Two models of efficient mixnet-based receipt-free voting using (threshold) re-encryption
Receipt-freeness is an enhanced notion of privacy required to prevent vote buying, selling or coercion. It is an essential security property, such that the voting result accurately reflects true opinions of the voters. We propose two models of efficient mixnet-based voting schemes providing receipt-freeness in continuing the work by Lee et al. Efficiency is obtained by employing an optimistic mixnet, a modification of the mix-network scheme by Golle et al. The first model employs a trusted administrator to provide a re-encryption service, and assumes that a two-way untappable channel is used between the voters and the administrator. The second model provides a stronger notion of receipt-freeness by employing multiple administrators providing threshold re-encryption service. Use of the quorum of administrators lowers the trust required on a single administrator to perform the re-encryption service, and also offers more robustness in the protocol. Voters verify the correctness of the randomization process by checking designated verifier re-encryption proofs from the administrator. A batch verification technique is employed such that checking of the proofs in the second model is still efficient.
receipt-freeness threshold re-encryption randomization batch verification secure electronic voting designated-verifier re-encryption proof