372 results sorted by ID
Hyperion: Transparent End-to-End Verifiable Voting with Coercion Mitigation
Aditya Damodaran, Simon Rastikian, Peter B. Rønne, Peter Y A Ryan
Cryptographic protocols
We present Hyperion, an end-to-end verifiable e-voting scheme that allows the voters to identify their votes in cleartext in the final tally. In contrast to schemes like Selene or sElect, identification is not via (private) tracker numbers but via cryptographic commitment terms. After publishing the tally, the Election Authority provides each voter with an individual dual key. Voters identify their votes by raising their dual key to their secret trapdoor key and finding the matching...
Grafted Trees Bear Better Fruit: An Improved Multiple-Valued Plaintext-Checking Side-Channel Attack against Kyber
Jinnuo Li, Chi Cheng, Muyan Shen, Peng Chen, Qian Guo, Dongsheng Liu, Liji Wu, Jian Weng
Attacks and cryptanalysis
As a prominent category of side-channel attacks (SCAs), plaintext-checking (PC) oracle-based SCAs offer the advantages of generality and operational simplicity on a targeted device. At TCHES 2023, Rajendran et al. and Tanaka et al. independently proposed the multiple-valued (MV) PC oracle, significantly reducing the required number of queries (a.k.a., traces) in the PC oracle. However, in practice, when dealing with environmental noise or inaccuracies in the waveform classifier, they...
Expanding the Toolbox: Coercion and Vote-Selling at Vote-Casting Revisited
Tamara Finogina, Javier Herranz, Peter B. Roenne
Applications
Coercion is a challenging and multi-faceted threat that prevents people from expressing their will freely. Similarly, vote-buying does to undermine the foundation of free democratic elections. These threats are especially dire for remote electronic voting, which relies on voters to express their political will freely but happens in an uncontrolled environment outside the polling station and the protection of the ballot booth. However, electronic voting in general, both in-booth and remote,...
Practical Traceable Receipt-Free Encryption
Henri Devillez, Olivier Pereira, Thomas Peters
Public-key cryptography
Traceable Receipt-free Encryption (TREnc) is a verifiable public-key encryption primitive introduced at Asiacrypt 2022. A TREnc allows randomizing ciphertexts in transit in order to remove any subliminal information up to a public trace that ensures the non-malleability of the underlying plaintext. A remarkable property of TREnc is the indistinguishability of the randomization of chosen ciphertexts against traceable chosen-ciphertext attacks (TCCA). This property can support applications...
Faster Asynchronous Blockchain Consensus and MVBA
Matthieu Rambaud
Applications
Blockchain consensus, a.k.a. BFT SMR, are protocols enabling $n$ processes to decide on an ever-growing chain. The fastest known asynchronous one is called 2-chain VABA (PODC'21 and FC'22), and is used as fallback chain in Abraxas* (CCS'23). It has a claimed $9.5\delta$ expected latency when used for a single shot instance, a.k.a. an MVBA.
We exhibit attacks breaking it. Hence, the title of the fastest asynchronous MVBA with quadratic messages complexity goes to sMVBA (CCS'22), with...
Shuffle Arguments Based on Subset-Checking
Behzad Abdolmaleki, Prastudy Fauzi, Toomas Krips, Janno Siim
Cryptographic protocols
Zero-knowledge shuffle arguments are a useful tool for constructing mix-nets which enable anonymous communication. We propose a new shuffle argument using a novel technique that probabilistically checks that each weighted set of input elements corresponds to some weighted set of output elements, with weights from the same set as the input element weights. We achieve this using standard discrete log assumptions and the shortest integer solution (SIS) assumption. Our shuffle argument has...
PeaceFounder: centralised E2E verifiable evoting via pseudonym braiding and history trees
Janis Erdmanis
Cryptographic protocols
PeaceFounder is a centralised E2E verifiable e-voting system that leverages pseudonym braiding and history trees. The immutability of the bulletin board is maintained replication-free by voter’s client devices with locally stored consistency-proof chains. Meanwhile, pseudonym braiding done via an exponentiation mix before the vote allows anonymisation to be transactional with a single braider at a time. In contrast to existing E2E verifiable e-voting systems, it is much easier to deploy as...
Tempora-Fusion: Time-Lock Puzzle with Efficient Verifiable Homomorphic Linear Combination
Aydin Abadi
To securely transmit sensitive information into the future, Time-Lock Puzzles (TLPs) have been developed. Their applications include scheduled payments, timed commitments, e-voting, and sealed-bid auctions. Homomorphic TLP is a key variant of TLP that enables computation on puzzles from different clients. This allows a solver/server to tackle only a single puzzle encoding the computation's result. However, existing homomorphic TLPs lack support for verifying the correctness of the...
zkVoting : Zero-knowledge proof based coercion-resistant and E2E verifiable e-voting system
Seongho Park, Jaekyoung Choi, Jihye Kim, Hyunok Oh
Applications
We introduce ${zkVoting}$, a coercion-resistant e-voting system that utilizes a fake keys approach based on a novel nullifiable commitment scheme. This scheme allows voters to receive both real and fake commitment keys from a registrar. Each ballot includes this commitment, but only the tallier can efficiently discern the fake ballots, simplifying the tally process to $\mathcal{O}(n)$ and ensuring coercion resistance. ${zkVoting}$ also preserves voter anonymity by ensuring each ballot...
Signer Revocability for Threshold Ring Signatures
Da Teng, Yanqing Yao
Public-key cryptography
t-out-of-n threshold ring signature (TRS) is a type of anonymous signature designed for t signers to jointly sign a message while hiding their identities among n parties that include themselves. However, can TRS address those needs if one of the signers wants to revoke his signature or, additively, sign separately later? Can non-signers be revoked without compromising anonymity? Previous research has only discussed opposing situations. The present study introduces a novel property for...
ElectionGuard: a Cryptographic Toolkit to Enable Verifiable Elections
Josh Benaloh, Michael Naehrig, Olivier Pereira, Dan S. Wallach
Applications
ElectionGuard is a flexible set of open-source tools that---when used with traditional election systems---can produce end-to-end verifiable elections whose integrity can be verified by observers, candidates, media, and even voters themselves. ElectionGuard has been integrated into a variety of systems and used in actual public U.S. elections in Wisconsin, California, Idaho, Utah, and Maryland as well as in caucus elections in the U.S. Congress. It has also been used for civic voting in the...
Verifiable and Private Vote-by-Mail
Henri Devillez, Olivier Pereira, Thomas Peters
Cryptographic protocols
Vote-by-mail is increasingly used in Europe and worldwide for government elections. Nevertheless, very few attempts have been made towards the design of verifiable vote-by-mail, and none of them come with a rigorous security analysis. Furthermore, the ballot privacy of the currently deployed (non-verifiable) vote-by-mail systems relies on procedural means that a single malicious operator can bypass.
We propose a verifiable vote-by-mail system that can accommodate the constraints of many...
REACTIVE: Rethinking Effective Approaches Concerning Trustees in Verifiable Elections
Josh Benaloh, Michael Naehrig, Olivier Pereira
Applications
For more than forty years, two principal questions have been asked when designing verifiable election systems: how will the integrity of the results be demonstrated and how will the privacy of votes be preserved? Many approaches have been taken towards answering the first question such as use of MixNets and homomorphic tallying. But in the academic literature, the second question has always been answered in the same way: decryption capabilities are divided amongst multiple independent...
Efficient Universally-Verifiable Electronic Voting with Everlasting Privacy
David Pointcheval
Cryptographic protocols
Universal verifiability is a must-to-have for electronic voting schemes. It is essential to ensure honest behavior of all the players during the whole process, together with the eligibility. However, it should not endanger the privacy of the individual votes, which is another major requirement.
Whereas the first property prevents attacks during the voting process, privacy of the votes should hold forever, which has been called everlasting privacy.
A classical approach for universal...
Greco: Fast Zero-Knowledge Proofs for Valid FHE RLWE Ciphertexts Formation
Enrico Bottazzi
Cryptographic protocols
Fully homomorphic encryption (FHE) allows for evaluating arbitrary functions over encrypted data. In Multi-party FHE applications, different parties encrypt their secret data and submit ciphertexts to a server, which, according to the application logic, performs homomorphic operations on them. For example, in a secret voting application, the tally is computed by summing up the ciphertexts encoding the votes. Valid encrypted votes are of the form $E(0)$ and $E(1)$. A malicious voter could...
LLRing: Logarithmic Linkable Ring Signatures with Transparent Setup
Xiangyu Hui, Sid Chi-Kin Chau
Cryptographic protocols
Linkable ring signatures are an important cryptographic primitive for anonymized applications, such as e-voting, e-cash and confidential transactions. To eliminate backdoor and overhead in a trusted setup, transparent setup in the discrete logarithm or pairing settings has received considerable attention in practice. Recent advances have improved the proof sizes and verification efficiency of linkable ring signatures with a transparent setup to achieve logarithmic bounds. Omniring (CCS '19)...
Column-wise Garbling, and How to Go Beyond the Linear Model
Lei Fan, Zhenghao Lu, Hong-Sheng Zhou
Cryptographic protocols
In the linear garbling model introduced by Zahur, Rosulek, and Evans (Eurocrypt 2015), garbling an AND gate requires at least \(2\kappa\) bits of ciphertext, where $\kappa$ is the security parameter. Though subsequent works, including those by Rosulek and Roy (Crypto 2021) and Acharya et al. (ACNS 2023), have advanced beyond these linear constraints, a more comprehensive design framework is yet to be developed.
Our work offers a novel, unified, and arguably simple perspective on garbled...
SyRA: Sybil-Resilient Anonymous Signatures with Applications to Decentralized Identity
Elizabeth Crites, Aggelos Kiayias, Markulf Kohlweiss, Amirreza Sarencheh
Cryptographic protocols
We introduce a new cryptographic primitive, called Sybil-Resilient Anonymous (SyRA) signatures, which enable users to generate, on demand, unlinkable pseudonyms tied to any given context, and issue signatures on behalf of these pseudonyms. Concretely, given a personhood relation, an issuer (who may be a distributed entity) enables users to prove their personhood and extract an associated long-term key, which can then be used to issue signatures for any given context and message....
A Two-Layer Blockchain Sharding Protocol Leveraging Safety and Liveness for Enhanced Performance
Yibin Xu, Jingyi Zheng, Boris Düdder, Tijs Slaats, Yongluan Zhou
Cryptographic protocols
Sharding is a critical technique that enhances the scalability of blockchain technology. However, existing protocols often assume adversarial nodes in a general term without considering the different types of attacks, which limits transaction throughput at runtime because attacks on liveness could be mitigated. There have been attempts to increase transaction throughput by separately handling the attacks; however, they have security vulnerabilities. This paper introduces Reticulum, a novel...
Mirrored Commitment: Fixing ``Randomized Partial Checking'' and Applications
Paweł Lorek, Moti Yung, Filip Zagórski
Cryptographic protocols
Randomized Partial Checking (RPC} was proposed by Jakobsson, Juels, and Rivest and attracted attention as an efficient method of verifying the correctness of the mixing process in numerous applied scenarios. In fact,
RPC is a building block for many electronic voting schemes, including Prêt à Voter, Civitas, Scantegrity II as well as voting-systems used in real-world elections (e.g., in Australia). Mixing is also used in anonymous transfers of cryptocurrencies.
