Universally Verifiable MPC with Applications to IRV Ballot Counting

We present a very simple universally verifiable MPC protocol. The first component is a threshold somewhat homomorphic cryptosystem that permits an arbitrary number of additions (in the source group), followed by a single multiplication, followed by an arbitrary number of additions in the target group. The second component is a black-box construction of universally verifiable distributed encryption switching between any public key encryption schemes supporting shared setup and key generation phases, as long as the schemes satisfy some natural additive-homomorphic properties. This allows us to switch back from the target group to the source group, and hence perform an arbitrary number of multiplications. The key generation algorithm of our prototypical cryptosystem, which is based upon concurrent verifiable secret sharing, permits robust re-construction of powers of a shared secret. We demonstrate the scalability of distribution switching as a viable approach to secure vote tallying by implementing a private verifiable form of Instant Runoff Voting on real Australian election data comprising 40,000 votes

Extending the Tally-Hiding Ordinos System: Implementations for Borda, Hare-Niemeyer, Condorcet, and Instant-Runoff Voting

Modern electronic voting systems (e-voting systems) are designed to achieve a variety of security properties, such as verifiability, accountability, and vote privacy. Some of these systems aim at so-called tally-hiding: they compute the election result, according to some result function, like the winner of the election, without revealing any other information to any party. In particular, if desired, they neither reveal the full tally consisting of all (aggregated or even individual) votes nor parts of it, except for the election result, according to the result function. Tally-hiding systems offer many attractive features, such as strong privacy guarantees both for voters and for candidates, and protection against Italian attacks. The Ordinos system is a recent provably secure framework for accountable tally-hiding e-voting that extends Helios and can be instantiated for various election methods and election result functions. So far, practical instantiations and implementations for only rather simple result functions (e.g., computing the $k$ best candidates) and single/multi-vote elections have been developed for Ordinos. In this paper, we propose and implement several new Ordinos instantiations in order to support Borda voting, the Hare-Niemeyer method for proportional representation, multiple Condorcet methods, and Instant-Runoff Voting. Our instantiations, which are based on suitable secure multi-party computation (MPC) components, offer the first tally-hiding implementations for these voting methods. To evaluate the practicality of our MPC components and the resulting e-voting systems, we provide extensive benchmarks for all our implementations

Kryvos: Publicly Tally-Hiding Verifiable E-Voting

Elections are an important corner stone of democratic processes. In addition to publishing the final result (e.g., the overall winner), elections typically publish the full tally consisting of all (aggregated) individual votes. This causes several issues, including loss of privacy for both voters and election candidates as well as so-called Italian attacks that allow for easily coercing voters. Several e-voting systems have been proposed to address these issues by hiding (parts of) the tally. This property is called tally-hiding. Existing tally-hiding e-voting systems in the literature aim at hiding (part of) the tally from everyone, including voting authorities, while at the same time offering verifiability, an important and standard feature of modern e-voting systems which allows voters and external observers to check that the published election result indeed corresponds to how voters actually voted. In contrast, real elections often follow a different common practice for hiding the tally: the voting authorities internally compute (and learn) the full tally but publish only the final result (e.g., the winner). This practice, which we coin publicly tally-hiding, indeed solves the aforementioned issues for the public, but currently has to sacrifice verifiability due to a lack of practical systems. In this paper, we close this gap. We formalize the common notion of publicly tally-hiding and propose the first provably secure verifiable e-voting system, called Kryvos, which directly targets publicly tally-hiding elections. We instantiate our system for a wide range of both simple and complex voting methods and various result functions. We provide an extensive evaluation which shows that Kryvos is practical and able to handle a large number of candidates, complex voting methods and result functions. Altogether, Kryvos shows that the concept of publicly tally-hiding offers a new trade-off between privacy and efficiency that is different from all previous tally-hiding systems and which allows for a radically new protocol design resulting in a practical e-voting system

Sixth International Joint Conference on Electronic Voting E-Vote-ID 2021. 5-8 October 2021

