Election Verifiability or Ballot Privacy: Do We Need to Choose?

Abstract

Abstract. We propose a new encryption primitive, commitment consistent encryption (CCE), and instances of this primitive that enable building the first universally verifiable voting schemes with a perfectly private audit trail (PPAT) and practical complexity. That is:-the audit trail that is published for verifying elections guarantees everlasting privacy, and -the computational load required from the participants is only increased by a small constant factor compared to traditional voting schemes, and is optimal in the sense of Cramer, Gennaro and Schoenmakers [16]. These properties make it possible to introduce election verifiability in large scale elections as a pure benefit, that is, without loss of privacy compared to a non-verifiable scheme and at a similar level of efficiency. We propose different approaches for constructing voting schemes with PPAT from CCE, as well as two efficient CCE constructions: one is tailored for elections with a small number of candidates, while the second is suitable for elections with complex ballots.

SoK: A Comprehensive Analysis of Game-Based Ballot Privacy Definitions

“…Game-based privacy [23], [24], [25], [12], [18], [19], [26], [22], [20], [21] (our terminology) definitions require that it should be hard for an adversary to win a game with a challenger behaving in a fully specified manner, in the spirit of traditional indistinguishability definitions for encryption. In this section we review the most relevant ballot privacy definitions in the literature.…”

“…Recently, Cuvelier, Pereira and Peters [26] proposed a variant of the BPRIV1 setting/definition to capture ballot privacy even in the presence of computationally unbounded adversaries, and which is named perfectly private audit trail (PPAT). Similarly to BPRIV1, the definition PPAT is limited in the sense that an adversary is not allowed to see the auxiliary data Π.…”

“…• too limited [23], [24], [25], [12], [11], [17], [26]: while we did not identify any flaw in these definitions, they restrict the class of protocols or privacy breaches that can be considered. For example, they may lead to inconsistent results when applied to protocols that use some natural result functions (e.g., the majority function) or may not be applicable to protocols that output not only a result but also a proof of correct tallying (such as most cryptographic protocols do), or they may only detect specific privacy breaches (e.g.…”

El Voto Electrónico Y Retos Criptográficos Relacionados

“…Privacidad eterna del voto (Moran & Naor, 2010;Demirel, Graaf & Araújo, 2012;Buchmann, Demirel & van de Graaf, 2013;Cuvelier, Pereira & Peters, 2013).…”

Practical Everlasting Privacy

“…These systems have computational verifiability instead of perfect verifiability, and are considered less usable and computationally more expensive than systems relying on encryptions. More recently, schemes have been proposed with a weaker form of everlasting privacy (e.g., [10,12]); they rely on encryptions for counting votes, but use commitments rather than encryptions for verifiability purposes. Thus, the bulletin board which only publishes the commitments does not weaken the privacy provided by the underlying scheme.…”