It turned out, however,...
Election Eligibility with OpenID: Turning Authentication into Transferable Proof of Eligibility
Véronique Cortier, Alexandre Debant, Anselme Goetschmann, Lucca Hirschi
Cryptographic protocols
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...
On Efficient and Secure Compression Modes for Arithmetization-Oriented Hashing
Elena Andreeva, Rishiraj Bhattacharyya, Arnab Roy, Stefano Trevisani
Secret-key cryptography
ZK-SNARKs, a fundamental component of privacy-oriented payment systems, identity protocols, or anonymous voting systems, are advanced cryptographic protocols for verifiable computation: modern SNARKs allow to encode the invariants of a program, expressed as an arithmetic circuit, in an appropriate constraint language from which short, zero-knowledge proofs for correct computations can be constructed.
One of the most important computations that is run through SNARK systems is the...
Security analysis and improvements on a semi-quantum electronic voting protocol
Qiu Shujing, Xin Xiangjun, Zheng Qian, Li Chaoyang, Li Fagen
Cryptographic protocols
Recently, Qiu et al. proposed a semi-quantum voting scheme based on the ring signature (International Journal of Theoretical Physics, 60: 1550–1555(2021)), in which the signer and verifier only need measure the received particles with Z-basis and perform some classical simple encryption/decryption operations on the classical message. Although their scheme is very efficient, it cannot resist against the eavesdropping attacks and forgery attack. In this paper, first, the eavesdropping attacks...
Simple Soundness Proofs
Alex Kampa
Cryptographic protocols
We present a general method to simplify soundness proofs under certain conditions. Given an adversary $\mathcal{A}$ able to break a scheme $S$ with non-negligible probability $t$, we define the concept of $\textit{trace}$ of a $\textit{winning configuration}$, which is already implicitly used in soundness proofs. If a scheme can be constructed that (1) takes a random configuration $e$, being the inputs and execution environment of $\mathcal{A}$, (2) "guesses" a trace, (3) modifies $e$ based...
Camel: E2E Verifiable Instant Runoff Voting without Tallying Authorities
Luke Harrison, Samiran Bag, Feng Hao
Cryptographic protocols
Instant Runoff Voting (IRV) is one example of ranked-choice voting. It provides many known benefits when used in elections, such as minimising vote splitting, ensuring few votes are wasted, and providing resistance to strategic voting. However, the voting and tallying procedures for IRV are much more complicated than those of plurality and are both error-prone and tedious. Many automated systems have been proposed to simplify these procedures in IRV. Some of these also employ cryptographic...
Conan: Distributed Proofs of Compliance for Anonymous Data Collection
Mingxun Zhou, Elaine Shi, Giulia Fanti
Cryptographic protocols
We consider how to design an anonymous data collection protocol that enforces compliance rules.
Imagine that each client contributes multiple data items (e.g., votes, location crumbs, or secret shares of its input) to an anonymous network, which mixes all clients' data items so that the receiver cannot determine which data items belong to the same user. Now, each user must prove to an auditor
that the set it contributed satisfies a compliance predicate, without identifying which items it...
Blockchain Governance via Sharp Anonymous Multisignatures
Wonseok Choi, Xiangyu Liu, Vassilis Zikas
Applications
Electronic voting has occupied a large part of the cryptographic protocols literature. The recent reality of blockchains---in particular their need for online governance mechanisms---has put new parameters and requirements to the problem. We identify the key requirements of a blockchain governance mechanism, namely correctness (including eliminative double votes), voter anonymity, and traceability, and investigate mechanisms that can achieve them with minimal interaction and under...
Thwarting Last-Minute Voter Coercion
Rosario Giustolisi, Maryam Sheikhi Garjan, Carsten Schuermann
Applications
Counter-strategies are key components of coercion-resistant voting schemes, allowing voters to submit votes that represent their own intentions in an environment controlled by a coercer. By deploying a counter-strategy a voter can prevent the coercer from learning if the voter followed the coercer’s instructions or not. Two effective counter-strategies have been proposed in the literature, one based on fake credentials and another on revoting. While fake-credential schemes assume that voters...
Accountable Bulletin Boards: Definition and Provably Secure Implementation
Mike Graf, Ralf Küsters, Daniel Rausch, Simon Egger, Marvin Bechtold, Marcel Flinspach
Foundations
Bulletin boards (BB) are important cryptographic building blocks that, at their core, provide a broadcast channel with
memory. BBs are widely used within many security protocols, including secure multi-party computation protocols, e-voting systems, and electronic auctions. Even though the security of protocols crucially depends on the underlying BB, as also highlighted by recent works, the literature on constructing secure BBs is sparse. The so-far only provably secure BBs require trusted...
Pairing-Free Blind Signatures from Standard Assumptions in the ROM
Julia Kastner, Ky Nguyen, Michael Reichle
Public-key cryptography
Blind Signatures are a useful primitive for privacy preserving applications such as electronic payments, e-voting, anonymous credentials, and more.
However, existing practical blind signature schemes based on standard assumptions require either pairings or lattices. We present the first practical construction of a round-optimal blind signature in the random oracle model based on standard assumptions without resorting to pairings or lattices. In particular, our construction is secure under...
On the Feasibility of E2E Verifiable Online Voting - A Case Study From Durga Puja Trial
Horia Druliac, Matthew Bardsley, Chris Riches, Christian Dunn, Luke Harrison, Bimal Roy, Feng Hao
Applications
India is the largest democracy by population and has one of the largest deployments of e-voting in the world for national elections. However, the e-voting machines used in India are not end-to-end (E2E) verifiable. The inability to verify the tallying integrity of an election by the public leaves the outcome open to disputes. E2E verifiable e-voting systems are commonly regarded as the most promising solution to address this problem, but they had not been implemented or trialed in India. It...
Random Beacons in Monte Carlo: Efficient Asynchronous Random Beacon without Threshold Cryptography
Akhil Bandarupalli, Adithya Bhat, Saurabh Bagchi, Aniket Kate, Michael Reiter
Cryptographic protocols
Regular access to unpredictable and bias-resistant randomness is important for applications such as blockchains, voting, and secure distributed computing. Distributed random beacon protocols address this need by distributing trust across multiple nodes, with the majority of them assumed to be honest. Numerous applications across the blockchain space have led to the proposal of several distributed random beacon protocols, with some already implemented. However, many current random beacon...
Accountability for Misbehavior in Threshold Decryption via Threshold Traitor Tracing
Dan Boneh, Aditi Partap, Lior Rotem
Public-key cryptography
A $t$-out-of-$n$ threshold decryption system assigns key shares to $n$ parties so that any $t$ of them can decrypt a well-formed ciphertext. Existing threshold decryption systems are not secure when these parties are rational actors: an adversary can offer to pay the parties for their key shares. The problem is that a quorum of $t$ parties, working together, can sell the adversary a decryption key that reveals nothing about the identity of the traitor parties. This provides a risk-free...
Deterministic Byzantine Agreement with Adaptive $O(n\cdot f)$ Communication
Fatima Elsheimy, Giorgos Tsimos, Charalampos Papamanthou
Cryptographic protocols
We present a deterministic synchronous protocol for binary Byzantine Agreement against a corrupt minority with adaptive $O(n\cdot f)$ communication complexity, where $f$ is the exact number of corruptions. Our protocol improves the previous best-known deterministic Byzantine Agreement protocol developed by Momose and Ren (DISC 2021), whose communication complexity is quadratic, independent of the exact number of corruptions.
Our approach combines two distinct primitives that we introduce...
Withdrawable Signature: How to Call off a Signature
Xin Liu, Joonsang Baek, Willy Susilo
Public-key cryptography
Digital signatures are a cornerstone of security and trust in cryptography, providing authenticity, integrity, and non-repudiation. Despite their benefits, traditional digital signature schemes suffer from inherent immutability, offering no provision for a signer to retract a previously issued signature. This paper introduces the concept of a withdrawable signature scheme, which allows for the retraction of a signature without revealing the signer's private key or compromising the security...
DeVoS: Deniable Yet Verifiable Vote Updating
Johannes Mueller, Balazs Pejo, Ivan Pryvalov
Cryptographic protocols
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...
A Scalable Coercion-resistant Voting Scheme for Blockchain Decision-making
Zeyuan Yin, Bingsheng Zhang, Andrii Nastenko, Roman Oliynykov, Kui Ren
Cryptographic protocols
Typically, a decentralized collaborative blockchain decision-making mechanism is realized by remote voting. To date, a number of blockchain voting schemes have been proposed; however, to the best of our knowledge, none of these schemes achieve coercion-resistance. In particular, for most blockchain voting schemes, the randomness used by the voting client can be viewed as a witness/proof of the actual vote, which enables improper behaviors such as coercion and vote-buying. Unfortunately, the...
Efficient and Usable Coercion-Resistant E-Voting on the Blockchain
Neyire Deniz Sarier
Applications
In [1], Sarier presents a practical biometric-based non-transferable credential scheme that maintains the efficiency of the underlying Brands credential. In this paper, we design a new Blockchain-Based E-Voting (BBEV) scheme that combines the system of [1] with encrypted Attribute Based Credentials for a non-transferable code-voting approach to achieve efficient, usable, anonymous, transparent, auditable, verifiable, receipt-free and coercion-resistant remote voting system for small/medium...
Linearly-Homomorphic Signatures for Short Randomizable Proofs of Subset Membership
David Pointcheval
Cryptographic protocols
Electronic voting is one of the most interesting application of modern cryptography, as it involves many innovative tools (such as homomorphic public-key encryption, non-interactive zero-knowledge proofs, and distributed cryptography) to guarantee several a priori contradictory security properties: the integrity of the tally and the privacy of the individual votes. While many efficient solutions exist for honest-but-curious voters, that follow the official procedure but try to learn more...
Cicada: A framework for private non-interactive on-chain auctions and voting
Noemi Glaeser, István András Seres, Michael Zhu, Joseph Bonneau
Cryptographic protocols
Auction and voting schemes play a crucial role in the Web3 ecosystem. Yet currently deployed implementations either lack privacy or require at least two rounds, hindering usability and security. We introduce Cicada, a general framework for using linearly homomorphic time-lock puzzles (HTLPs) to enable provably secure, non-interactive private auction and voting protocols. We instantiate our framework with an efficient new HTLP construction and novel packing techniques that enable succinct...
OpenVoting: Recoverability from Failures in Dual Voting
Prashant Agrawal, Kabir Tomer, Abhinav Nakarmi, Mahabir Prasad Jhanwar, Subodh Sharma, Subhashis Banerjee
Applications
In this paper we address the problem of recovery from failures without re-running entire elections when elections fail to verify. We consider the setting of $\textit{dual voting}$ protocols, where the cryptographic guarantees of end-to-end verifiable voting (E2E-V) are combined with the simplicity of audit using voter-verified paper records (VVPR). We first consider the design requirements of such a system and then suggest a protocol called $\textit{OpenVoting}$, which identifies a...
