82 research outputs found
Universally Verifiable Poll-Site Voting Schemes Providing Everlasting Privacy
Computer based voting brings up huge challenges for technology. On the one hand an electronic voting system has to be transparent enough to allow verification of its correct functioning; on the other hand, it must ensure that these verification procedures do not allow an attacker to violate voter privacy. Both requirements can be addressed by providing cryptographically secured voting receipts. Each voter cast his or her vote in encoded form and receives a copy of the recorded ballot as receipt. The voters can use these receipts to verify that their vote is contained in the input of the tally. Furthermore, the encoded votes are publicly processed, which allows voters and observers to check that the election outcome has been determined correctly. However, to provide a private and free election, no voter should be able to prove to someone else for whom he or she voted. This must not only be prevented during the election, but also afterwards for an indefinite period of time. Especially with respect to everlasting privacy this is not ensured by most verifiable voting systems. If the receipt contains, for instance, the voting decision encrypted using some public key cryptography, an attacker can determine the candidates selected as soon as the underlying computational problem has been solved for the key length chosen. In this work we provide a summary of privacy weaknesses that may arise in verifiable electronic poll-site voting systems, and we identify and solve open issues. More precisely, we concentrate on the following three questions: (1) How can we show correct anonymization of votes in an efficient and privacy preserving manner using a generic approach? (2) How can we introduce everlasting privacy to mixing and homomorphic tallying based voting schemes? (3) How can we reduce the amount of trust voters have to put in authorities regarding privacy? In electronic voting so-called reencryption mix-nets are used to anonymize votes. These mix-nets shuffles votes in a universally verifiable manner, i.e., they publish some audit information allowing voters and observers to verify that the votes came out as they went in. In practice, mostly generic verification procedures are used to show correctness of this process. However, many of them do not provide an adequate level of privacy. To address (1), we investigate several proposals and introduce a new protocol that combines existing approaches but improves them with respect to privacy and efficiency. Another drawback of mixing based voting schemes is that all implementations provide computational privacy only. We address (2) by presenting a mix-net that uses a homomorphic and unconditionally hiding commitment scheme to encode the votes and audit data, implying everlasting privacy. The correctness of the anonymization process is guaranteed with overwhelming probability, even if all authorities collaborate. An implication of our result is that many current voting systems that use mix-nets can be upgraded to everlasting privacy. Subsequently, we show that this protocol can be applied to Prêt à Voter and Split-Ballot imposing only minor changes to current implementations. The same approach is used to introduce everlasting privacy to homomorphic tallying based schemes. The votes are encoded with an unconditionally hiding commitment scheme, they are homomorphically tallied in public, and the result is decoded afterwards. To show that our solution can be applied to poll-site voting, we describe how the Scratch & Vote voting system can be improved using our tallying protocol. Again only minor changes to the classical scheme are necessary. To address (3), the approach of non-personalized receipts is analyzed. If the receipts handed out to the voters do not contain a link to their vote cast, they do not have to put their trust in authorities keeping this association secret. We introduce an electronic ballot box that generates non-personalized receipts using a process that is similar to the anonymization procedure carried out by mix-nets. The correctness of the receipt generation is universally verifiable. Furthermore, our approach improves on existing solutions with respect to correctness and privacy. Finally, we compare all voting systems that are improved in this work, highlight their advantages and disadvantages, and conclude with key issues for future work
Seventh International Joint Conference on Electronic Voting
This volume contains papers presented at E-Vote-ID 2022, the Seventh International JointConference on Electronic Voting, held during October 4–7, 2022. This was the first in-personconference following the COVID-19 pandemic, and, as such, it was a very special event forthe community since we returned to the traditional venue in Bregenz, Austria. The E-Vote-IDconference resulted from merging EVOTE and Vote-ID, and 18 years have now elapsed sincethe first EVOTE conference in Austria.Since that conference in 2004, over 1500 experts have attended the venue, including scholars,practitioners, authorities, electoral managers, vendors, and PhD students. E-Vote-ID collectsthe most relevant debates on the development of electronic voting, from aspects relating tosecurity and usability through to practical experiences and applications of voting systems, alsoincluding legal, social, or political aspects, amongst others, turning out to be an importantglobal referent on these issues
Blockchain, consensus, and cryptography in electronic voting
Motivated by the recent trends to conduct electronic elections using blockchain technologies, we review the vast literature on cryptographic voting and assess the status of the field. We analyze the security requirements for voting systems and describe the major ideas behind the most influential cryptographic protocols for electronic voting. We focus on the great importance of consensus in the elimination of trusted third parties. Finally, we examine whether recent blockchain innovations can satisfy the strict requirements set for the security of electronic voting
DeVoS: Deniable Yet Verifiable Vote Updating
peer reviewedInternet voting systems are supposed to meet the same high standards as traditional paper-based systems when used in real political elections: freedom of choice, universal and equal suffrage, secrecy of the ballot, and independent verifiability of the election result. Although numerous Internet voting systems have been proposed to achieve these challenging goals simultaneously, few come close in reality.
