applied cryptography - protocols, algorithms, and source code in c

2 bob decrypts alices result with his private key he

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Unformatted text preview: d, the scrambling of the votes could be reversed by re-encrypting the emerging votes with the scrambler’s public key. As the protocol stands, the confidentiality of the votes is secure. Even more strongly, because of the initial random string, R1, even identical votes are encrypted differently at every step of the protocol. No one knows the outcome of the vote until step (11). What are the problems with this protocol? First, the protocol has an enormous amount of computation. The example described had only four voters and it was complicated. This would never work in a real election, with tens of thousands of voters. Second, Dave learns the results of the election before anyone else does. While he still can’t affect the outcome, this gives him some power that the others do not have. On the other hand, this is also true with centralized voting schemes. The third problem is that Alice can copy anyone else’s vote, even though she does not know what it is beforehand. To see why this could be a problem, consider a three-person election between Alice, Bob, and Eve. Eve doesn’t care about the result of the election, but she wants to know how Alice voted. So she copies Alice’s vote, and the result of the election is guaranteed to be equal to Alice’s vote. Other Voting Schemes Many complex secure election protocols have been proposed. They come in two basic flavors. There are mixing protocols, like “Voting without a Central Tabulating Facility, ” where everyone’s vote gets mixed up so that no one can associate a vote with a voter. There are also divided protocols, where individual votes are divided up among different tabulating facilities such that no single one of them can cheat the voters [360, 359, 118, 115]. These protocols only protect the privacy of voters to the extent that different “parts” of the government (or whoever is administering the voting) do not conspire against the voter. (This idea of breaking a central authority into different parts, who are only trusted when togeth...
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This note was uploaded on 10/18/2010 for the course MATH CS 301 taught by Professor Aliulger during the Fall '10 term at Koç University.

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