Fully Tally-Hiding Verifiable E-Voting for Real-World Elections with Seat-Allocations
Carmen Wabartha, Julian Liedtke, Nicolas Huber, Daniel Rausch, Ralf Kuesters
Cryptographic protocols
Modern e-voting systems provide what is called verifiability, i.e., voters are able to check that their votes have actually been counted despite potentially malicious servers and voting authorities. Some of these systems, called tally-hiding systems, provide increased privacy by revealing only the actual election result, e.g., the winner of the election, but no further information that is supposed to be kept secret. However, due to these very strong privacy guarantees, supporting complex...
Optimal Flexible Consensus and its Application to Ethereum
Joachim Neu, Srivatsan Sridhar, Lei Yang, David Tse
Cryptographic protocols
Classic BFT consensus protocols guarantee safety and liveness for all clients if fewer than one-third of replicas are faulty. However, in applications such as high-value payments, some clients may want to prioritize safety over liveness. Flexible consensus allows each client to opt for a higher safety resilience, albeit at the expense of reduced liveness resilience. We present the first construction that allows optimal safety-liveness tradeoff for every client simultaneously. This...
DualDory: Logarithmic-Verifier Linkable Ring Signatures through Preprocessing
Jonathan Bootle, Kaoutar Elkhiyaoui, Julia Hesse, Yacov Manevich
Public-key cryptography
A linkable ring signature allows a user to sign anonymously on behalf of a group while ensuring that multiple signatures from the same user are detected. Applications such as privacy-preserving e-voting and e-cash can leverage linkable ring signatures to significantly improve privacy and anonymity guarantees. To scale to systems involving large numbers of users, short signatures with fast verification are a must. Concretely efficient ring signatures currently rely on a trusted authority...
Practically-exploitable Vulnerabilities in the Jitsi Video Conferencing System
Robertas Maleckas, Kenneth G. Paterson, Martin R. Albrecht
Attacks and cryptanalysis
Jitsi Meet is an open-source video conferencing system, and a popular alternative to proprietary services such as Zoom and Google Meet. The Jitsi project makes strong privacy and security claims in its advertising, but there is no published research into the merits of these claims. Moreover, Jitsi announced end-to-end encryption (E2EE) support in April 2020, and prominently features this in its marketing.
We present an in-depth analysis of the design of Jitsi and its use of cryptography....
Tornado Vote: Anonymous Blockchain-Based Voting
Robert Muth, Florian Tschorsch
Applications
Decentralized apps (DApps) often hold significant cryptocurrency assets. In order to manage these assets and coordinate joint investments, shareholders leverage the underlying smart contract functionality to realize a transparent, verifiable, and secure decision-making process. That is, DApps implement proposal-based voting. Permissionless blockchains, however, lead to a conflict between transparency and anonymity; potentially preventing free decision-making if individual votes and...
Coercion Mitigation for Voting Systems with Trackers: A Selene Case Study
Kristian Gjøsteen, Thomas Haines, Morten Rotvold Solberg
Cryptographic protocols
An interesting approach to achieving verifiability in voting systems is to make use of tracking numbers. This gives voters a simple way of verifying that their ballot was counted: they can simply look up their ballot/tracker pair on a public bulletin board. It is crucial to understand how trackers affect other security properties, in particular privacy. However, existing privacy definitions are not designed to accommodate tracker-based voting systems. Furthermore, the addition of trackers...
Tiresias: Large Scale, Maliciously Secure Threshold Paillier
Offir Friedman, Avichai Marmor, Dolev Mutzari, Yehonatan C. Scaly, Yuval Spiizer, Avishay Yanai
Cryptographic protocols
In the threshold version of Paillier's encryption scheme, a set of parties collectively holds the secret decryption key through a secret sharing scheme.
Whenever a ciphertext is to be decrypted, the parties send their decryption shares, which are then verified for correctness and combined into the plaintext.
The scheme has been widely adopted in various applications, from secure voting to general purpose MPC protocols.
However, among the handful existing proposals for a maliciously...
More Efficient Post-Quantum Electronic Voting from NTRU
Patrick Hough, Caroline Sandsbråten, Tjerand Silde
Cryptographic protocols
In recent years, there has been much focus on developing core cryptographic primitives based on lattice assumptions, driven by the NIST cal for post-quantum key encapsulation and digital signature algorithms. However, more work must be conducted on efficient privacy-preserving protocols with post-quantum security.
Electronic voting is one such privacy-preserving protocol whose adoption is increasing across the democratic world. E-voting offers both a fast and convenient alternative to...
Faster coercion-resistant e-voting by encrypted sorting
Diego F. Aranha, Michele Battagliola, Lawrence Roy
Applications
Coercion-resistance is one of the most challenging security properties to achieve when designing an e-voting protocol. The JCJ voting scheme, proposed in 2005 by Juels, Catalano and Jakobsson, is one of the first voting systems where coercion-resistance was rigorously defined and achieved, making JCJ the benchmark for coercion-resistant protocols. Recently, the coercion-resistance definition proposed in JCJ has been disputed and improved by Cortier, Gaudry, and Yang. They identified a major...
The Referendum Problem in Anonymous Voting for Decentralized Autonomous Organizations
Artem Grigor, Vincenzo Iovino, Giuseppe Visconti
Applications
A natural approach to anonymous voting over Ethereum assumes that there is an off-chain aggregator that performs the following task. The aggregator receives valid signatures of YES/NO preferences from eligible voters and uses them to compute a zk-SNARK proof of the fact that the majority of voters have cast a preference for YES or NO. Then, the aggregator sends to the smart contract the zk-SNARK proof, the smart contract verifies the proof and can trigger an action (e.g., a transfer of...
VeriVoting: A decentralized, verifiable and privacy-preserving scheme for weighted voting
Xiaohan Yue
Cryptographic protocols
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...
2023/667
Last updated: 2023-09-18
New Bounds on the Accuracy of Majority Voting for Multi-Class Classification
Sina Aeeneh
Foundations
Majority voting is a simple mathematical function that returns the value that appears most often in a set. As a popular decision fusion technique, the majority voting function (MVF) finds applications in resolving conflicts, where a number of independent voters report their opinions on a classification problem. Despite its importance and its various applications in ensemble learning, data crowd-sourcing, remote sensing, and data oracles for blockchains, the accuracy of the MVF for the...
On the Security of Blind Signatures in the Multi-Signer Setting
Samuel Bedassa Alemu, Julia Kastner
Public-key cryptography
Blind signatures were originally introduced by Chaum (CRYPTO ’82) in the context of privacy-preserving electronic payment systems. Nowadays, the cryptographic primitive has also found applications in anonymous credentials and voting systems. However, many practical blind signature schemes have only been analysed in the game-based setting where a single signer is present. This is somewhat unsatisfactory as blind signatures are intended to be deployed in a setting with many signers. We address...
Ruffle: Rapid 3-party shuffle protocols
Pranav Shriram A, Nishat Koti, Varsha Bhat Kukkala, Arpita Patra, Bhavish Raj Gopal, Somya Sangal
Cryptographic protocols
Secure shuffle is an important primitive that finds use in several applications such as secure electronic voting, oblivious RAMs, secure sorting, to name a few. For time-sensitive shuffle-based applications that demand a fast response time, it is essential to design a fast and efficient shuffle protocol. In this work, we design secure and fast shuffle protocols relying on the techniques of secure multiparty computation. We make several design choices that aid in achieving highly efficient...
Game Theoretical Analysis of DAG-Ledgers Backbone
Yackolley Amoussou-Guenou, Simone Galimberti, Maria Potop-Butucaru
Foundations
We study the rational behaviors of agents in DAG-Based Distributed Ledgers. We an-
alyze generic algorithms that encapsulate the main actions of agents in a DAG-based dis-
tributed ledger: voting for a block, and checking its validity. Knowing that those actions
have costs, and validating a block gives rewards to agents who participated in the validation
procedure, we study using game theory how strategic agents behave while trying to maximize
their gains. We consider scenarios with...
Composable Long-Term Security with Rewinding
Robin Berger, Brandon Broadnax, Michael Klooß, Jeremias Mechler, Jörn Müller-Quade, Astrid Ottenhues, Markus Raiber
Foundations
Long-term security, a variant of Universally Composable (UC) security introduced by Müller-Quade and Unruh (JoC ’10), allows to analyze the security of protocols in a setting where all hardness assumptions no longer hold after the protocol execution has finished. Such a strict notion is highly desirable when properties such as input privacy need to be guaranteed for a long time, e.g. zero-knowledge proofs for secure electronic voting. Strong impossibility results rule out so-called...
A Novel Approach to e-Voting with Group Identity Based Identification and Homomorphic Encryption
Apurva K Vangujar, Buvana Ganesh, Alia Umrani, Paolo Palmieri
Public-key cryptography
This paper presents a novel e-voting scheme that combines Group Identity-based Identification (GIBI) with Homomorphic Encryption (HE) based on the discrete logarithmic assumption. The proposed scheme uses the Schnorr-like GIBI scheme for voter identification and authorization using Zero-Knowledge (ZK) proof to ensure the anonymity and eligibility of voters. The use of Distributed ElGamal (DE) provides fairness and receipt-freeness, while the use of partial shares for decryption enables...
Reputation-based state machine replication
Muhong Huang, Runchao Han, Zhiqiang Du, Yanfang Fu, Liangxin Liu
Cryptographic protocols
State machine replication (SMR) allows nodes to
jointly maintain a consistent ledger, even when a part of nodes
are Byzantine. To defend against and/or limit the impact of
attacks launched by Byzantine nodes, there have been proposals
that combine reputation mechanisms to SMR, where each node
has a reputation value based on its historical behaviours, and
the node’s voting power will be proportional to its reputation.
Despite the promising features of reputation-based SMR,...
Practically optimizing multi-dimensional discrete logarithm calculations: Implementations in subgroups of $\mathbb{Z}^{*}_{p}$ relevant to electronic voting and cash schemes
Madhurima Mukhopadhyay
Public-key cryptography
Discrete logarithm problem(DLP) is the pillar of many cryptographical schemes. We propose an
improvement to the Gaudry-Schost algorithm, for multi-dimensional DLP. We have derived the cost
estimates in general and specialized cases, which prove efficiency of our new method. We report
the implementation of our algorithm, which confirms the theory. Both theory and experiments val-
idate the fact that the advantage of our algorithm increases for large sizes, which helps in...
2023/131
Last updated: 2023-03-22
Some Practical Applications of Fully Homomorphic Encryption
Elisa Giurgea, Tudor Hutu, Emil Simion
Foundations
In the current context of the increasing need for data privacy and quantum computing no longer being just a novel concept, Fully Homomorphic Encryption presents us with numerous quantum-secure schemes which have the concept of enabling data processing over encrypted data while not decrypting it behind. While not entirely usable at the present time, recent research has underlined its practical uses applied to databases, cloud computing, machine learning, e-voting, and IoT computing. In this...
An analysis of a scheme proposed for electronic voting systems
Nicu Neculache, Vlad-Andrei Petcu, Emil Simion
Cryptographic protocols
Voting mechanisms allow the expression of the elections by a democratic approach. Any voting scheme must ensure, preferably in an efficient way, a series of safety measures such as confidentiality, integrity and anonymity. Since the 1980s, the concept of electronic voting became more and more of interest, being an advantageous or even necessary alternative for the organization of secure elections. In this paper, we give an overview for the e-voting mechanisms together with the security...
