Verifiability of Helios Mixnet

Smyth, Ben

doi:10.1007/978-3-662-58820-8_17

Cited by 5 publications

(3 citation statements)

References 24 publications

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“…For instance, Smyth, Frink & Clarkson [34] have shown that neither Helios-C (an extension of Helios) [9] nor JCJ (an election scheme achieving coercion resistance) [16] satisfy the definition of universal verifiability, and propose a variant of JCJ that does. Moreover, Smyth has shown that implementations of the mixnet variant of Helios do not satisfy universal verifiability, and proposes a variant that satisfies both universal verifiability [32] and ballot secrecy [30].…”

Section: Closing Remarksmentioning

confidence: 99%

A short introduction to secrecy and verifiability for elections

Quaglia,

Smyth

2017

Preprint

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Many election schemes rely on art, rather than science, to ensure that choices are made freely and with equal influence. Such schemes build upon creativity and skill, rather than scientific foundations. These schemes are typically broken in ways that compromise free choice, e.g., [12,7,40,41,36], or permit adversaries to unduly influence the outcome, e.g., [15,11,7,37]. This article shows how such breaks can be avoided by carefully formulating security definitions, and proving that schemes satisfy these definitions. Equipped with these definitions, we can build election schemes that can be proven to behave as expected.An election scheme is a decision-making mechanism to choose a representative [21,27,13,3], typically consisting of at least the following three steps. First, an administrator initialises the scheme (setup). Secondly, each voter constructs and casts a ballot for their choice (voting). These ballots are authenticated and recorded using a mechanism, e.g., a bulletin board. Thirdly, the administrator tallies the recorded ballots and announces an outcome, i.e., a frequency distribution of choices (tallying). This distribution is used to select a representative. For example, in first-pastthe-post election schemes the representative corresponds to the choice with highest frequency.Choices must be made freely, which can be achieved by making choices in private [38,25,24], i.e., "when numerous social constraints in which citizens are routinely and universally enmeshed -community of religious allegiances, the patronage of big men, employers or notables, parties, 'political machines' -are kept at bay" [6]. This has led to the emergence of the following requirement.• Ballot secrecy: a voter's choice is not revealed to anyone.Ballot secrecy ensures that a voter's choice is kept secret, which is intended to prevent unwanted consequences (including the preclusion of free choice) that might otherwise arise.To illustrate how ballot secrecy can be achieved, we introduce a simple election scheme that instructs voters to encrypt their choices and instructs administrators to decrypt encrypted choices to obtain the outcome. More specifically, the scheme works as follows: first, the administrator generates a public key. Secondly, each voter encrypts their choice using that key. Finally, the administrator decrypts each encrypted choice and outputs the corresponding outcome. Intuitively, ballot secrecy is achieved if the underlying encryption scheme is secure, i.e., the encryption of a choice leaks no information about that choice.Voters, and any other interested parties, must be able to convince themselves that the announced outcome is indeed the distribution of choices made by voters, which can be achieved by making elections verifiable, i.e., ensuring "there [is] enough evidence for anyone who doubts the results to re-examine and rationally determine whether the [outcome was] called correctly" [39]. Election verifiability can be captured by the following requirements.

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Section: Closing Remarksmentioning

confidence: 99%

A short introduction to secrecy and verifiability for elections

Quaglia,

Smyth

2017

Preprint

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“… Smyth [38] shows that vulnerabilities in Helios cause vulnerabilities in implementations of the mixnet variant and proves verifiability is satisfied when a fix is applied.…”

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confidence: 92%

Authentication with Weaker Trust Assumptions for Voting Systems

Quaglia

Smyth

2018

Progress in Cryptology – AFRICACRYPT 2018

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Some voting systems are reliant on external authentication services. Others use cryptography to implement their own. We combine digital signatures and non-interactive proofs to derive a generic construction for voting systems with their own authentication mechanisms, from systems that rely on external authentication services. We prove that our construction produces systems satisfying ballot secrecy and election verifiability, assuming the underlying voting system does. Moreover, we observe that works based on similar ideas provide neither ballot secrecy nor election verifiability. Finally, we demonstrate applicability of our results by applying our construction to the Helios voting system.

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“…The definitions we have formally verified are inspired by Smyth et al [41]; specifically, we formally verify that the cryptographic verifier we generate guarantees both the correctness and soundness aspect of the universal verifiability of the scheme. This is the best that can be achieved for a scheme like Helios where castas-intended and collected-as-cast verifiability are not universally verifiable.…”

Section: Introductionmentioning

confidence: 99%

Verified Verifiers for Verifying Elections

Haines

Goré

Tiwari

2019

Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security

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The security and trustworthiness of elections is critical to democracy; alas, securing elections is notoriously hard. Powerful cryptographic techniques for verifying the integrity of electronic voting have been developed and are in increasingly common use. The claimed security guarantees of most of these techniques have been formally proved. However, implementing the cryptographic verifiers which utilise these techniques is a technical and error prone process, and often leads to critical errors appearing in the gap between the implementation and the formally verified design.We significantly reduce the gap between theory and practice by using machine checked proofs coupled with code extraction to produce cryptographic verifiers that are themselves formally verified. We demonstrate the feasibility of our technique by producing a formally verified verifier which we use to check the 2018 International Association for Cryptologic Research (IACR) directors election.

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Verifiability of Helios Mixnet

Cited by 5 publications

References 24 publications

A short introduction to secrecy and verifiability for elections

A short introduction to secrecy and verifiability for elections

Authentication with Weaker Trust Assumptions for Voting Systems

Verified Verifiers for Verifying Elections

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