We propose a novel publicly verifiable and practically efficient Internet voting system, DeVoS, that advances the state of the art. The main feature of DeVoS is its ability to protect voters' freedom of choice in several dimensions. First, voters in DeVoS can intuitively update their votes in a way that is deniable to observers but verifiable by the voters; in this way voters can secretly overwrite potentially coerced votes. Second, in addition to (basic) vote privacy, DeVoS also guarantees strong participation privacy by end-to-end hiding which voters have submitted ballots and which have not. Finally, DeVoS is fully compatible with Perfectly Private Audit Trail, a state-of-the-art Internet voting protocol with practical everlasting privacy. In combination, DeVoS offers a new way to secure free Internet elections with strong and long-term privacy properties
DeVoS: Deniable Yet Verifiable Vote Updating
Internet voting systems are supposed to meet the same high standards as traditional paper-based systems when used in real political elections: freedom of choice, universal and equal suffrage, secrecy of the ballot, and independent verifiability of the election result. Although numerous Internet voting systems have been proposed to achieve these challenging goals simultaneously, few come close in reality.
We propose a novel publicly verifiable and practically efficient Internet voting system, DeVoS, that advances the state of the art. The main feature of DeVoS is its ability to protect voters\u27 freedom of choice in several dimensions. First, voters in DeVoS can intuitively update their votes in a way that is deniable to observers but verifiable by the voters; in this way voters can secretly overwrite potentially coerced votes. Second, in addition to (basic) vote privacy, DeVoS also guarantees strong participation privacy by end-to-end hiding which voters have submitted ballots and which have not. Finally, DeVoS is fully compatible with Perfectly Private Audit Trail, a state-of-the-art Internet voting protocol with practical everlasting privacy. In combination, DeVoS offers a new way to secure free Internet elections with strong and long-term privacy properties
Matters of Coercion-Resistance in Cryptographic Voting Schemes
This work addresses coercion-resistance in cryptographic voting schemes. It focuses on three particularly challenging cases: write-in candidates, internet elections and delegated voting. Furthermore, this work presents a taxonomy for analyzing and comparing a huge variety of voting schemes, and presents practical experiences with the voting scheme Bingo Voting
Cryptographic Protocols for Privacy Enhancing Technologies: From Privacy Preserving Human Attestation to Internet Voting
Desire of privacy is oftentimes associated with the intention to hide certain
aspects of our thoughts or actions due to some illicit activity. This is a
narrow understanding of privacy, and a marginal fragment of the motivations
for undertaking an action with a desired level of privacy. The right for not
being subject to arbitrary interference of our privacy is part of the universal
declaration of human rights (Article 12) and, above that, a requisite for
our freedom. Developing as a person freely, which results in the development
of society, requires actions to be done without a watchful eye. While
the awareness of privacy in the context of modern technologies is not widely
spread, it is clearly understood, as can be seen in the context of elections,
that in order to make a free choice one needs to maintain its privacy. So
why demand privacy when electing our government, but not when selecting
our daily interests, books we read, sites we browse, or persons we encounter?
