A Scalable Blockchain Framework for Verifiable and Private Ranked-Choice Online Voting

Electronic voting systems are designed to modernise democratic processes by providing efficient, transparent, and accessible elections. They promise rapid tallying, reduced human error, and increased participation. However, large-scale deployment remains hindered by unresolved concerns around security, privacy, scalability, and trust. Direct recording electronic machines suffer from limited verifiability. In Internet voting, the more fundamental risks stem from compromised end-user devices, difficulty in achieving end-to-end verifiability that ordinary voters can meaningfully check, and exposure to coercion and vote buying, rather than generic cyberattacks alone. Blockchain-based approaches, while offering immutability and public auditability, face significant scalability limits. Network throughput and latency constrain election-sized workloads, fee volatility creates cost uncertainty, and per-vote on-chain actions, such as posting ballots and verifying cryptographic proofs, incur prohibitive costs that grow linearly with the number of voters. The openness of public ledgers also leaks metadata that can erode privacy. Consequently, achieving accountability and transparency without sacrificing individual ballot secrecy and practical efficiency remains a central challenge. This thesis addresses these challenges by providing the first thorough analysis of a ranked-choice blockchain election protocol that had not been previously examined in detail. The analysis identifies critical limitations related to privacy and efficiency that weaken unlinkability and verifiability. Building on these findings, the first significant contribution of this thesis is the design of a new, verifiable, and privacy-preserving voting framework that eliminates the need for a trusted tallying authority. The scheme employs anonymous participation tokens and nullifiers to enforce one-time eligibility. At the same time, voters cast encrypted ballots accompanied by zero-knowledge proofs that confirm eligibility, correctness, and uniqueness without disclosing their identity or the content of their vote. Tallying is achieved through a decentralised threshold decryption process that ensures fairness and confidentiality. The second significant contribution of this thesis is an efficient proof-batching and verification mechanism that addresses the scalability bottlenecks of existing blockchain-based approaches. By aggregating multiple proofs off-chain and submitting a single, succinct batch proof with updated commitments, the protocol reduces on-chain verification to a near-constant cost per voter. This significantly decreases computational and financial overhead, enabling scalability to large elections. The proposed framework is analysed under realistic adversarial models and shown to achieve privacy, eligibility, uniqueness, and universal verifiability. Performance evaluation demonstrates that the batching mechanism substantially lowers costs compared to existing protocols. Overall, this research advances the state of the art in blockchain-based electronic voting by providing the first comprehensive evaluation of a ranked-choice protocol and proposing novel mechanisms that overcome its limitations, thereby laying a foundation for secure, transparent, and scalable digital elections.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

De Montfort University

Year dc:date.issued

2026

Author dc:creator

• Alown, Mosbah Ersan

Licence

• https://dora.dmu.ac.uk/bitstreams/fad4207c-d9fc-439b-998c-3c070c18989d/download