## (Universal) Unconditional Verifiability in E-Voting without Trusted Parties

Gina Gallegos-García, Vincenzo Iovino, Alfredo Rial, Peter B. Rønne, and Peter Y. A. Ryan. (Universal) Unconditional Verifiability in E-Voting without Trusted Parties. CoRR, abs/1610.06343, 2016.

### Abstract

In traditional e-voting protocols, privacy is often provided by a trusted authority that learns the votes and computes the tally. Some protocols replace the trusted authority by a set of authorities, and privacy is guaranteed if less than a threshold number of authorities are corrupt. For verifiability, stronger security guarantees are demanded. Typically, corrupt authorities that try to fake the result of the tally must always be detected. To provide verifiability, many e-voting protocols use Non-Interactive Zero-Knowledge proofs (NIZKs). Thanks to their non-interactive nature, NIZKs allow anybody, including third parties that do not participate in the protocol, to verify the correctness of the tally. Therefore, NIZKs can be used to obtain universal verifiability. Additionally, NIZKs also improve usability because they allow voters to cast a vote using a non-interactive protocol. The disadvantage of NIZKs is that their security is based on setup assumptions such as the common reference string (CRS) or the random oracle (RO) model. The former requires a trusted party for the generation of a common reference string. The latter, though a popular methodology for designing secure protocols, has been shown to be unsound.
In this paper, we address the design of an e-voting protocol that provides verifiability without any trust assumptions, where verifiability here is meant without eligibility verification. We show that Non-Interactive Witness-Indistinguishable proofs (NIWI) can be used for this purpose. The e-voting scheme is private under the Decision Linear assumption, while verifiability holds unconditionally. To our knowledge, this is the first private e-voting scheme with perfect universal verifiability, i.e. one in which the probability of a fake tally not being detected is 0, and with non-interactive protocols that does not rely on trust assumptions.

### BibTeX

@article{GIRRR-CoRR16,
abstract =	 {In traditional e-voting protocols, privacy is often
provided by a trusted authority that learns the
votes and computes the tally. Some protocols replace
the trusted authority by a set of authorities, and
privacy is guaranteed if less than a threshold
number of authorities are corrupt. For
verifiability, stronger security guarantees are
demanded. Typically, corrupt authorities that try to
fake the result of the tally must always be
detected. To provide verifiability, many e-voting
protocols use Non-Interactive Zero-Knowledge proofs
(NIZKs). Thanks to their non-interactive nature,
NIZKs allow anybody, including third parties that do
not participate in the protocol, to verify the
correctness of the tally. Therefore, NIZKs can be
used to obtain universal
usability because they allow voters to cast a vote
using a non-interactive protocol. The disadvantage
of NIZKs is that their security is based on setup
assumptions such as the common reference string
(CRS) or the random oracle (RO) model. The former
requires a trusted party for the generation of a
common reference string. The latter, though a
popular methodology for designing secure protocols,
has been shown to be unsound.\par In this paper, we
address the design of an e-voting protocol that
provides verifiability without any trust
assumptions, where verifiability here is meant
without eligibility verification. We show that
Non-Interactive Witness-Indistinguishable proofs
(NIWI) can be used for this purpose.  The e-voting
scheme is private under the Decision Linear
assumption, while verifiability holds
unconditionally. To our knowledge, this is the first
private e-voting scheme with perfect universal
verifiability, i.e. one in which the probability of
a fake tally not being detected is 0, and with {\em
non-interactive} protocols that does not rely on
trust assumptions. },
author =	 {Gina Gallegos{-}Garc{\'{\i}}a and Vincenzo Iovino
and Alfredo Rial and Peter B. R{\o}nne and Peter
Y. A. Ryan},
title =	 {(Universal) Unconditional Verifiability in E-Voting
without Trusted Parties},
journal =	 {CoRR},
volume =	 {abs/1610.06343},
year =	 2016,
url =		 {http://arxiv.org/abs/1610.06343},
lsv-category = {autc},
}