Cryptographic Voting Protocols

Formulation Of The Voting Problem

A voting scheme must ensure not only that the voter can keep his vote private, but also that he must keep it private. In other words, the voter should not be able to prove to the third party that he has cast a particular vote. He must not be able to construct a receipt proving the content of his vote. This property is referred to as receipt-freeness.

Only a few schemes guaranteeing receipt-freeness have been proposed. Known receipt-free scheme using blind signatures (Okamoto, 1997), assumes the existence of a special anonymous untappable channel. Achieving both secure and anonymous communication would, however, be extremely difficult. As for the schemes using homomorphic encryption, some efficient receipt-free schemes have already been proposed. Only the scheme proposed by Hirt and Sako (Hirt et al., 2000).

The Voting committee takes count of the voters: It allows only eligible voters to vote, and it ensures that every voter votes at most once. After the elections, the voting committee counts the votes and publishes the result. The votes remain secret. No one should not be able to say how anyone has voted. Even if the person says how he has voted, we cannot believe him, since he can lie. On the other hand, a person casting his vote cannot be absolutely sure that his vote was really counted. Everyone has to believe that the voting committee is honest and it would not disrupt the elections.