NM-CPA Secure Encryption with Proofs of Plaintext Knowledge

Smyth, Ben; Hanatani, Yoshikazu; Muratani, Hirofumi

doi:10.1007/978-3-319-22425-1_8

Cited by 4 publications

(3 citation statements)

References 24 publications

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“…Verify recomputes the homomorphic combination, checks the proofs, and outputs 1 if these checks succeed and 0 otherwise. We adopt the formal definition of Helios proposed by Smyth, Frink & Clarkson [SFC16], which adopts non-malleable ballots [SHM15] and uses the Fiat-Shamir transformation with the inclusion of statements in hashes [BPW12a] to defend against those attacks. We recall that formalisation in Appendix F and henceforth refer to it as Helios'16.…”

Section: Tallying By Homomorphic Combinationsmentioning

confidence: 99%

Secret, verifiable auctions from elections

Quaglia

Smyth

2018

Theoretical Computer Science

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Auctions and elections are seemingly disjoint. Nevertheless, similar cryptographic primitives are used in both domains. For instance, mixnets, homomorphic encryption and trapdoor bit-commitments have been used by state-of-the-art schemes in both domains. These developments have appeared independently. For example, the adoption of mixnets in elections preceded a similar adoption in auctions by over two decades. In this paper, we demonstrate a relation between auctions and elections: we present a generic construction for auctions from election schemes. Moreover, we show that the construction guarantees secrecy and verifiability, assuming the underlying election scheme satisfies analogous security properties. We demonstrate the applicability of our work by deriving auction schemes from the Helios family of election schemes. Our results advance the unification of auctions and elections, thereby facilitating the progression of both domains.

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Section: Tallying By Homomorphic Combinationsmentioning

confidence: 99%

Secret, verifiable auctions from elections

Quaglia

Smyth

2018

Theoretical Computer Science

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“…The original scheme [2] is known to be vulnerable to attacks against ballot secrecy and verifiability, 13 and defences against those attacks have been proposed [17,8,39,36]. We adopt the formal definition of a Helios variant by Smyth, Frink & Clarkson [40], which adopts non-malleable ballots [41,36] and uses the Fiat-Shamir transformation with statements in hashes [8] to defend against those attacks. Henceforth, we write Helios'16 to refer to that formalisation.…”

Section: Case Study: a Secret Verifiable Election Scheme With Internmentioning

confidence: 99%

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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“…Using this game, attacks against Helios'12 can be detected [30]. Nonetheless, a variant of Helios [34], henceforth Helios'16, that uses ballots from which meaningfully related ballots cannot be constructed (i.e., non-malleable ballots) [30,35], is not vulnerable to such attacks and is proven to satisfy this formulation of ballot secrecy.…”

Section: Ballot Secrecymentioning

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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NM-CPA Secure Encryption with Proofs of Plaintext Knowledge

Cited by 4 publications

References 24 publications

Secret, verifiable auctions from elections

Secret, verifiable auctions from elections

Authentication with Weaker Trust Assumptions for Voting Systems

A short introduction to secrecy and verifiability for elections

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