A two authorities electronic vote scheme

[EN] In this paper we propose a new electronic multi-authority voting system based on blind signatures. We focus on the open problem of the efficiency of electronic voting systems. Most of the proposed systems rely on complex architectures or expensive proofs, in this work we aim to reduce the time-complexity of the voting process, both for the voter and the authorities involved. Our system is focused on simplicity and it is based on the assumption of two unrelated entities. This simplicity makes our approach scalable and flexible to multiple kinds of elections. We propose a method that limits the number of authorities to only 2 of them; we reduce the overall number of modular operations; and, propose a method which cut downs the interactions needed to cast a vote. The result is a voting protocol whose complexity scales linearly with the number of votes.Larriba-Flor, AM.; Sempere Luna, JM.; López Rodríguez, D. (2020). A two authorities electronic vote scheme. Computers & Security. 97:1-12. https://doi.org/10.1016/j.cose.2020.101940S11297Bloom, B. H. (1970). Space/time trade-offs in hash coding with allowable errors. Communications of the ACM, 13(7), 422-426. doi:10.1145/362686.362692Brams S., Fishburn P.C.. 2007. Approval voting Springer ScienceCarroll, T. E., & Grosu, D. (2009). A secure and anonymous voter-controlled election scheme. Journal of Network and Computer Applications, 32(3), 599-606. doi:10.1016/j.jnca.2008.07.010Chaum, D. L. (1981). Untraceable electronic mail, return addresses, and digital pseudonyms. Communications of the ACM, 24(2), 84-90. doi:10.1145/358549.358563Cramer, R., Gennaro, R., & Schoenmakers, B. (1997). A secure and optimally efficient multi-authority election scheme. European Transactions on Telecommunications, 8(5), 481-490. doi:10.1002/ett.4460080506Desmedt, Y. G. (2010). Threshold cryptography. European Transactions on Telecommunications, 5(4), 449-458. doi:10.1002/ett.4460050407Elgamal, T. (1985). A public key cryptosystem and a signature scheme based on discrete logarithms. IEEE Transactions on Information Theory, 31(4), 469-472. doi:10.1109/tit.1985.1057074Juang, W.-S. (2002). A Verifiable Multi-Authority Secret Election Allowing Abstention from Voting. The Computer Journal, 45(6), 672-682. doi:10.1093/comjnl/45.6.672Menezes A., van Oorschot P.C., Vanstone S.A.. 1996. Handbook of Applied Cryptography.Parhami, B. (1994). Voting algorithms. IEEE Transactions on Reliability, 43(4), 617-629. doi:10.1109/24.370218Rabin, M. O. (1980). Probabilistic Algorithms in Finite Fields. SIAM Journal on Computing, 9(2), 273-280. doi:10.1137/0209024Rabin, M. O. (1983). Transaction protection by beacons. Journal of Computer and System Sciences, 27(2), 256-267. doi:10.1016/0022-0000(83)90042-9Salazar, J. L., Piles, J. J., Ruiz-Mas, J., & Moreno-Jiménez, J. M. (2010). Security approaches in e-cognocracy. Computer Standards & Interfaces, 32(5-6), 256-265. doi:10.1016/j.csi.2010.01.004Nguyen, T. A. T., & Dang, T. K. (2013). Enhanced security in internet voting protocol using blind signature and dynamic ballots. Electronic Commerce Research, 13(3), 257-272. doi:10.1007/s10660-013-9120-5Wu, Z.-Y., Wu, J.-C., Lin, S.-C., & Wang, C. (2014). An electronic voting mechanism for fighting bribery and coercion. Journal of Network and Computer Applications, 40, 139-150. doi:10.1016/j.jnca.2013.09.011Yang, X., Yi, X., Nepal, S., Kelarev, A., & Han, F. (2018). A Secure Verifiable Ranked Choice Online Voting System Based on Homomorphic Encryption. IEEE Access, 6, 20506-20519. doi:10.1109/access.2018.2817518Yi, X., & Okamoto, E. (2013). Practical Internet voting system. Journal of Network and Computer Applications, 36(1), 378-387. doi:10.1016/j.jnca.2012.05.00

