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

One of the cryptographers might be paying for the

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Unformatted text preview: Bob knows b, and together they will determine whether a = b, such that Bob does not learn anything additional about a and Alice does not learn anything additional about b. Details are in Section 23.14. Protocol #4 This is another problem for secure multiparty computation [1373]: A council of seven meets regularly to cast secret ballots on certain issues. (All right, they rule the world—don’t tell anyone I told you.) All council members can vote yes or no. In addition, two parties have the option of casting “super votes”: S-yes and S-no. They do not have to cast super votes; they can cast regular votes if they prefer. If no one casts any super votes, then the majority of votes decides the issue. In the case of a single or two equivalent super votes, all regular votes are ignored. In the case of two contradicting super votes, the majority of regular votes decides. We want a protocol that securely performs this style of voting. Two examples should illustrate the voting process. Assume there are five regular voters, N1 through N5, and two super voters: S1 and S2. Here’s the vote on issue #1: S1 S-yes S2 no N1 no N2 no N3 no N4 yes N5 yes In this instance the only vote that matters is S1 ’s, and the result is “yes.” Here is the vote on issue #2: S1 S-yes S2 S-no N1 no N2 no N3 no N4 N5 yes yes Here the two super votes cancel and the majority of regular “no” votes decide the issue. If it isn’t important to hide the knowledge of whether the super vote or the regular vote was the deciding vote, this is an easy application of a secure voting protocol. Hiding that knowledge requires a more complicated secure multiparty computation protocol. This kind of voting could occur in real life. It could be part of a corporation’s organizational structure, where certain people have more power than others, or it could be part of the United Nations’s procedures, where certain nations have more power than others. Multiparty Unconditionally Secure Protocols This is just a simple case of a general theorem: Any function of n input...
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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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