It is popular belief that the data that we expose of ourselves would not be
exploited if one is a law-abiding citizen. No further from the truth, as this
data is used daily for commercial purposes: users’ data has value. To make
matters worse, data has also been used for political purposes without the
user’s consent or knowledge. However, the benefits that data can bring to
individuals seem endless and a solution of not using this data at all seems
extremist. Legislative efforts have tried, in the past years, to provide mechanisms
for users to decide what is done with their data and define a framework
where companies can use user data, but always under the consent of the latter.
However, these attempts take time to take track, and have unfortunately
not been very successful since their introduction.
In this thesis we explore the possibility of constructing cryptographic protocols
to provide a technical, rather than legislative, solution to the privacy
problem. In particular we focus on two aspects of society: browsing and
internet voting. These two events shape our lives in one way or another, and
require high levels of privacy to provide a safe environment for humans to
act upon them freely. However, these two problems have opposite solutions.
On the one hand, elections are a well established event in society that has
been around for millennia, and privacy and accountability are well rooted
requirements for such events. This might be the reason why its digitalisation
is something which is falling behind with respect to other acts of our society
(banking, shopping, reading, etc). On the other hand, browsing is a recently
introduced action, but that has quickly taken track given the amount of possibilities
that it opens with such ease. We now have access to whatever we
can imagine (except for voting) at the distance of a click. However, the data
that we generate while browsing is extremely sensitive, and most of it is disclosed to third parties under the claims of making the user experience better
(targeted recommendations, ads or bot-detection).
Chapter 1 motivates why resolving such a problem is necessary for the
progress of digital society. It then introduces the problem that this thesis
aims to resolve, together with the methodology. In Chapter 2 we introduce
some technical concepts used throughout the thesis. Similarly, we expose the
state-of-the-art and its limitations.
In Chapter 3 we focus on a mechanism to provide private browsing. In
particular, we focus on how we can provide a safer, and more private way, for
human attestation. Determining whether a user is a human or a bot is important
for the survival of an online world. However, the existing mechanisms
are either invasive or pose a burden to the user. We present a solution that
is based on a machine learning model to distinguish between humans and
bots that uses natural events of normal browsing (such as touch the screen
of a phone) to make its prediction. To ensure that no private data leaves
the user’s device, we evaluate such a model in the device rather than sending
the data over the wire. To provide insurance that the expected model has
been evaluated, the user’s device generates a cryptographic proof. However
this opens an important question. Can we achieve a high level of accuracy
without resulting in a noneffective battery consumption? We provide a positive
answer to this question in this work, and show that a privacy-preserving
solution can be achieved while maintaining the accuracy high and the user’s
performance overhead low.
In Chapter 4 we focus on the problem of internet voting. Internet voting
means voting remotely, and therefore in an uncontrolled environment.
This means that anyone can be voting under the supervision of a coercer,
which makes the main goal of the protocols presented to be that of coercionresistance.
We need to build a protocol that allows a voter to escape the
act of coercion. We present two proposals with the main goal of providing
a usable, and scalable coercion resistant protocol. They both have different
trade-offs. On the one hand we provide a coercion resistance mechanism
that results in linear filtering, but that provides a slightly weaker notion of
coercion-resistance. Secondly, we present a mechanism with a slightly higher
complexity (poly-logarithmic) but that instead provides a stronger notion of
coercion resistance. Both solutions are based on a same idea: allowing the
voter to cast several votes (such that only the last one is counted) in a way
that cannot be determined by a coercer.