Security Proofs for Participation Privacy and Stronger Verifiability for Helios

The Helios voting scheme is well studied including formal proofs for verifiability and ballot privacy, but it does not provide participation privacy (i.e. it reveals who participated in the election). Kulyk, Teague and Volkamer proposed an extension to Helios that is claimed to provide ballot privacy as well as participation privacy while providing stronger verifiability than Helios. However, the authors did not prove their claims. Our contribution is to provide a formal definition for participation privacy and to prove that their claims hold

Koinonia: verifiable e-voting with long-term privacy

Despite years of research, many existing e-voting systems do not adequately protect voting privacy. In most cases, such systems only achieve "immediate privacy", that is, they only protect voting privacy against today's adversaries, but not against a future adversary, who may possess better attack technologies like new cryptanalysis algorithms and/or quantum computers. Previous attempts at providing long-term voting privacy (dubbed "everlasting privacy" in the literature) often require additional trusts in parties that do not need to be trusted for immediate privacy. In this paper, we present a framework of adversary models regarding e-voting systems, and analyze possible threats to voting privacy under each model. Based on our analysis, we argue that secret-sharing based voting protocols offer a more natural and elegant privacy-preserving solution than their encryption-based counterparts. We thus design and implement Koinonia, a voting system that provides long-term privacy against powerful adversaries and enables anyone to verify that each ballot is well-formed and the tallying is done correctly. Our experiments show that Koinonia protects voting privacy with a reasonable performance

A foundation for secret, verifiable elections

Many voting systems rely on art, rather than science, to ensure that votes are freely made, with equal influence. Such systems build upon creativity and skill, rather than scientific foundations. These systems are routinely broken in ways that compromise free-choice or permit undue influence. Breaks can be avoided by proving that voting systems satisfy formal notions of voters voting freely and of detecting undue influence. This manuscript provides a detailed technical introduction to a definition of ballot secrecy by Smyth that formalises the former notion and a definition of verifiability by Smyth, Frink & Clarkson that formalises the latter. The definitions are presented in the computational model of cryptography: Ballot secrecy is expressed as the inability to distinguish between an instance of the voting system in which voters cast some votes, from another instance in which the voters cast a permutation of those votes. Verifiability decomposes into individual verifiability, which is expressed as the inability to cause a collision between ballots, and universal verifiability, which is expressed as the inability to cause an incorrect election outcome to be accepted. The definitions are complimented with simple examples that demonstrate the essence of these properties and detailed proofs are constructed to show how secrecy and verifiability can be formally proved. Finally, the Helios and Helios Mixnet voting systems are presented as case studies to provide an understanding of state-of-the-art systems that are being used for binding elections

Distributed attacker: an attacker type proposal for securitu ceremonies

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência da Computação, Florianópolis, 2017Abstract : Security ceremonies are extensions of security protocols, including all that is out-of-bounds for protocols. Nowadays we lack a base description language and a detailed threat model for security ceremonies in order to be able to use symbolic evaluation methods and verify claims embedded in ceremonies. Our goal is to contribute with a syntax and detailed threat model for ceremonies description in order to establish our proposal for a new attacker type named Distributed Attacker (DA in brief). Moreover, we also developed a strategy for symbolic evaluation of our attacker model using First-Order Logic (FOL) and an automatic theorem prover. Lastly, we present scenarios formally analysed with our methodology, including cases we could not have with standard Dolev-Yao or Multi-Attacker models. For instance, our most interesting scenario is when several attackers gather only pieces of an user's credentials and, by putting together their knowledge, collude to attack this user's email account.Protocolos de segurança são subconjuntos das chamadas cerimônias de segurança. Atualmente não se tem uma linguagem de descrição e um modelo de ameaça detalhado para cerimônias de segurança, necessários para o uso de métodos de avaliação simbólica e verificação de suposições presentes em cerimônias. O objetivo desta dissertação é contribuir com uma sintaxe para descrição de mensagens de cerimônias e apropriado modelo de ameaça a fim de estabelecer a proposta para um novo tipo de atacante (nomeado Atacante Distribuído). Adicionalmente, uma estratégia para execução de avaliação simbólica também foi desenvolvida, utilizando lógica de primeira ordem e um provador de teoremas automático. Por fim, cenários formalmente analisados com o modelo de atacante proposto são exibidos, incluindo casos não passíveis de serem simulados com modelos padrão como Dolev-Yao ou Multi-Attacker. Por exemplo, o caso mais interessante é o que apresenta vários atacantes com conhecimento apenas de partes das credenciais de um usuário, mas que ao colaborar entre si conseguem atacar a conta de email desse usuário