Complete Knowledge: Preventing Encumbrance of Cryptographic Secrets
Mahimna Kelkar, Kushal Babel, Philip Daian, James Austgen, Vitalik Buterin, Ari Juels
Most cryptographic protocols model a player’s knowledge of secrets in a simple way. Informally, the player knows a secret in the sense that she can directly furnish it as a (private) input to a protocol, e.g., to digitally sign a message.
The growing availability of Trusted Execution Environments (TEEs) and secure multiparty computation, however, undermines this model of knowledge. Such tools can encumber a secret sk and permit a chosen player to access sk conditionally, without actually...
On blindness of several ElGamal-type blind signatures
Alexandra Babueva, Liliya Akhmetzyanova, Evgeny Alekseev, Oleg Taraskin
Public-key cryptography
Blind signature schemes are the essential element of many complex information systems such as e-cash and e-voting systems. They should provide two security properties: unforgeability and blindness. The former one is standard for all signature schemes and ensures that a valid signature can be generated only during the interaction with the secret signing key holder. The latter one is more specific for this class of signature schemes and means that there is no way to link a (message, signature)...
Practical Quantum-Safe Voting from Lattices, Extended
Ian Black, Emma McFall, Juliet Whidden, Bryant Xie, Ryann Cartor
Public-key cryptography
E-voting offers significant potential savings in time and money compared to current voting systems. Unfortunately, many current e-voting schemes are susceptible to quantum attacks. In this paper, we expand upon EVOLVE, an existing lattice-based quantum-secure election scheme introduced by Pino et al. We are able to make these expansions by extending the dimensions of the voter's ballot and creating additional proofs, allowing for applicability to realistic election schemes. Thus, we present...
Reversing, Breaking, and Fixing the French Legislative Election E-Voting Protocol
Alexandre Debant, Lucca Hirschi
Attacks and cryptanalysis
We conduct a security analysis of the e-voting protocol used for the largest political election using e-voting in the world, the 2022 French legislative election for the citizens overseas. Due to a lack of system and threat model specifications, we built and contributed such specifications by studying the French legal framework and by reverse-engineering the code base accessible to the voters. Our analysis reveals that this protocol is affected by two design-level and implementation-level...
sVote with Control Components Voting Protocol. Computational Proof of Complete Verifiability and Privacy.
Enrique Larraia, Tamara Finogina, Nuria Costa
Cryptographic protocols
This document details the cryptographic analysis of the sVote v2.2.1 system - an e-voting solution developed by Scytl for the Switzerland context. We prove the complete verifiability and privacy under the Swiss legislation's informally stated goals.
First, we derive the trust model for complete verifiability and voting secrecy from the Swiss Chancellery's requirements [1][2], supporting our interpretation by quotes from and references to relevant excerpts of the ordinance and the...
Eagle: Efficient Privacy Preserving Smart Contracts
Carsten Baum, James Hsin-yu Chiang, Bernardo David, Tore Kasper Frederiksen
Cryptographic protocols
The proliferation of Decentralised Finance (DeFi) and Decentralised Autonomous Organisations (DAO), which in current form are exposed to front-running of token transactions and proposal voting, demonstrate the need to shield user inputs and internal state from the parties executing smart contracts. In this work we present “Eagle”, an efficient UC-secure protocol which efficiently realises a notion of privacy preserving smart contracts where both the amounts of tokens and the auxiliary data...
The Abe-Okamoto Partially Blind Signature Scheme Revisited
Julia Kastner, Julian Loss, Jiayu Xu
Public-key cryptography
Partially blind signatures, an extension of ordinary blind signatures, are a primitive with wide applications in e-cash and electronic voting. One of the most efficient schemes to date is the one by Abe and Okamoto (CRYPTO 2000), whose underlying idea - the OR-proof technique - has served as the basis for several works.
We point out several subtle flaws in the original proof of security, and provide a new detailed and rigorous proof, achieving similar bounds as the original work. We...
VoteXX: A Solution to Improper Influence in Voter-Verifiable Elections
David Chaum, Richard T. Carback, Jeremy Clark, Chao Liu, Mahdi Nejadgholi, Bart Preneel, Alan T. Sherman, Mario Yaksetig, Zeyuan Yin, Filip Zagórski, Bingsheng Zhang
Cryptographic protocols
We solve a long-standing challenge to the integrity of votes cast without the supervision of a voting booth: “improper influence,” which we define as any combination of vote buying and voter coercion. Our approach allows each voter, or their trusted agent(s), to cancel their vote in a way that is unstoppable, irrevocable, and forever unattributable to the voter. In particular, our approach enhances security of online, remote, public-sector elections, for which there is a growing need and the...
Machine-Checked Proofs of Privacy Against Malicious Boards for Selene & Co
Constantin Cătălin Drăgan, François Dupressoir, Ehsan Estaji, Kristian Gjøsteen, Thomas Haines, Peter Y. A. Ryan, Peter B. Rønne, Morten Rotvold Solberg
Cryptographic protocols
Privacy is a notoriously difficult property to achieve in complicated systems and especially in electronic voting schemes. Moreover, electronic voting schemes is a class of systems that require very high assurance. The literature contains a number of ballot privacy definitions along with security proofs for common systems. Some machine-checked security proofs have also appeared. We define a new ballot privacy notion that captures a larger class of voting schemes. This notion improves on the...
Kryvos: Publicly Tally-Hiding Verifiable E-Voting
Nicolas Huber, Ralf Kuesters, Toomas Krips, Julian Liedtke, Johannes Mueller, Daniel Rausch, Pascal Reisert, Andreas Vogt
Cryptographic protocols
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...
Efficient Unique Ring Signatures From Lattices
Tuong Ngoc Nguyen, Anh The Ta, Huy Quoc Le, Dung Hoang Duong, Willy Susilo, Fuchun Guo, Kazuhide Fukushima, Shinsaku Kiyomoto
Cryptographic protocols
Unique ring signatures (URS) were introduced by Franklin and Zhang (FC 2012) as a unification of linkable and traceable ring signatures. In URS, each member within a ring can only produce, on behalf of the ring, at most one signature for a message. Applications of URS potentially are e-voting systems and e–token systems. In blockchain technology, URS has been implemented for mixing contracts. However, existing URS schemes are based on the Discrete Logarithm Problem, which is insecure in the...
How to Verifiably Encrypt Many Bits for an Election?
Henri Devillez, Olivier Pereira, Thomas Peters
Public-key cryptography
The verifiable encryption of bits is the main computational step that is needed to prepare ballots in many practical voting protocols. Its computational load can also be a practical bottleneck, preventing the deployment of some protocols or requiring the use of computing clusters.
We investigate the question of producing many verifiably encrypted bits in an efficient and portable way, using as a baseline the protocol that is in use in essentially all modern voting systems and libraries...
Statistical Decoding 2.0: Reducing Decoding to LPN
Kevin Carrier, Thomas Debris-Alazard, Charles Meyer-Hilfiger, Jean-Pierre Tillich
Attacks and cryptanalysis
The security of code-based cryptography relies primarily on the hardness of generic decoding with linear codes. The best generic decoding algorithms are all improvements of an old algorithm due to Prange: they are known under the name of information set decoders (ISD).
A while ago, a generic decoding algorithm which does not belong to this family was proposed: statistical decoding.
It is a randomized algorithm that requires the computation of a large set of parity-checks of moderate...
Scan, Shuffle, Rescan: Machine-Assisted Election Audits With Untrusted Scanners
Douglas W. Jones, Sunoo Park, Ronald L. Rivest, Adam Sealfon
Applications
We introduce a new way to conduct election audits using untrusted scanners. Post-election audits perform statistical hypothesis testing to confirm election outcomes. However, existing approaches are costly and laborious for close elections---often the most important cases to audit---requiring extensive hand inspection of ballots. We instead propose automated consistency checks, augmented by manual checks of only a small number of ballots. Our protocols scan each ballot twice, shuffling the...
A New Approach to the Constant-Round Re-encryption Mix-Net
Myungsun Kim
Cryptographic protocols
The re-encryption mix-net (RMN) is a basic cryptographic tool that is widely used in the privacy protection domain and requires anonymity support; for example, it is used in electronic voting, web browsing, and location systems. To protect information about the relationship between senders and messages, a number of mix servers in RMNs shuffle and forward a list of input ciphertexts in a cascading manner. The output of the last mix server is decrypted to yield the set of original messages....
Traceable Receipt-Free Encryption
Henri Devillez, Olivier Pereira, Thomas Peters
Public-key cryptography
CCA-like game-based security definitions capture confidentiality by asking an adversary to distinguish between honestly computed encryptions of chosen plaintexts. In the context of voting systems, such guarantees have been shown to be sufficient to prove ballot privacy (Asiacrypt'12).
In this paper, we observe that they fall short when one seeks to obtain receipt-freeness, that is, when corrupted voters who submit chosen ciphertexts encrypting their vote must be prevented from proving...
Privacy Preserving Opinion Aggregation
Aggelos Kiayias, Vanessa Teague, Orfeas Stefanos Thyfronitis Litos
Cryptographic protocols
There are numerous settings in which people's preferences are aggregated outside of formal elections, and where privacy and verification are important but the stringent authentication and coercion-resistant properties of government elections do not apply, a prime example being social media platforms. These systems are often iterative and have no trusted authority, in contrast to the centrally organised, single-shot elections on which most of the literature is focused. Moreover, they require...
How Efficient are Replay Attacks against Vote Privacy? A Formal Quantitative Analysis
David Mestel, Johannes Mueller, Pascal Reisert
Foundations
Replay attacks are among the most well-known attacks against vote privacy. Many e-voting systems have been proven vulnerable to replay attacks, including systems like Helios that are used in real practical elections.
Despite their popularity, it is commonly believed that replay attacks are inefficient but the actual threat that they pose to vote privacy has never been studied formally. Therefore, in this paper, we precisely analyze for the first time how efficient replay attacks really...
Find the Bad Apples: An efficient method for perfect key recovery under imperfect SCA oracles – A case study of Kyber
Muyan Shen, Chi Cheng, Xiaohan Zhang, Qian Guo, Tao Jiang
Public-key cryptography
Side-channel resilience is a crucial feature when assessing whether a post-quantum cryptographic proposal is sufficiently mature to be deployed. In this paper, we propose a generic and efficient adaptive approach to improve the sample complexity (i.e., the required number of traces) of plaintext-checking (PC) oracle-based side-channel attacks (SCAs), a major class of key recovery chosen-ciphertext SCAs on lattice-based key encapsulation mechanisms. This new approach is preferable when the...
Aura: private voting with reduced trust on tallying authorities
Aram Jivanyan, Aaron Feickert
Applications
Electronic voting has long been an area of active and challenging research. Security properties relevant to physical voting in elections with a variety of threat models and priorities are often difficult to reproduce in cryptographic systems and protocols. Existing work in this space often focuses on the privacy of ballot contents, assurances to voters that their votes are tabulated, and verification that election results are correct; however, privacy of voter identity is often offloaded to...
