NetVote: A strict-coercion resistance re-voting based internet voting scheme with linear filtering

This paper is an extended of: Querejeta-Azurmendi, I.; Hernández Encinas, L.; Arroyo Guardeño, D.; Hernandez-Ardieta, J.L. An internet voting proposal towards improving usability and coercion resistance. Proceedings of the International Joint Conference: 12th International Conference on Computational Intelligence in Security for Information Systems (CISIS 2019) and 10th International Conference on EUropean Transnational Education (ICEUTE 2019), Seville, Spain, 13-15 May 2019.This paper proposes NetVote, an internet voting protocol where usability and ease in deployment are a priority. We introduce the notion of strict coercion resistance, to distinguish between vote-buying and coercion resistance. We propose a protocol with ballot secrecy, practical everlasting privacy, verifiability and strict coercion resistance in the re-voting setting. Coercion is mitigated via a random dummy vote padding strategy to hide voting patterns and make re-voting deniable. This allows us to build a filtering phase with linear complexity, based on zero knowledge proofs to ensure correctness while maintaining privacy of the process. Voting tokens are formed by anonymous credentials and pseudorandom identifiers, achieving practical everlasting privacy, where even if dealing with a future computationally unbounded adversary, vote intention is still hidden. It is not assumed for voters to own cryptographic keys prior to the election, nor store cryptographic material during the election. This property allows voters not only to vote multiple times, but also from different devices each time, granting the voter a vote-from-anywhere experience. This paper builds on top of the paper published in CISIS'19. In this version, we modify the filtering. Moreover, we formally define the padding technique, which allows us to perform the linear filtering scheme. Similarly we provide more details on the protocol itself and include a section of the security analysis, where we include the formal definitions of strict coercion resistance and a game based definition of practical everlasting privacy. Finally, we prove that NetVote satisfies them all.This research has been partially supported by Ministerio de Economía, Industria y Competitividad (MINECO), Agencia Estatal de Investigación (AEI), and European Regional Development Fund (ERDF, EU), through project COPCIS, grant number TIN2017-84844-C2-1-R, and by Comunidad de Madrid (Spain) through project CYNAMON, grant number P2018/TCS-4566-CM, co-funded along with ERDF

SoK: Secure E-voting with Everlasting Privacy

In this work, we systematically analyze all e-voting protocols designed to provide everlasting privacy. Our main focus is to illustrate their relations and to identify the research problems which have or have not been solved in this area

SoK: Secure E-Voting with Everlasting Privacy

Vote privacy is a fundamental right, which needs to be protected not only during an election, or for a limited time afterwards, but for the foreseeable future. Numerous electronic voting (e-voting) protocols have been proposed to address this challenge, striving for everlasting privacy. This property guarantees that even computationally unbounded adversaries cannot break privacy of past elections. The broad interest in secure e-voting with everlasting privacy has spawned a large variety of protocols over the last three decades. These protocols differ in many aspects, in particular the precise security properties they aim for, the threat scenarios they consider, and the privacy-preserving techniques they employ. Unfortunately, these differences are often opaque, making analysis and comparison cumbersome. In order to overcome this non-transparent state of affairs, we systematically analyze all e-voting protocols designed to provide everlasting privacy. First, we illustrate the relations and dependencies between all these different protocols. Next, we analyze in depth which protocols do provide secure and efficient approaches to e-voting with everlasting privacy under realistic assumptions, and which ones do not. Eventually, based on our extensive and detailed treatment, we identify which research problems in this field have already been solved, and which ones are still open. Altogether, our work offers a well-founded reference point for conducting research on secure e-voting with everlasting privacy as well as for future-proofing privacy in real-world electronic elections

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

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

Election Eligibility with OpenID: Turning Authentication into Transferable Proof of Eligibility

Eligibility checks are often abstracted away or omitted in voting protocols, leading to situations where the voting server can easily stuff the ballot box. One reason for this is the difficulty of bootstraping the authentication material for voters without relying on trusting the voting server. In this paper, we propose a new protocol that solves this problem by building on OpenID, a widely deployed authentication protocol. Instead of using it as a standard authentication means, we turn it into a mechanism that delivers transferable proofs of eligibility. Using zk-SNARK proofs, we show that this can be done without revealing any compromising information, in particular, protecting everlasting privacy. Our approach remains efficient and can easily be integrated into existing protocols, as we have done for the Belenios voting protocol. We provide a full-fledged proof of concept along with benchmarks showing our protocol could be realistically used in large-scale elections

When Are Three Voters Enough for Privacy Properties?

International audienceProtocols for secure electronic voting are of increasing societal importance. Proving rigorously their security is more challenging than many other protocols, which aim at authentication or key exchange. One of the reasons is that they need to be secure for an arbitrary number of malicious voters. In this paper we identify a class of voting protocols for which only a small number of agents needs to be considered: if there is an attack on vote privacy then there is also an attack that involves at most 3 voters (2 honest voters and 1 dishonest voter). In the case where the protocol allows a voter to cast several votes and counts, e.g., only the last one, we also reduce the number of ballots required for an attack to 10, and under some additional hypotheses, 7 ballots. Our results are formalised and proven in a symbolic model based on the applied pi calculus. We illustrate the applicability of our results on several case studies, including different versions of Helios and Prêt-` a-Voter, as well as the JCJ protocol. For some of these protocols we can use the ProVerif tool to provide the first formal proofs of privacy for an unbounded number of voters

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