Finally, in Chapter 5, we conclude the thesis, and expose how our results
push one step further the state-of-the-art. We concisely expose our contributions,
and describe clearly what are the next steps to follow. The results
presented in this work argue against the two main claims against privacy preserving solutions: either that privacy is not practical or that higher levels
of privacy result in lower levels of security.Programa de Doctorado en Ciencia y Tecnología Informática por la Universidad Carlos III de MadridPresidente: Agustín Martín Muñoz.- Secretario: José María de Fuentes García-Romero de Tejada.- Vocal: Alberto Peinado Domíngue
Secure multi party computations for electronic voting
Στην παρούσα εργασία, μελετούμε το πρόβλημα της ηλεκτρονικής ψηφοφορίας.
Θεωρούμε ότι είναι έκφανση μιας γενικής διαδικασίας αποφάσεων που μπορεί να
υλοποιηθεί μέσω υπολογισμών πολλαπλών οντοτήτων, οι οποίοι πρέπει να
ικανοποιούν πολλές και αντικρουόμενες απαιτήσεις ασφαλείας.
Έτσι μελετούμε σχετικές προσεγγίσεις οι οποίες βασιζονται σε κρυπτογραφικές
τεχνικές, όπως τα ομομορφικά κρυπτοσυστήματα, τα δίκτυα μίξης και οι τυφλές
υπογραφές. Αναλύουμε πώς προσφέρουν ακεραιότητα και ιδιωτικότητα (μυστικότητα)
στην διαδικασία και την σχέση τους με την αποδοτικότητα. Εξετάζουμε τα είδη
λειτουργιών κοινωνικής επιλογής που μπορούν να υποστηρίξουν και παρέχουμε δύο
υλοποιήσεις. Επιπλέον ασχολούμαστε με την αντιμετώπιση ισχυρότερων αντιπάλων μη
παρέχοντας αποδείξεις ψήφου ή προσφέροντας δυνατότητες αντίστασης στον
εξαναγκασμό. Με βάση την τελευταία έννοια προτείνουμε μια τροποποίηση σε ένα
ευρέως χρησιμοποιούμενο πρωτόκολλο. Τέλος μελετούμε δύο γνωστές υλοποιήσεις
συστημάτων ηλεκτρονικής ψηφοφοριας το Helios και το Pret a Voter .In this thesis, we study the problem of electronic voting as a general decision
making process that can be implemented using multi party computations,
fulfilling strict and often conflicting security requirements. To this end, we
review relevant cryptographic techniques and their combinations to form voting
protocols. More specifically, we analyze schemes based on homomorphic
cryptosystems, mixnets with proofs of shuffles and blind signatures. We analyze
how they achieve integrity and privacy in the voting process, while keeping
efficiency. We examine the types of social choice functions that can be
supported by each protocol. We provide two proof of concept implementations.
Moreover, we review ways to thwart stronger adversaries by adding receipt
freeness and coercion resistance to voting systems. We build on the latter
concept to propose a modification to a well known protocol. Finally, we study
two actual e-Voting implementations namely Helios and Pret a Voter
VeriVoting: A decentralized, verifiable and privacy-preserving scheme for weighted voting
Decentralization, verifiability, and privacy-preserving are three fundamental properties of modern e-voting. In this paper, we conduct extensive investigations into them and present a novel e-voting scheme, VeriVoting, which is the first to satisfy these properties. More specifically, decentralization is realized through blockchain technology and the distribution of decryption power among competing entities, such as candidates. Furthermore, verifiability is satisfied when the public verifies the ballots and decryption keys. And finally, bidirectional unlinkability is achieved to help preserve privacy by decoupling voter identity from ballot content. Following the ideas above, we first leverage linear homomorphic encryption schemes and non-interactive zero-knowledge argument systems to construct a voting primitive, SemiVoting, which meets decentralization, decryption-key verifiability, and ballot privacy. To further achieve ballot ciphertext verifiability and anonymity, we extend this primitive with blockchain and verifiable computation to finally arrive at VeriVoting. Through security analysis and per-formance evaluations, VeriVoting offers a new trade-off between security and efficiency that differs from all previous e-voting schemes and provides a radically novel practical ap-proach to large-scale elections
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