Publicly Accountable Robust Multi-Party Computation
Marc Rivinius, Pascal Reisert, Daniel Rausch, Ralf Kuesters
Cryptographic protocols
In recent years, lattice-based secure multi-party computation (MPC) has seen a rise in popularity and is used more and more in large scale applications like privacy-preserving cloud computing, electronic voting, or auctions. Many of these applications come with the following high security requirements: a computation result should be publicly verifiable, with everyone being able to identify a malicious party and hold it accountable, and a malicious party should not be able to corrupt the...
Is the JCJ voting system really coercion-resistant?
Véronique Cortier, Pierrick Gaudry, Quentin Yang
Cryptographic protocols
Coercion-resistance is a security property of electronic voting, often considered as a must-have for high-stake elections. The JCJ voting scheme, proposed in 2005 by Juels, Catalano and Jakobsson, is still the reference paradigm when designing a coercion-resistant protocol. We highlight a weakness in JCJ that is also present in all the systems following its general structure. This comes from the procedure that precedes the tally, where the trustees remove the ballots that should not be...
Verifiable Mix-Nets and Distributed Decryption for Voting from Lattice-Based Assumptions
Diego F. Aranha, Carsten Baum, Kristian Gjøsteen, Tjerand Silde
Cryptographic protocols
Cryptographic voting protocols have recently seen much interest from practitioners due to their (planned) use in countries such as Estonia, Switzerland, France, and Australia. Practical protocols usually rely on tested designs such as the mixing-and-decryption paradigm. There, multiple servers verifiably shuffle encrypted ballots, which are then decrypted in a distributed manner. While several efficient protocols implementing this paradigm exist from discrete log-type assumptions, the...
2022/391
Last updated: 2022-06-01
An Improved Model on the Vague Sets-Based DPoS’s Voting Phase in Blockchain
Lin You, Zhuobiao Wang, Gengran Hu, Chengtang Cao
As a common consensus mechanism used in blockchain systems, DPoS uses voting to select committee members who will generate the corresponding blocks. In order to elect committee members as fairly as possible, the vague sets are introduced into the voting phase of DPoS. In the vague sets based model proposed by Xu et al., the voting nodes can vote for, oppose or abstain from it. In this paper, we improve this vague set based model by introducing a new mapping from the vague set to fuzzy
set...
Blind accumulators for e-voting
Sergey Agievich
Public-key cryptography
We present a novel cryptographic primitive, blind accumulator, aimed at constructing e-voting systems. Blind accumulators collect private keys of eligible voters in a decentralized manner not getting information about the keys. Once the accumulation is complete, a voter processes the resulting accumulator deriving a public key that refers to the private key previously added by this voter. Public keys are derived deterministically and can therefore stand as fixed voter pseudonyms. The voter...
Dispute-free Scalable Open Vote Network using zk-SNARKs
Muhammad ElSheikh, Amr M. Youssef
Applications
The Open Vote Network is a self-tallying decentralized e-voting protocol suitable for boardroom elections. Currently, it has two Ethereum-based implementations: the first, by McCorry et al., has a scalability issue since all the computations are performed on-chain. The second implementation, by Seifelnasr et al., solves this issue partially by assigning a part of the heavy computations to an off-chain untrusted administrator in a verifiable manner. As a side effect, this second...
Surveying definitions of election verifiability
Ben Smyth, Michael R. Clarkson
Foundations
We explore definitions of verifiability by Juels et al. (2010), Cortier et al. (2014), and Kiayias et al. (2015). We discover that voting systems vulnerable to attacks can be proven to satisfy each of those definitions and conclude they are unsuitable for the analysis of voting systems. Our results will fuel the exploration for a new definition.
Half-Aggregation of Schnorr Signatures with Tight Reductions
Yanbo Chen, Yunlei Zhao
Public-key cryptography
An aggregate signature (AS) scheme allows an unspecified aggregator to compress many signatures into a short aggregation. AS schemes can save storage costs and accelerate verification. They are desirable for applications where many signatures need to be stored, transferred, or verified together, like blockchain systems, network routing, e-voting, and certificate chains. However, constructing AS schemes based on general groups, only requiring the hardness of the discrete logarithm problem, is...
OptRand: Optimistically responsive distributed random beacons
Adithya Bhat, Nibesh Shrestha, Aniket Kate, Kartik Nayak
Cryptographic protocols
Public random beacons publish random numbers at regular intervals, which anyone can obtain and verify. The design of public distributed random beacons has been an exciting research direction with significant implications for blockchains, voting, and beyond. Distributed random beacons, in addition to being bias-resistant and unpredictable, also need to have low communication overhead and latency, high resilience to faults, and ease of reconfigurability. Existing synchronous random beacon...
RLWE-based distributed key generation and threshold decryption
Ferran Alborch, Ramiro Martínez, Paz Morillo
Public-key cryptography
Ever since the appearance of quantum computers, prime factoring and discrete logarithm based cryptography has been put in question, giving birth to the so called post-quantum cryptography. The most prominent field in post-quantum cryptography is lattice-based cryptography, protocols that are proved to be as difficult to break as certain difficult lattice problems like Learning With Errors (LWE) or Ring Learning With Errors (RLWE). Furthermore, the application of cryptographic techniques to...
Efficient and Post-Quantum Zero-Knowledge Proofs for Blockchain Confidential Transaction Protocols
Shang GAO, Tianyu ZHENG, Yu GUO, Bin XIAO
Cryptographic protocols
We propose new zero-knowledge proofs for efficient and post-quantum ring confidential transaction (RingCT) protocols based on lattice assumptions in Blockchain systems. First, we introduce an inner-product based linear equation satisfiability approach for balance proofs with a wide range (e.g. 64-bit precision). Unlike existing balance proofs that require additional proofs for some ''corrector values'' [CCS'19], our approach avoids the corrector values for better efficiency. Furthermore, we...
Relations between Privacy, Verifiability, Accountability and Coercion-Resistance in Voting Protocols
Alisa Pankova, Jan Willemson
Cryptographic protocols
This paper studies quantitative relationships between privacy, verifiability, accountability, and coercion-resistance of voting protocols. We adapt existing definitions to make them better comparable with each other and determine which bounds a certain requirement on one property poses on some other property. It turns out that, in terms of proposed definitions, verifiability and accountability do not necessarily put constraints on privacy and coercion-resistance. However, the relations...
Improved Lattice-Based Mix-Nets for Electronic Voting
Valeh Farzaliyev, Jan Willemson, Jaan Kristjan Kaasik
Public-key cryptography
Mix-networks were first proposed by Chaum in the late 1970s -- early 1980s as a general tool for building anonymous communication systems. Classical mix-net implementations rely on standard public key primitives (e.g. ElGamal encryption) that will become vulnerable when a sufficiently powerful quantum computer will be built. Thus, there is a need to develop quantum-resistant mix-nets. This paper focuses on the application case of electronic voting where the number of votes to be mixed may...
Russian Federal Remote E-voting Scheme of 2021 -- Protocol Description and Analysis
Jelizaveta Vakarjuk, Nikita Snetkov, Jan Willemson
Applications
This paper presents the details of one of the two cryptographic remote e-voting protocols used in the Russian parliamentary elections of 2021. As the official full version of the scheme has never been published by the election organisers, our paper aims at putting together as complete picture as possible from various incomplete sources. As all the currently available sources are in Russian, our presentation also aims at serving the international community by making the description available...
Extending the Tally-Hiding Ordinos System: Implementations for Borda, Hare-Niemeyer, Condorcet, and Instant-Runoff Voting
Fabian Hertel, Nicolas Huber, Jonas Kittelberger, Ralf Kuesters, Julian Liedtke, Daniel Rausch
Cryptographic protocols
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...
Generalized Proof of Liabilities
Yan Ji, Konstantinos Chalkias
Cryptographic protocols
Proof of liabilities (PoL) allows a prover to prove his/her liabilities to a group of verifiers. This is a cryptographic primitive once used only for proving financial solvency but is also applicable to domains outside finance, including transparent and private donations, new algorithms for disapproval voting and publicly verifiable official reports such as COVID-19 daily cases. These applications share a common nature in incentives: it's not in the prover's interest to increase his/her...
Shuffling Public Keys (A Peer-to-peer Voting Algorithm)
Santi J. Vives
Public-key cryptography
A peer-to-peer, permissionless, and distributed cryptographic voting system that relies only on the existence of generic digital signatures and encryption.
Count Me In! Extendability for Threshold Ring Signatures
Diego F. Aranha, Mathias Hall-Andersen, Anca Nitulescu, Elena Pagnin, Sophia Yakoubov
Cryptographic protocols
Ring signatures enable a signer to sign a message on behalf of a group anonymously, without revealing her identity. Similarly, threshold ring signatures allow several signers to sign the same message on behalf of a group; while the combined signature reveals that some threshold $t$ of the group members signed the message, it does not leak anything else about the signers' identities.
Anonymity is a central feature in threshold ring signature applications, such as whistleblowing, e-voting...
We present Hyperion, an end-to-end verifiable e-voting scheme that allows the voters to identify their votes in cleartext in the final tally. In contrast to schemes like Selene or sElect, identification is not via (private) tracker numbers but via cryptographic commitment terms. After publishing the tally, the Election Authority provides each voter with an individual dual key. Voters identify their votes by raising their dual key to their secret trapdoor key and finding the matching...
As a prominent category of side-channel attacks (SCAs), plaintext-checking (PC) oracle-based SCAs offer the advantages of generality and operational simplicity on a targeted device. At TCHES 2023, Rajendran et al. and Tanaka et al. independently proposed the multiple-valued (MV) PC oracle, significantly reducing the required number of queries (a.k.a., traces) in the PC oracle. However, in practice, when dealing with environmental noise or inaccuracies in the waveform classifier, they...
Coercion is a challenging and multi-faceted threat that prevents people from expressing their will freely. Similarly, vote-buying does to undermine the foundation of free democratic elections. These threats are especially dire for remote electronic voting, which relies on voters to express their political will freely but happens in an uncontrolled environment outside the polling station and the protection of the ballot booth. However, electronic voting in general, both in-booth and remote,...
Traceable Receipt-free Encryption (TREnc) is a verifiable public-key encryption primitive introduced at Asiacrypt 2022. A TREnc allows randomizing ciphertexts in transit in order to remove any subliminal information up to a public trace that ensures the non-malleability of the underlying plaintext. A remarkable property of TREnc is the indistinguishability of the randomization of chosen ciphertexts against traceable chosen-ciphertext attacks (TCCA). This property can support applications...
Blockchain consensus, a.k.a. BFT SMR, are protocols enabling $n$ processes to decide on an ever-growing chain. The fastest known asynchronous one is called 2-chain VABA (PODC'21 and FC'22), and is used as fallback chain in Abraxas* (CCS'23). It has a claimed $9.5\delta$ expected latency when used for a single shot instance, a.k.a. an MVBA. We exhibit attacks breaking it. Hence, the title of the fastest asynchronous MVBA with quadratic messages complexity goes to sMVBA (CCS'22), with...
