(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.

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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
                  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.\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},
}