SoK: Verifiability Notions for E-Voting Protocols

International audienceThere have been intensive research efforts in the last two decades or so to design and deploy electronic voting (e-voting) protocols and systems which allow voters and/or external auditors to check that the votes were counted correctly. This security property, which not least was motivated by numerous problems in even national elections, is called verifiability. It is meant to defend against voting devices and servers that have programming errors or are outright malicious. In order to properly evaluate and analyze e-voting protocols and systems w.r.t. verifiability, one fundamental challenge has been to formally capture the meaning of this security property. While the first formal definitions of verifiability were devised in the late 1980s already, new verifiability definitions are still being proposed. The definitions differ in various aspects, including the classes of protocols they capture and even their formulations of the very core of the meaning of verifiability. This is an unsatisfying state of affairs, leaving the research on the verifiability of e-voting protocols and systems in a fuzzy state.In this paper, we review all formal definitions of verifiability proposed in the literature and cast them in a framework proposed by Küsters, Truderung, and Vogt (the KTV framework), yielding a uniform treatment of verifiability. This enables us to provide a detailed comparison of the various definitions of verifiability from the literature. We thoroughly discuss advantages and disadvantages, and point to limitations and problems. Finally, from these discussions and based on the KTV framework, we distill a general definition of verifiability, which can be instantiated in various ways, and provide precise guidelines for its instantiation. The concepts for verifiability we develop should be widely applicable also beyond the framework used here. Altogether, our work offers a well-founded reference point for future research on the verifiability of e-voting systems

A Distributed Bulletin Board Implementation for Practical Use in e­-Voting Systems