Zero-knowledge shuffle arguments are a useful tool for constructing mix-nets which enable anonymous communication. We propose a new shuffle argument using a novel technique that probabilistically checks that each weighted set of input elements corresponds to some weighted set of output elements, with weights from the same set as the input element weights. We achieve this using standard discrete log assumptions and the shortest integer solution (SIS) assumption. Our shuffle argument has...
PeaceFounder is a centralised E2E verifiable e-voting system that leverages pseudonym braiding and history trees. The immutability of the bulletin board is maintained replication-free by voter’s client devices with locally stored consistency-proof chains. Meanwhile, pseudonym braiding done via an exponentiation mix before the vote allows anonymisation to be transactional with a single braider at a time. In contrast to existing E2E verifiable e-voting systems, it is much easier to deploy as...
To securely transmit sensitive information into the future, Time-Lock Puzzles (TLPs) have been developed. Their applications include scheduled payments, timed commitments, e-voting, and sealed-bid auctions. Homomorphic TLP is a key variant of TLP that enables computation on puzzles from different clients. This allows a solver/server to tackle only a single puzzle encoding the computation's result. However, existing homomorphic TLPs lack support for verifying the correctness of the...
We introduce ${zkVoting}$, a coercion-resistant e-voting system that utilizes a fake keys approach based on a novel nullifiable commitment scheme. This scheme allows voters to receive both real and fake commitment keys from a registrar. Each ballot includes this commitment, but only the tallier can efficiently discern the fake ballots, simplifying the tally process to $\mathcal{O}(n)$ and ensuring coercion resistance. ${zkVoting}$ also preserves voter anonymity by ensuring each ballot...
t-out-of-n threshold ring signature (TRS) is a type of anonymous signature designed for t signers to jointly sign a message while hiding their identities among n parties that include themselves. However, can TRS address those needs if one of the signers wants to revoke his signature or, additively, sign separately later? Can non-signers be revoked without compromising anonymity? Previous research has only discussed opposing situations. The present study introduces a novel property for...
ElectionGuard is a flexible set of open-source tools that---when used with traditional election systems---can produce end-to-end verifiable elections whose integrity can be verified by observers, candidates, media, and even voters themselves. ElectionGuard has been integrated into a variety of systems and used in actual public U.S. elections in Wisconsin, California, Idaho, Utah, and Maryland as well as in caucus elections in the U.S. Congress. It has also been used for civic voting in the...
Vote-by-mail is increasingly used in Europe and worldwide for government elections. Nevertheless, very few attempts have been made towards the design of verifiable vote-by-mail, and none of them come with a rigorous security analysis. Furthermore, the ballot privacy of the currently deployed (non-verifiable) vote-by-mail systems relies on procedural means that a single malicious operator can bypass. We propose a verifiable vote-by-mail system that can accommodate the constraints of many...
For more than forty years, two principal questions have been asked when designing verifiable election systems: how will the integrity of the results be demonstrated and how will the privacy of votes be preserved? Many approaches have been taken towards answering the first question such as use of MixNets and homomorphic tallying. But in the academic literature, the second question has always been answered in the same way: decryption capabilities are divided amongst multiple independent...
Universal verifiability is a must-to-have for electronic voting schemes. It is essential to ensure honest behavior of all the players during the whole process, together with the eligibility. However, it should not endanger the privacy of the individual votes, which is another major requirement. Whereas the first property prevents attacks during the voting process, privacy of the votes should hold forever, which has been called everlasting privacy. A classical approach for universal...
Fully homomorphic encryption (FHE) allows for evaluating arbitrary functions over encrypted data. In Multi-party FHE applications, different parties encrypt their secret data and submit ciphertexts to a server, which, according to the application logic, performs homomorphic operations on them. For example, in a secret voting application, the tally is computed by summing up the ciphertexts encoding the votes. Valid encrypted votes are of the form $E(0)$ and $E(1)$. A malicious voter could...
Linkable ring signatures are an important cryptographic primitive for anonymized applications, such as e-voting, e-cash and confidential transactions. To eliminate backdoor and overhead in a trusted setup, transparent setup in the discrete logarithm or pairing settings has received considerable attention in practice. Recent advances have improved the proof sizes and verification efficiency of linkable ring signatures with a transparent setup to achieve logarithmic bounds. Omniring (CCS '19)...
In the linear garbling model introduced by Zahur, Rosulek, and Evans (Eurocrypt 2015), garbling an AND gate requires at least \(2\kappa\) bits of ciphertext, where $\kappa$ is the security parameter. Though subsequent works, including those by Rosulek and Roy (Crypto 2021) and Acharya et al. (ACNS 2023), have advanced beyond these linear constraints, a more comprehensive design framework is yet to be developed. Our work offers a novel, unified, and arguably simple perspective on garbled...
We introduce a new cryptographic primitive, called Sybil-Resilient Anonymous (SyRA) signatures, which enable users to generate, on demand, unlinkable pseudonyms tied to any given context, and issue signatures on behalf of these pseudonyms. Concretely, given a personhood relation, an issuer (who may be a distributed entity) enables users to prove their personhood and extract an associated long-term key, which can then be used to issue signatures for any given context and message....
Sharding is a critical technique that enhances the scalability of blockchain technology. However, existing protocols often assume adversarial nodes in a general term without considering the different types of attacks, which limits transaction throughput at runtime because attacks on liveness could be mitigated. There have been attempts to increase transaction throughput by separately handling the attacks; however, they have security vulnerabilities. This paper introduces Reticulum, a novel...
Randomized Partial Checking (RPC} was proposed by Jakobsson, Juels, and Rivest and attracted attention as an efficient method of verifying the correctness of the mixing process in numerous applied scenarios. In fact, RPC is a building block for many electronic voting schemes, including Prêt à Voter, Civitas, Scantegrity II as well as voting-systems used in real-world elections (e.g., in Australia). Mixing is also used in anonymous transfers of cryptocurrencies. It turned out, however,...
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...
ZK-SNARKs, a fundamental component of privacy-oriented payment systems, identity protocols, or anonymous voting systems, are advanced cryptographic protocols for verifiable computation: modern SNARKs allow to encode the invariants of a program, expressed as an arithmetic circuit, in an appropriate constraint language from which short, zero-knowledge proofs for correct computations can be constructed. One of the most important computations that is run through SNARK systems is the...
Recently, Qiu et al. proposed a semi-quantum voting scheme based on the ring signature (International Journal of Theoretical Physics, 60: 1550–1555(2021)), in which the signer and verifier only need measure the received particles with Z-basis and perform some classical simple encryption/decryption operations on the classical message. Although their scheme is very efficient, it cannot resist against the eavesdropping attacks and forgery attack. In this paper, first, the eavesdropping attacks...
We present a general method to simplify soundness proofs under certain conditions. Given an adversary $\mathcal{A}$ able to break a scheme $S$ with non-negligible probability $t$, we define the concept of $\textit{trace}$ of a $\textit{winning configuration}$, which is already implicitly used in soundness proofs. If a scheme can be constructed that (1) takes a random configuration $e$, being the inputs and execution environment of $\mathcal{A}$, (2) "guesses" a trace, (3) modifies $e$ based...
Instant Runoff Voting (IRV) is one example of ranked-choice voting. It provides many known benefits when used in elections, such as minimising vote splitting, ensuring few votes are wasted, and providing resistance to strategic voting. However, the voting and tallying procedures for IRV are much more complicated than those of plurality and are both error-prone and tedious. Many automated systems have been proposed to simplify these procedures in IRV. Some of these also employ cryptographic...
We consider how to design an anonymous data collection protocol that enforces compliance rules. Imagine that each client contributes multiple data items (e.g., votes, location crumbs, or secret shares of its input) to an anonymous network, which mixes all clients' data items so that the receiver cannot determine which data items belong to the same user. Now, each user must prove to an auditor that the set it contributed satisfies a compliance predicate, without identifying which items it...
Electronic voting has occupied a large part of the cryptographic protocols literature. The recent reality of blockchains---in particular their need for online governance mechanisms---has put new parameters and requirements to the problem. We identify the key requirements of a blockchain governance mechanism, namely correctness (including eliminative double votes), voter anonymity, and traceability, and investigate mechanisms that can achieve them with minimal interaction and under...
Counter-strategies are key components of coercion-resistant voting schemes, allowing voters to submit votes that represent their own intentions in an environment controlled by a coercer. By deploying a counter-strategy a voter can prevent the coercer from learning if the voter followed the coercer’s instructions or not. Two effective counter-strategies have been proposed in the literature, one based on fake credentials and another on revoting. While fake-credential schemes assume that voters...
Bulletin boards (BB) are important cryptographic building blocks that, at their core, provide a broadcast channel with memory. BBs are widely used within many security protocols, including secure multi-party computation protocols, e-voting systems, and electronic auctions. Even though the security of protocols crucially depends on the underlying BB, as also highlighted by recent works, the literature on constructing secure BBs is sparse. The so-far only provably secure BBs require trusted...
Blind Signatures are a useful primitive for privacy preserving applications such as electronic payments, e-voting, anonymous credentials, and more. However, existing practical blind signature schemes based on standard assumptions require either pairings or lattices. We present the first practical construction of a round-optimal blind signature in the random oracle model based on standard assumptions without resorting to pairings or lattices. In particular, our construction is secure under...
India is the largest democracy by population and has one of the largest deployments of e-voting in the world for national elections. However, the e-voting machines used in India are not end-to-end (E2E) verifiable. The inability to verify the tallying integrity of an election by the public leaves the outcome open to disputes. E2E verifiable e-voting systems are commonly regarded as the most promising solution to address this problem, but they had not been implemented or trialed in India. It...
Regular access to unpredictable and bias-resistant randomness is important for applications such as blockchains, voting, and secure distributed computing. Distributed random beacon protocols address this need by distributing trust across multiple nodes, with the majority of them assumed to be honest. Numerous applications across the blockchain space have led to the proposal of several distributed random beacon protocols, with some already implemented. However, many current random beacon...
A $t$-out-of-$n$ threshold decryption system assigns key shares to $n$ parties so that any $t$ of them can decrypt a well-formed ciphertext. Existing threshold decryption systems are not secure when these parties are rational actors: an adversary can offer to pay the parties for their key shares. The problem is that a quorum of $t$ parties, working together, can sell the adversary a decryption key that reveals nothing about the identity of the traitor parties. This provides a risk-free...
We present a deterministic synchronous protocol for binary Byzantine Agreement against a corrupt minority with adaptive $O(n\cdot f)$ communication complexity, where $f$ is the exact number of corruptions. Our protocol improves the previous best-known deterministic Byzantine Agreement protocol developed by Momose and Ren (DISC 2021), whose communication complexity is quadratic, independent of the exact number of corruptions. Our approach combines two distinct primitives that we introduce...
Digital signatures are a cornerstone of security and trust in cryptography, providing authenticity, integrity, and non-repudiation. Despite their benefits, traditional digital signature schemes suffer from inherent immutability, offering no provision for a signer to retract a previously issued signature. This paper introduces the concept of a withdrawable signature scheme, which allows for the retraction of a signature without revealing the signer's private key or compromising the security...
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...
Typically, a decentralized collaborative blockchain decision-making mechanism is realized by remote voting. To date, a number of blockchain voting schemes have been proposed; however, to the best of our knowledge, none of these schemes achieve coercion-resistance. In particular, for most blockchain voting schemes, the randomness used by the voting client can be viewed as a witness/proof of the actual vote, which enables improper behaviors such as coercion and vote-buying. Unfortunately, the...
