can be modeled as a certain kind of a mix, namely a timed-mix. In such a mix, a buffer of messages is mixed once in each time period. The set of voters in each polling station corresponds to the set of senders, while the set of parties contesting in an election corresponds to the set of receivers. There are various known attacks on mixes @cite_9 @cite_20 @cite_21 @cite_18 @cite_3 and we refer the interested reader to a recent survey @cite_15 .
@cite_18 @cite_9 @cite_21 @cite_3 @cite_15 @cite_20
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We report on the design and implementation of a new cryptographic voting system, designed to retain the "look and feel" of standard, paper-based voting used in our country Israel while enhancing security with end-to-end verifiability guaranteed by cryptographic voting. Our system is dual ballot and runs two voting processes in parallel: one is electronic while the other is paper-based and similar to the traditional process used in Israel. Consistency between the two processes is enforced by means of a new, specially-tailored paper ballot format. We examined the practicality and usability of our protocol through implementation and field testing in two elections: the first being a student council election with over 2000 voters, the second a political party's election for choosing their leader. We present our findings, some of which were extracted from a survey we conducted during the first election. Overall, voters trusted the system and found it comfortable to use. In 1992, Bartholdi, Tovey, and Trick opened the study of control attacks on elections-- attempts to improve the election outcome by such actions as adding deleting candidates or voters. That work has led to many results on how algorithms can be used to find attacks on elections and how complexity-theoretic hardness results can be used as shields against attacks. However, all the work in this line has assumed that the attacker employs just a single type of attack. In this paper, we model and study the case in which the attacker launches a multipronged (i.e., multimode) attack. We do so to more realistically capture the richness of real-life settings. For example, an attacker might simultaneously try to suppress some voters, attract new voters into the election, and introduce a spoiler candidate. Our model provides a unified framework for such varied attacks. By constructing polynomialtime multiprong attack algorithms we prove that for various election systems even such concerted, flexible attacks can be perfectly planned in deterministic polynomial time. In computational social choice, one important problem is to take the votes of a subelectorate (subset of the voters), and summarize them using a small number of bits. This needs to be done in such a way that, if all that we know is the summary, as well as the votes of voters outside the subelectorate, we can conclude which of the m alternatives wins. This corresponds to the notion of compilation complexity, the minimum number of bits required to summarize the votes for a particular rule, which was introduced by [IJCAI-09]. We study three different types of compilation complexity. The first, studied by , depends on the size of the subelectorate but not on the size of the complement (the voters outside the subelectorate). The second depends on the size of the complement but not on the size of the subelectorate. The third depends on both. We first investigate the relations among the three types of compilation complexity. Then, we give upper and lower bounds on all three types of compilation complexity for the most prominent voting rules. We show that for l-approval (when l ≤ m 2), Borda, and Bucklin, the bounds for all three types are asymptotically tight, up to a multiplicative constant; for l-approval (when l > m 2), plurality with runoff, all Condorcet consistent rules that are based on unweighted majority graphs (including Copeland and voting trees), and all Condorcet consistent rules that are based on the order of pairwise elections (including ranked pairs and maximin), the bounds for all three types are asymptotically tight up to a multiplicative constant when the sizes of the subelectorate and its complement are both larger than m1+∊ for some ∊ > 0. Voting is a commonly applied method for the aggregation of the preferences of multiple agents into a joint decision. If preferences are binary, i.e., "yes" and "no", every voting system can be described by a (monotone) Boolean function @math . However, its naive encoding needs @math bits. The subclass of threshold functions, which is sufficient for homogeneous agents, allows a more succinct representation using @math weights and one threshold. For heterogeneous agents, one can represent @math as an intersection of @math threshold functions. Taylor and Zwicker have constructed a sequence of examples requiring @math and provided a construction guaranteeing @math . The magnitude of the worst-case situation was thought to be determined by in 2008, but the analysis unfortunately turned out to be wrong. Here we uncover a relation to coding theory that allows the determination of the minimum number @math for a subclass of voting systems. As an application, we give a construction for @math , i.e., there is no gain from a representation complexity point of view.