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Pret a Voter with Paillier Encryption

Lookup NU author(s): Professor Peter Ryan



The Pret a Voter schemes allow voters to confirm that their vote is accurately counted whilst maintaining ballot secrecy. An earlier version of Pret a Voter uses exponential ElGamal encryption enabling the use of re-encryption mixes in place of the decryption mixes. To render decryption tractable whilst avoiding the possibility of extreme values compromising ballot privacy, it was necessary to draw the seed values from a suitable statistical distribution, e.g., a binomial. In this paper we present a similar construction of the ballot forms but using Paillier encryption in place of ElGamal. The homomorphic properties of Paillier make it ideally suited to our construction and removes the need to constrain the distribution of seed values. As with the ElGamal version of the scheme, we have a distributed construction of encrypted ballot forms, though here we give an alternative construction that allows us to set an arbitrary collusion threshold for the leaking ballot information. This enables on-demand decryption and printing of the ballot forms and so eliminates the need to trust a single authority to keep this information secret and avoids chain of custody issues and chain voting style attacks. A number of further innovations are introduced, for example, providing the booth device with a share of the decryption key and transforming the receipt onions into a form directly decryptable in the booth, thus avoiding the need to have the tellers available during the voting period. This is a revised and extended version of TR 965.

Publication metadata

Author(s): Ryan PYA

Publication type: Report

Publication status: Published

Series Title: School of Computing Science Technical Report Series

Year: 2007

Pages: 30

Print publication date: 01/04/2007

Source Publication Date: April 2007

Report Number: 1014

Institution: School of Computing Science, University of Newcastle upon Tyne

Place Published: Newcastle upon Tyne