In [1], Sarier presents a practical biometric-based non-transferable credential scheme that maintains the efficiency of the underlying Brands credential. In this paper, we design a new Blockchain-Based E-Voting (BBEV) scheme that combines the system of [1] with encrypted Attribute Based Credentials for a non-transferable code-voting approach to achieve efficient, usable, anonymous, transparent, auditable, verifiable, receipt-free and coercion-resistant remote voting system for small/medium...
Electronic voting is one of the most interesting application of modern cryptography, as it involves many innovative tools (such as homomorphic public-key encryption, non-interactive zero-knowledge proofs, and distributed cryptography) to guarantee several a priori contradictory security properties: the integrity of the tally and the privacy of the individual votes. While many efficient solutions exist for honest-but-curious voters, that follow the official procedure but try to learn more...
Auction and voting schemes play a crucial role in the Web3 ecosystem. Yet currently deployed implementations either lack privacy or require at least two rounds, hindering usability and security. We introduce Cicada, a general framework for using linearly homomorphic time-lock puzzles (HTLPs) to enable provably secure, non-interactive private auction and voting protocols. We instantiate our framework with an efficient new HTLP construction and novel packing techniques that enable succinct...
In this paper we address the problem of recovery from failures without re-running entire elections when elections fail to verify. We consider the setting of $\textit{dual voting}$ protocols, where the cryptographic guarantees of end-to-end verifiable voting (E2E-V) are combined with the simplicity of audit using voter-verified paper records (VVPR). We first consider the design requirements of such a system and then suggest a protocol called $\textit{OpenVoting}$, which identifies a...
Modern e-voting systems provide what is called verifiability, i.e., voters are able to check that their votes have actually been counted despite potentially malicious servers and voting authorities. Some of these systems, called tally-hiding systems, provide increased privacy by revealing only the actual election result, e.g., the winner of the election, but no further information that is supposed to be kept secret. However, due to these very strong privacy guarantees, supporting complex...
Classic BFT consensus protocols guarantee safety and liveness for all clients if fewer than one-third of replicas are faulty. However, in applications such as high-value payments, some clients may want to prioritize safety over liveness. Flexible consensus allows each client to opt for a higher safety resilience, albeit at the expense of reduced liveness resilience. We present the first construction that allows optimal safety-liveness tradeoff for every client simultaneously. This...
A linkable ring signature allows a user to sign anonymously on behalf of a group while ensuring that multiple signatures from the same user are detected. Applications such as privacy-preserving e-voting and e-cash can leverage linkable ring signatures to significantly improve privacy and anonymity guarantees. To scale to systems involving large numbers of users, short signatures with fast verification are a must. Concretely efficient ring signatures currently rely on a trusted authority...
Jitsi Meet is an open-source video conferencing system, and a popular alternative to proprietary services such as Zoom and Google Meet. The Jitsi project makes strong privacy and security claims in its advertising, but there is no published research into the merits of these claims. Moreover, Jitsi announced end-to-end encryption (E2EE) support in April 2020, and prominently features this in its marketing. We present an in-depth analysis of the design of Jitsi and its use of cryptography....
Decentralized apps (DApps) often hold significant cryptocurrency assets. In order to manage these assets and coordinate joint investments, shareholders leverage the underlying smart contract functionality to realize a transparent, verifiable, and secure decision-making process. That is, DApps implement proposal-based voting. Permissionless blockchains, however, lead to a conflict between transparency and anonymity; potentially preventing free decision-making if individual votes and...
An interesting approach to achieving verifiability in voting systems is to make use of tracking numbers. This gives voters a simple way of verifying that their ballot was counted: they can simply look up their ballot/tracker pair on a public bulletin board. It is crucial to understand how trackers affect other security properties, in particular privacy. However, existing privacy definitions are not designed to accommodate tracker-based voting systems. Furthermore, the addition of trackers...
In the threshold version of Paillier's encryption scheme, a set of parties collectively holds the secret decryption key through a secret sharing scheme. Whenever a ciphertext is to be decrypted, the parties send their decryption shares, which are then verified for correctness and combined into the plaintext. The scheme has been widely adopted in various applications, from secure voting to general purpose MPC protocols. However, among the handful existing proposals for a maliciously...
In recent years, there has been much focus on developing core cryptographic primitives based on lattice assumptions, driven by the NIST cal for post-quantum key encapsulation and digital signature algorithms. However, more work must be conducted on efficient privacy-preserving protocols with post-quantum security. Electronic voting is one such privacy-preserving protocol whose adoption is increasing across the democratic world. E-voting offers both a fast and convenient alternative to...
Coercion-resistance is one of the most challenging security properties to achieve when designing an e-voting protocol. The JCJ voting scheme, proposed in 2005 by Juels, Catalano and Jakobsson, is one of the first voting systems where coercion-resistance was rigorously defined and achieved, making JCJ the benchmark for coercion-resistant protocols. Recently, the coercion-resistance definition proposed in JCJ has been disputed and improved by Cortier, Gaudry, and Yang. They identified a major...
A natural approach to anonymous voting over Ethereum assumes that there is an off-chain aggregator that performs the following task. The aggregator receives valid signatures of YES/NO preferences from eligible voters and uses them to compute a zk-SNARK proof of the fact that the majority of voters have cast a preference for YES or NO. Then, the aggregator sends to the smart contract the zk-SNARK proof, the smart contract verifies the proof and can trigger an action (e.g., a transfer of...
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...
Majority voting is a simple mathematical function that returns the value that appears most often in a set. As a popular decision fusion technique, the majority voting function (MVF) finds applications in resolving conflicts, where a number of independent voters report their opinions on a classification problem. Despite its importance and its various applications in ensemble learning, data crowd-sourcing, remote sensing, and data oracles for blockchains, the accuracy of the MVF for the...
Blind signatures were originally introduced by Chaum (CRYPTO ’82) in the context of privacy-preserving electronic payment systems. Nowadays, the cryptographic primitive has also found applications in anonymous credentials and voting systems. However, many practical blind signature schemes have only been analysed in the game-based setting where a single signer is present. This is somewhat unsatisfactory as blind signatures are intended to be deployed in a setting with many signers. We address...
Secure shuffle is an important primitive that finds use in several applications such as secure electronic voting, oblivious RAMs, secure sorting, to name a few. For time-sensitive shuffle-based applications that demand a fast response time, it is essential to design a fast and efficient shuffle protocol. In this work, we design secure and fast shuffle protocols relying on the techniques of secure multiparty computation. We make several design choices that aid in achieving highly efficient...
We study the rational behaviors of agents in DAG-Based Distributed Ledgers. We an- alyze generic algorithms that encapsulate the main actions of agents in a DAG-based dis- tributed ledger: voting for a block, and checking its validity. Knowing that those actions have costs, and validating a block gives rewards to agents who participated in the validation procedure, we study using game theory how strategic agents behave while trying to maximize their gains. We consider scenarios with...
Long-term security, a variant of Universally Composable (UC) security introduced by Müller-Quade and Unruh (JoC ’10), allows to analyze the security of protocols in a setting where all hardness assumptions no longer hold after the protocol execution has finished. Such a strict notion is highly desirable when properties such as input privacy need to be guaranteed for a long time, e.g. zero-knowledge proofs for secure electronic voting. Strong impossibility results rule out so-called...
This paper presents a novel e-voting scheme that combines Group Identity-based Identification (GIBI) with Homomorphic Encryption (HE) based on the discrete logarithmic assumption. The proposed scheme uses the Schnorr-like GIBI scheme for voter identification and authorization using Zero-Knowledge (ZK) proof to ensure the anonymity and eligibility of voters. The use of Distributed ElGamal (DE) provides fairness and receipt-freeness, while the use of partial shares for decryption enables...
State machine replication (SMR) allows nodes to jointly maintain a consistent ledger, even when a part of nodes are Byzantine. To defend against and/or limit the impact of attacks launched by Byzantine nodes, there have been proposals that combine reputation mechanisms to SMR, where each node has a reputation value based on its historical behaviours, and the node’s voting power will be proportional to its reputation. Despite the promising features of reputation-based SMR,...
Discrete logarithm problem(DLP) is the pillar of many cryptographical schemes. We propose an improvement to the Gaudry-Schost algorithm, for multi-dimensional DLP. We have derived the cost estimates in general and specialized cases, which prove efficiency of our new method. We report the implementation of our algorithm, which confirms the theory. Both theory and experiments val- idate the fact that the advantage of our algorithm increases for large sizes, which helps in...
In the current context of the increasing need for data privacy and quantum computing no longer being just a novel concept, Fully Homomorphic Encryption presents us with numerous quantum-secure schemes which have the concept of enabling data processing over encrypted data while not decrypting it behind. While not entirely usable at the present time, recent research has underlined its practical uses applied to databases, cloud computing, machine learning, e-voting, and IoT computing. In this...
Voting mechanisms allow the expression of the elections by a democratic approach. Any voting scheme must ensure, preferably in an efficient way, a series of safety measures such as confidentiality, integrity and anonymity. Since the 1980s, the concept of electronic voting became more and more of interest, being an advantageous or even necessary alternative for the organization of secure elections. In this paper, we give an overview for the e-voting mechanisms together with the security...
Most cryptographic protocols model a player’s knowledge of secrets in a simple way. Informally, the player knows a secret in the sense that she can directly furnish it as a (private) input to a protocol, e.g., to digitally sign a message. The growing availability of Trusted Execution Environments (TEEs) and secure multiparty computation, however, undermines this model of knowledge. Such tools can encumber a secret sk and permit a chosen player to access sk conditionally, without actually...
Blind signature schemes are the essential element of many complex information systems such as e-cash and e-voting systems. They should provide two security properties: unforgeability and blindness. The former one is standard for all signature schemes and ensures that a valid signature can be generated only during the interaction with the secret signing key holder. The latter one is more specific for this class of signature schemes and means that there is no way to link a (message, signature)...
E-voting offers significant potential savings in time and money compared to current voting systems. Unfortunately, many current e-voting schemes are susceptible to quantum attacks. In this paper, we expand upon EVOLVE, an existing lattice-based quantum-secure election scheme introduced by Pino et al. We are able to make these expansions by extending the dimensions of the voter's ballot and creating additional proofs, allowing for applicability to realistic election schemes. Thus, we present...
We conduct a security analysis of the e-voting protocol used for the largest political election using e-voting in the world, the 2022 French legislative election for the citizens overseas. Due to a lack of system and threat model specifications, we built and contributed such specifications by studying the French legal framework and by reverse-engineering the code base accessible to the voters. Our analysis reveals that this protocol is affected by two design-level and implementation-level...
This document details the cryptographic analysis of the sVote v2.2.1 system - an e-voting solution developed by Scytl for the Switzerland context. We prove the complete verifiability and privacy under the Swiss legislation's informally stated goals. First, we derive the trust model for complete verifiability and voting secrecy from the Swiss Chancellery's requirements [1][2], supporting our interpretation by quotes from and references to relevant excerpts of the ordinance and the...