This volume contains papers presented at E-Vote-ID 2021, the Sixth International Joint Conference on Electronic Voting, held during October 5-8, 2021. Due to the extraordinary situation provoked by Covid-19 Pandemic, the conference is held online for second consecutive edition, instead of in the traditional venue in Bregenz, Austria. E-Vote-ID Conference resulted from the merging of EVOTE and Vote-ID and counting up to 17 years since the _rst E-Vote conference in Austria. Since that conference in 2004, over 1000 experts have attended the venue, including scholars, practitioners, authorities, electoral managers, vendors, and PhD Students. The conference collected the most relevant debates on the development of Electronic Voting, from aspects relating to security and usability through to practical experiences and applications of voting systems, also including legal, social or political aspects, amongst others; turning out to be an important global referent in relation to this issue. Also, this year, the conference consisted of: · Security, Usability and Technical Issues Track · Administrative, Legal, Political and Social Issues Track · Election and Practical Experiences Track · PhD Colloquium, Poster and Demo Session on the day before the conference E-VOTE-ID 2021 received 49 submissions, being, each of them, reviewed by 3 to 5 program committee members, using a double blind review process. As a result, 27 papers were accepted for its presentation in the conference. The selected papers cover a wide range of topics connected with electronic voting, including experiences and revisions of the real uses of E-voting systems and corresponding processes in elections. We would also like to thank the German Informatics Society (Gesellschaft für Informatik) with its ECOM working group and KASTEL for their partnership over many years. Further we would like to thank the Swiss Federal Chancellery and the Regional Government of Vorarlberg for their kind support. EVote- ID 2021 conference is kindly supported through European Union's Horizon 2020 projects ECEPS (grant agreement 857622) and mGov4EU (grant agreement 959072). Special thanks go to the members of the international program committee for their hard work in reviewing, discussing, and shepherding papers. They ensured the high quality of these proceedings with their knowledge and experience

Electronic Voting: 6th International Joint Conference, E-Vote-ID 2021, Virtual Event, October 5–8, 2021: proceedings

This volume contains the papers presented at E-Vote-ID 2021, the Sixth International Joint Conference on Electronic Voting, held during October 5–8, 2021. Due to the extraordinary situation brought about by the COVID-19, the conference was held online for the second consecutive edition, instead of in the traditional venue in Bregenz, Austria. The E-Vote-ID conference is the result of the merger of the EVOTE and Vote-ID conferences, with first EVOTE conference taking place 17 years ago in Austria. Since that conference in 2004, over 1000 experts have attended the venue, including scholars, practitioners, authorities, electoral managers, vendors, and PhD students. The conference focuses on the most relevant debates on the development of electronic voting, from aspects relating to security and usability through to practical experiences and applications of voting systems, also including legal, social, or political aspects, amongst others, and has turned out to be an important global referent in relation to this issue

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

Formal Methods for Trustworthy Voting Systems : From Trusted Components to Reliable Software

Voting is prominently an important part of democratic societies, and its outcome may have a dramatic and broad impact on societal progress. Therefore, it is paramount that such a society has extensive trust in the electoral process, such that the system’s functioning is reliable and stable with respect to the expectations within society. Yet, with or without the use of modern technology, voting is full of algorithmic and security challenges, and the failure to address these challenges in a controlled manner may produce fundamental flaws in the voting system and potentially undermine critical societal aspects. In this thesis, we argue for a development process of voting systems that is rooted in and assisted by formal methods that produce transparently checkable evidence for the guarantees that the final system should provide so that it can be deemed trustworthy. The goal of this thesis is to advance the state of the art in formal methods that allow to systematically develop trustworthy voting systems that can be provenly verified. In the literature, voting systems are modeled in the following four comparatively separable and distinguishable layers: (1) the physical layer, (2) the computational layer, (3) the election layer, and (4) the human layer. Current research usually either mostly stays within one of those layers or lacks machine-checkable evidence, and consequently, trusted and understandable criteria often lack formally proven and checkable guarantees on software-level and vice versa. The contributions in this work are formal methods that fill in the trust gap between the principal election layer and the computational layer by a reliable translation of trusted and understandable criteria into trustworthy software. Thereby, we enable that executable procedures can be formally traced back and understood by election experts without the need for inspection on code level, and trust can be preserved to the trustworthy system. The works in this thesis all contribute to this end and consist in five distinct contributions, which are the following: (I) a method for the generation of secure card-based communication schemes, (II) a method for the synthesis of reliable tallying procedures, (III) a method for the efficient verification of reliable tallying procedures, (IV) a method for the computation of dependable election margins for reliable audits, (V) a case study about the security verification of the GI voter-anonymization software. These contributions span formal methods on illustrative examples for each of the three principal components, (1) voter-ballot box communication, (2) election method, and (3) election management, between the election layer and the computational layer. Within the first component, the voter-ballot box communication channel, we build a bridge from the communication channel to the cryptography scheme by automatically generating secure card-based schemes from a small formal model with a parameterization of the desired security requirements. For the second component, the election method, we build a bridge from the election method to the tallying procedure by (1) automatically synthesizing a runnable tallying procedure from the desired requirements given as properties that capture the desired intuitions or regulations of fairness considerations, (2) automatically generating either comprehensible arguments or bounded proofs to compare tallying procedures based on user-definable fairness properties, and (3) automatically computing concrete election margins for a given tallying procedure, the collected ballots, and the computed election result, that enable efficient election audits. Finally, for the third and final component, the election management system, we perform a case study and apply state-of-the-art verification technology to a real-world e-voting system that has been used for the annual elections of the German Informatics Society (GI – “Gesellschaft für Informatik”) in 2019. The case study consists in the formal implementation-level security verification that the voter identities are securely anonymized and the voters’ passwords cannot be leaked. The presented methods assist the systematic development and verification of provenly trustworthy voting systems across traditional layers, i.e., from the election layer to the computational layer. They all pursue the goal of making voting systems trustworthy by reliable and explainable formal requirements. We evaluate the devised methods on minimal card-based protocols that compute a secure AND function for two different decks of cards, a classical knock-out tournament and several Condorcet rules, various plurality, scoring, and Condorcet rules from the literature, the Danish national parliamentary elections in 2015, and a state-of-the-art electronic voting system that is used for the German Informatics Society’s annual elections in 2019 and following

