Cryptographic Voting Protocols

Cryptographic Voting Protocols

Kannan Balasubramanian (Mepco Schlenk Engineering College, India) and Jayanthi Mathanan (Mepco Schlenk Engineering College, India)
DOI: 10.4018/978-1-5225-2915-6.ch010
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Abstract

Most of the voting protocols proposed so far can be categorized into two main types based on the approach taken: schemes using blind signatures and schemes using homomorphic encryption. In the schemes using blind signatures, the voter initially obtains a token – a blindly signed message unknown to anyone except himself. In the schemes using homomorphic encryption the voter cooperates with the authorities in order to construct an encryption of his vote. Due to the homomorphic property, an encryption of the sum of the votes is obtained by multiplying the encrypted votes of all voters. This chapter reviews schemes based on blind signatures and homomorphic encryption and proposes improvements to the existing schemes.
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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.

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