The proliferation of Decentralised Finance (DeFi) and Decentralised Autonomous Organisations (DAO), which in current form are exposed to front-running of token transactions and proposal voting, demonstrate the need to shield user inputs and internal state from the parties executing smart contracts. In this work we present “Eagle”, an efficient UC-secure protocol which efficiently realises a notion of privacy preserving smart contracts where both the amounts of tokens and the auxiliary data...
Partially blind signatures, an extension of ordinary blind signatures, are a primitive with wide applications in e-cash and electronic voting. One of the most efficient schemes to date is the one by Abe and Okamoto (CRYPTO 2000), whose underlying idea - the OR-proof technique - has served as the basis for several works. We point out several subtle flaws in the original proof of security, and provide a new detailed and rigorous proof, achieving similar bounds as the original work. We...
We solve a long-standing challenge to the integrity of votes cast without the supervision of a voting booth: “improper influence,” which we define as any combination of vote buying and voter coercion. Our approach allows each voter, or their trusted agent(s), to cancel their vote in a way that is unstoppable, irrevocable, and forever unattributable to the voter. In particular, our approach enhances security of online, remote, public-sector elections, for which there is a growing need and the...
Privacy is a notoriously difficult property to achieve in complicated systems and especially in electronic voting schemes. Moreover, electronic voting schemes is a class of systems that require very high assurance. The literature contains a number of ballot privacy definitions along with security proofs for common systems. Some machine-checked security proofs have also appeared. We define a new ballot privacy notion that captures a larger class of voting schemes. This notion improves on the...
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...
Unique ring signatures (URS) were introduced by Franklin and Zhang (FC 2012) as a unification of linkable and traceable ring signatures. In URS, each member within a ring can only produce, on behalf of the ring, at most one signature for a message. Applications of URS potentially are e-voting systems and e–token systems. In blockchain technology, URS has been implemented for mixing contracts. However, existing URS schemes are based on the Discrete Logarithm Problem, which is insecure in the...
The verifiable encryption of bits is the main computational step that is needed to prepare ballots in many practical voting protocols. Its computational load can also be a practical bottleneck, preventing the deployment of some protocols or requiring the use of computing clusters. We investigate the question of producing many verifiably encrypted bits in an efficient and portable way, using as a baseline the protocol that is in use in essentially all modern voting systems and libraries...
The security of code-based cryptography relies primarily on the hardness of generic decoding with linear codes. The best generic decoding algorithms are all improvements of an old algorithm due to Prange: they are known under the name of information set decoders (ISD). A while ago, a generic decoding algorithm which does not belong to this family was proposed: statistical decoding. It is a randomized algorithm that requires the computation of a large set of parity-checks of moderate...
We introduce a new way to conduct election audits using untrusted scanners. Post-election audits perform statistical hypothesis testing to confirm election outcomes. However, existing approaches are costly and laborious for close elections---often the most important cases to audit---requiring extensive hand inspection of ballots. We instead propose automated consistency checks, augmented by manual checks of only a small number of ballots. Our protocols scan each ballot twice, shuffling the...
The re-encryption mix-net (RMN) is a basic cryptographic tool that is widely used in the privacy protection domain and requires anonymity support; for example, it is used in electronic voting, web browsing, and location systems. To protect information about the relationship between senders and messages, a number of mix servers in RMNs shuffle and forward a list of input ciphertexts in a cascading manner. The output of the last mix server is decrypted to yield the set of original messages....
CCA-like game-based security definitions capture confidentiality by asking an adversary to distinguish between honestly computed encryptions of chosen plaintexts. In the context of voting systems, such guarantees have been shown to be sufficient to prove ballot privacy (Asiacrypt'12). In this paper, we observe that they fall short when one seeks to obtain receipt-freeness, that is, when corrupted voters who submit chosen ciphertexts encrypting their vote must be prevented from proving...
There are numerous settings in which people's preferences are aggregated outside of formal elections, and where privacy and verification are important but the stringent authentication and coercion-resistant properties of government elections do not apply, a prime example being social media platforms. These systems are often iterative and have no trusted authority, in contrast to the centrally organised, single-shot elections on which most of the literature is focused. Moreover, they require...
Replay attacks are among the most well-known attacks against vote privacy. Many e-voting systems have been proven vulnerable to replay attacks, including systems like Helios that are used in real practical elections. Despite their popularity, it is commonly believed that replay attacks are inefficient but the actual threat that they pose to vote privacy has never been studied formally. Therefore, in this paper, we precisely analyze for the first time how efficient replay attacks really...
Side-channel resilience is a crucial feature when assessing whether a post-quantum cryptographic proposal is sufficiently mature to be deployed. In this paper, we propose a generic and efficient adaptive approach to improve the sample complexity (i.e., the required number of traces) of plaintext-checking (PC) oracle-based side-channel attacks (SCAs), a major class of key recovery chosen-ciphertext SCAs on lattice-based key encapsulation mechanisms. This new approach is preferable when the...
Electronic voting has long been an area of active and challenging research. Security properties relevant to physical voting in elections with a variety of threat models and priorities are often difficult to reproduce in cryptographic systems and protocols. Existing work in this space often focuses on the privacy of ballot contents, assurances to voters that their votes are tabulated, and verification that election results are correct; however, privacy of voter identity is often offloaded to...
In recent years, lattice-based secure multi-party computation (MPC) has seen a rise in popularity and is used more and more in large scale applications like privacy-preserving cloud computing, electronic voting, or auctions. Many of these applications come with the following high security requirements: a computation result should be publicly verifiable, with everyone being able to identify a malicious party and hold it accountable, and a malicious party should not be able to corrupt the...
Coercion-resistance is a security property of electronic voting, often considered as a must-have for high-stake elections. The JCJ voting scheme, proposed in 2005 by Juels, Catalano and Jakobsson, is still the reference paradigm when designing a coercion-resistant protocol. We highlight a weakness in JCJ that is also present in all the systems following its general structure. This comes from the procedure that precedes the tally, where the trustees remove the ballots that should not be...
Cryptographic voting protocols have recently seen much interest from practitioners due to their (planned) use in countries such as Estonia, Switzerland, France, and Australia. Practical protocols usually rely on tested designs such as the mixing-and-decryption paradigm. There, multiple servers verifiably shuffle encrypted ballots, which are then decrypted in a distributed manner. While several efficient protocols implementing this paradigm exist from discrete log-type assumptions, the...
As a common consensus mechanism used in blockchain systems, DPoS uses voting to select committee members who will generate the corresponding blocks. In order to elect committee members as fairly as possible, the vague sets are introduced into the voting phase of DPoS. In the vague sets based model proposed by Xu et al., the voting nodes can vote for, oppose or abstain from it. In this paper, we improve this vague set based model by introducing a new mapping from the vague set to fuzzy set...
We present a novel cryptographic primitive, blind accumulator, aimed at constructing e-voting systems. Blind accumulators collect private keys of eligible voters in a decentralized manner not getting information about the keys. Once the accumulation is complete, a voter processes the resulting accumulator deriving a public key that refers to the private key previously added by this voter. Public keys are derived deterministically and can therefore stand as fixed voter pseudonyms. The voter...
The Open Vote Network is a self-tallying decentralized e-voting protocol suitable for boardroom elections. Currently, it has two Ethereum-based implementations: the first, by McCorry et al., has a scalability issue since all the computations are performed on-chain. The second implementation, by Seifelnasr et al., solves this issue partially by assigning a part of the heavy computations to an off-chain untrusted administrator in a verifiable manner. As a side effect, this second...
We explore definitions of verifiability by Juels et al. (2010), Cortier et al. (2014), and Kiayias et al. (2015). We discover that voting systems vulnerable to attacks can be proven to satisfy each of those definitions and conclude they are unsuitable for the analysis of voting systems. Our results will fuel the exploration for a new definition.
An aggregate signature (AS) scheme allows an unspecified aggregator to compress many signatures into a short aggregation. AS schemes can save storage costs and accelerate verification. They are desirable for applications where many signatures need to be stored, transferred, or verified together, like blockchain systems, network routing, e-voting, and certificate chains. However, constructing AS schemes based on general groups, only requiring the hardness of the discrete logarithm problem, is...
Public random beacons publish random numbers at regular intervals, which anyone can obtain and verify. The design of public distributed random beacons has been an exciting research direction with significant implications for blockchains, voting, and beyond. Distributed random beacons, in addition to being bias-resistant and unpredictable, also need to have low communication overhead and latency, high resilience to faults, and ease of reconfigurability. Existing synchronous random beacon...
Ever since the appearance of quantum computers, prime factoring and discrete logarithm based cryptography has been put in question, giving birth to the so called post-quantum cryptography. The most prominent field in post-quantum cryptography is lattice-based cryptography, protocols that are proved to be as difficult to break as certain difficult lattice problems like Learning With Errors (LWE) or Ring Learning With Errors (RLWE). Furthermore, the application of cryptographic techniques to...
We propose new zero-knowledge proofs for efficient and post-quantum ring confidential transaction (RingCT) protocols based on lattice assumptions in Blockchain systems. First, we introduce an inner-product based linear equation satisfiability approach for balance proofs with a wide range (e.g. 64-bit precision). Unlike existing balance proofs that require additional proofs for some ''corrector values'' [CCS'19], our approach avoids the corrector values for better efficiency. Furthermore, we...
This paper studies quantitative relationships between privacy, verifiability, accountability, and coercion-resistance of voting protocols. We adapt existing definitions to make them better comparable with each other and determine which bounds a certain requirement on one property poses on some other property. It turns out that, in terms of proposed definitions, verifiability and accountability do not necessarily put constraints on privacy and coercion-resistance. However, the relations...
Mix-networks were first proposed by Chaum in the late 1970s -- early 1980s as a general tool for building anonymous communication systems. Classical mix-net implementations rely on standard public key primitives (e.g. ElGamal encryption) that will become vulnerable when a sufficiently powerful quantum computer will be built. Thus, there is a need to develop quantum-resistant mix-nets. This paper focuses on the application case of electronic voting where the number of votes to be mixed may...
This paper presents the details of one of the two cryptographic remote e-voting protocols used in the Russian parliamentary elections of 2021. As the official full version of the scheme has never been published by the election organisers, our paper aims at putting together as complete picture as possible from various incomplete sources. As all the currently available sources are in Russian, our presentation also aims at serving the international community by making the description available...
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...
Proof of liabilities (PoL) allows a prover to prove his/her liabilities to a group of verifiers. This is a cryptographic primitive once used only for proving financial solvency but is also applicable to domains outside finance, including transparent and private donations, new algorithms for disapproval voting and publicly verifiable official reports such as COVID-19 daily cases. These applications share a common nature in incentives: it's not in the prover's interest to increase his/her...
A peer-to-peer, permissionless, and distributed cryptographic voting system that relies only on the existence of generic digital signatures and encryption.
Ring signatures enable a signer to sign a message on behalf of a group anonymously, without revealing her identity. Similarly, threshold ring signatures allow several signers to sign the same message on behalf of a group; while the combined signature reveals that some threshold $t$ of the group members signed the message, it does not leak anything else about the signers' identities. Anonymity is a central feature in threshold ring signature applications, such as whistleblowing, e-voting...