Due to resource-saving and efficiency consideration, electronic voting (e-voting) gradually replaces traditional paper-based voting in some developed countries. An anonymous e-voting system that can be used in elections with large electorates must meet various security requirements, such as anonymity, uncoercibility, tally correctness, unrecastability, verifiability, and so on. Especially, the uncoercibility property is an essential property which can greatly reduce the possibility of coercion and bribe. Since each voter can obtain one and only one voting receipt in an electronic voting system, coercers or bribers can enforce legal voters to show their voting receipts to identify whether the enforced voters follow their will or not. It turns out that the coercion and bribe will succeed more easily in digital environments than that in traditional paper-based voting. In this dissertation, we analyze four possible scenarios leading to coercion and discover that the randomization property is necessary to blind-signature-based e-voting systems against coercion. Based on this result, we extend our research and come up with two provably secure randomized blind signature schemes from different cryptographic primitives, which can be adopted as key techniques for an electronic voting system against coercion and bribery.

Due to convenience and efficiency, electronic voting (e-voting) techniques gradually replace traditional paper-based voting activities in some developed countries. A secure anonymous e-voting system has to satisfy many properties, such as completeness, tally correctness, and uncoercibility, where the uncoercibility property is the most difficult one to be achieved. Since each voter can obtain a voting receipt in an electronic voting system, coercion and bribe (vote-buying and vote-selling are included) become more and more serious in electronic voting environments than traditional paper-based voting environments. Unfortunately, most of the solutions, like receipt-freeness or untappable channels, proposed in the literature, are impractical owing to lack of efficiency or too complicated to be implemented. It will make uncoercible e-voting systems unacceptable by the people. In order to cope with the drawbacks of the previous schemes, this thesis will present a generic idea, which is independent of the underlying cryptographic components, on electronic voting to achieve the uncoercibility property and other requirements. The proposed method is an efficient and quite practical solution to match the current environments of electronic voting.