Adapting Helios for provable ballot privacy

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Adapting Helios for provable ballot privacy (2011)

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by David Bernhard , Véronique Cortier , Olivier Pereira , Ben Smyth , Bogdan Warinschi

Venue:	In ESORICS’11: 16th European Symposium on Research in Computer Security, volume 6879 of LNCS
Citations:	16 - 8 self

BibTeX

@INPROCEEDINGS{Bernhard11adaptinghelios,
    author = {David Bernhard and Véronique Cortier and Olivier Pereira and Ben Smyth and Bogdan Warinschi},
    title = {Adapting Helios for provable ballot privacy},
    booktitle = {In ESORICS’11: 16th European Symposium on Research in Computer Security, volume 6879 of LNCS},
    year = {2011},
    pages = {335--354},
    publisher = {Springer}
}

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Abstract

Abstract. Recent results show that the current implementation of Helios, a practical e-voting protocol, does not ensure independence of the cast votes, and demonstrate the impact of this lack of independence on vote privacy. Some simple fixes seem to be available and security of the revised scheme has been studied with respect to symbolic models. In this paper we study the security of Helios using computational models. Our first contribution is a model for the property known as ballot privacy that generalizes and extends several existing ones. Using this model, we investigate an abstract voting scheme (of which the revised Helios is an instantiation) built from an arbitrary encryption scheme with certain functional properties. We prove, generically, that whenever this encryption scheme falls in the class of voting-friendly schemes that we define, the resulting voting scheme provably satisfies ballot privacy. We explain how our general result yields cryptographic security guarantees for the revised version of Helios (albeit from non-standard assumptions). Furthermore, we show (by giving two distinct constructions) that it is possible to construct voting-friendly encryption, and therefore voting schemes, using only standard cryptographic tools. We detail an instantiation based on ElGamal encryption and Fiat-Shamir non-interactive zero-knowledge proofs that closely resembles Helios and which provably satisfies ballot privacy. 1

Keyphrases

provable ballot privacy ballot privacy distinct construction elgamal encryption arbitrary encryption scheme standard cryptographic tool certain functional property encryption scheme voting scheme recent result voting-friendly encryption simple fix revised version abstract voting scheme fiat-shamir non-interactive zero-knowledge proof vote privacy current implementation computational model non-standard assumption voting-friendly scheme voting scheme provably satisfies symbolic model first contribution cast vote practical e-voting protocol

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