Tα σύγχρονα συστήματα ηλεκτρονικών ψηφοφοριών χτίζονται γύρω από έναν κεντρικοποιημένο, δημοσίως διαθέσιμο, ψηφιακό Πίνακα Ανακοινώσεων (ΠΑ). Όλα τα αντικείμενα που αναρτώνται στον ΠΑ είναι αυθεντικοποιημένα και δεν πρέπει κανένας να έχει τη δυνατότητα είτε να τα διαγράψει, είτε να τα τροποποιήσει. Ένας ΠΑ μπορεί να αποτελέσει ένα μοναδικό σημείο αποτυχίας ενός συστήματος. Για να αντιμετωπιστεί αυτό το κρίσιμο ζήτημα, μια σειρά από κατανεμημένες προσεγγίσεις έχουν προταθεί για την κατασκευή του ΠΑ. Γενικά, αυτές οι προτάσεις στερούνται είτε διαλειτουργικότητας, διότι είναι στενά συνδεδεμένες με συγκεκριμένα συστήματα ηλεκτρονικών ψηφοφοριών, είτε επιθεώρησης βάσει ενός επίσημου μοντέλου ασφαλείας. Στην παρούσα Διπλωματική Εργασία, ερευνούμε ένα σύνολο προτεινόμενων κατανεμημένων πρωτοκόλλων για ΠΑ, τα οποία δεν πάσχουν από τα προαναφερθέντα ελαττώματα, και αναλύουμε τις ιδιότητες ασφαλείας τους βάσει ενός συγκεκριμένου πλαισίου ασφαλείας. Η προτεινόμενη λύση μας αποτελείται από ένα ανεξάρτητο πλατφόρμας σύνολο δομοστοιχείων λογισμικού, τα οποία όχι μόνο υλοποιούν τα παραπάνω πρωτόκολλα, αλλά μπορούν και να εφαρμοστούν πάνω σε υπάρχοντα συστήματα ηλεκτρονικών ψηφοφοριών. Για την επικύρωση των ανωτέρω, ενσωματώνουμε τη λύση μας στο Zeus, ένα εδραιωμένο, επαληθεύσιμο, διαδικτυακό σύστημα κατάθεσης και καταμέτρησης ψηφοδελτίων. Επιπλέον, διατυπώνουμε βασικές πτυχές της υλοποίησης της προσέγγισής μας και επισημαίνουμε τις παραδοχές της προτεινόμενης λύσης. Στο τέλος, αξιολογούμε της ιδιότητες κλιμακωσιμότητας των ενσωματωμένων πρωτοκόλλων και παρέχουμε μία πειραματική ανάλυση ασφαλείας. Σε αυτήν, προσομοιώνουμε διαφορετικά σενάρια αντιπάλων και αξιολογούμε τις εγγυήσεις που παρέχει αυτή μας η υλοποίηση των πρωτοκόλλων για ΠΑ.Contemporary e-voting systems are built around a central, publicly accessible, digital Bulletin Board (BB). All items posted to a BB are authenticated and no entity should be able to either erase or modify them. However, the BB can be a potential single point of failure. To address this issue, a number of distributed approaches have been proposed for the make up of BBs. By and large, such proposals lack either interoperability as they are tied to specific e-voting systems or a review under a formal security model. In this thesis, we discuss a set of proposed distributed BB protocols that do not suffer from the above shortcomings and analyze their security properties based on a specific security framework. Our solution consists of a platform-independent set of modules that not only realize the above BB protocols but also can be applied on top of existing e-voting systems. As a proof of concept, we integrate our solution into Zeus, a well-established verifiable internet ballot casting and counting system. Moreover, we articulate key implementation aspects of our approach and underline the assumptions of our solution. Finally, we evaluate the scalability properties of the integrated protocols and provide an experimental security analysis. In this context, we simulate different adversarial scenarios and assess the guarantees that our realization of the BB protocols yields

Ceremonies for End-to-End Verifiable Elections

State-of-the-art e-voting systems rely on voters to perform certain actions to ensure that the election authorities are not manipulating the election result. This so-called “end-to-end (E2E) verifiability” is the hallmark of current e-voting protocols; nevertheless, thorough analysis of current systems is still far from being complete. In this work, we initiate the study of e-voting protocols as ceremonies. A ceremony, as introduced by Ellison [23], is an extension of the notion of a protocol that includes human participants as separate nodes of the system that should be taken into account when performing the security analysis. that centers on the two properties of end-to-end verifiability and voter privacy and allows the consideration of arbitrary behavioural distributions for the human participants. We then analyse the Helios system as an e-voting ceremony. Security in the e-voting ceremony model requires the specification of a class of human behaviours with respect to which the security properties can be preserved. We show how end-to-end verifiability and voter privacy are sensitive to human behaviour in the protocol by characterizing the set of behaviours under which the security can be preserved and also showing explicit scenarios where it fails. We then provide experimental evaluation with human subjects from two different sources where people used Helios: the elections of the International Association for Cryptologic Research (IACR) and a poll of senior year computer science students. We report on the auditing behaviour of the participants as we measured it and we discuss the effects on the level of certainty that can be given by each of the two electorates. The outcome of our analysis is a negative one: the auditing behaviour of people (including cryptographers) is not sufficient to ensure the correctness of the tally with good probability in either case studied. The same holds true even for simulated data that capture the case of relatively well trained participants while, finally, the security of the ceremony can be shown but under the assumption of essentially ideally behaving human subjects. We note that while our results are stated for Helios, they automatically transfer to various other e-voting systems that, as Helios, rely on client-side encryption to encode the voter’s choice