Design and cryptographic security analysis of e-voting protocols

Electronic voting (e-voting) systems are used in numerous countries for political elections, but also for less critical elections within clubs and associations, and hence affect the lives of millions of people. It is therefore important to ensure that single voters' choices remain private, and to be able to verify that an election result coincides with the voters' intention. Unfortunately, for most e-voting systems employed in real elections, these fundamental security and privacy properties cannot be guaranteed, so that in particular the legitimacy of such political elections is challenged. This demonstrates the importance of employing e-voting systems that are rootedly designed to guarantee the required security. However, it turned out to be highly challenging to construct secure yet practical e-voting systems since one always has to find a balance between the (possibly conflicting) requirements of the given kind of election. In the first two chapters of the thesis' main part, we present two practical e-voting systems which are both meant for low-risk and non-political elections, e.g., within clubs or associations. We have implemented both systems to demonstrate their practicability. The first system, called sElect, is designed to be as simple as possible while still guaranteeing a good level of security. The second system, called Ordinos, provides a superior level of privacy as it only reveals the most necessary information about the election outcome, e.g., solely the winner's name but nothing else. We will rigorously analyze the security of sElect and Ordinos. To do this, we formally define the required security properties and then mathematically prove that sElect and Ordinos achieve them. In the third chapter of the thesis' main part, we provide substantial work on the fundamental notion of verifiability of e-voting systems. We analyze and compare all formal verifiability definitions from the literature regarding how meaningful, expressive, or general they are

Ordinos: A Verifiable Tally-Hiding E-Voting System

Modern electronic voting systems (e-voting systems) are designed to provide not only vote privacy but also (end-to-end) verifiability. Several verifiable e-voting systems have been proposed in the literature, with Helios being one of the most prominent ones. Almost all such systems, however, reveal not just the voting result but also the full tally, consisting of the exact number of votes per candidate or even all single votes. There are several situations where this is undesirable. For example, in elections with only a few voters (e.g., boardroom or jury votings), revealing the complete tally leads to a low privacy level, possibly deterring voters from voting for their actual preference. In other cases, revealing the complete tally might unnecessarily embarrass some candidates. Often, the voting result merely consists of a single winner or a ranking of candidates, so revealing only this information but not the complete tally is sufficient. This property is called tally-hiding and it offers completely new options for e-voting. In this paper, we propose the first provably secure end-to-end verifiable tally-hiding e-voting system, called Ordinos. We instantiated our system with suitable cryptographic primitives, including an MPC protocol for greater-than tests, implemented the system, and evaluated its performance, demonstrating its practicality. Moreover, our work provides a deeper understanding of tally-hiding in general, in particular in how far tally-hiding affects the levels of privacy and verifiability of e-voting systems

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