The Privacy And Verifiability of Voting Systems: Measures and Limits Open Access
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This dissertation presents an information-theoretic model of a vote counting system, and well-defined criteria for evaluating such a system with respect to integrity, privacy and verifiability. The impossibility of achieving perfect integrity, perfect verifiability and perfect privacy follows easily from the information-theoretic approach. The model is applied to the measurement of privacy loss in the ThreeBallot and Farnel voting systems, and finds both systems to have similar privacy loss. The consequences to voter privacy of three methods of auditing the mixnet-like primitives used in voter verifiable voting systems are analyzed using the model; the three audit procedures are found to impact privacy differently, and a previously unknown impact on privacy of one audit procedure is detailed. An attack that exploits this vulnerability to guess the contents of voters' ballots is implemented. The impact on election integrity of two vote-buying attacks is analyzed.