Receipt-Free Electronic Voting Scheme with a Tamper-Resistant Randomizer

We investigate the receipt-freeness issue of electronic voting protocols. Receipt-freeness means that a voter neither obtains nor is able to construct a receipt proving the content of his vote. [Hirt01] proposed a receipt-free voting scheme by introducing a third-party randomizer and by using divertible zero-knowledge proof of validity and designatedverifier re-encryption proof. This scheme satisfies receipt-freeness under the assumption that the randomizer does not collude with a buyer and two-way untappable channel exists between voters and the randomizer. But untappable channel is hard to implement in real world and will cause inconvenience to voters although it is provided. In this paper we extend [Hirt01] such that a tamper-resistant randomizer (TRR), a secure hardware device such as smart card or Java card, replaces the role of third-party randomizer and untappable channel. Moreover K-out-of-L receipt-free voting is provided in more efficient manner by introducing divertible proof of difference.