Department Events

Title: End-to-end verifiable Voting Systems to Fully Verified Elections

By Peter Y A Ryan

Abstract:

The idea of end-to-end verifiable (E2E V) voting schemes has been around for over three decades. The goal is to ensure that any manipulation of any vote from the point of casting to the point of tallying is detectable by voters and/or observers, and ideally correctable. This should be achieved with minimal trust assumptions without trusting the correctness of the code running on voting machines, servers etc. At the same time, we need to guarantee conflicting properties like vote, privacy, coercion resistance etc.

E2E V is a laudable goal, essentially election dependability for the people by the people, and many excellent schemes have been proposed, and some prototyped and trialed, but to date none have seen widespread, long-term deployment. The begs the question: why has there been so little uptake of such schemes even though they are manifestly more trustworthy that the commercial systems that are in use? We suggest that a large part of the reluctance to deploy E2E V systems the need for voters to perform certain checks on encrypted ballots, the so-called “individual” checks. Such checks are a problem for usability, understandability and acceptability. Furthermore, if too few voters perform their checks, then the election cannot be deemed to have been verified, even if run on a verifiable system.

I will present an in-person scheme in which these checks are outsourced to independent auditors and for voters the experience is a simple and familiar vote and go. There is no longer any need or expectation for voters perform any checks (but the option can still be made available to them). In essence the idea is for the Election Authority to commit in advance to ballots that carry encryptions of the voting options. These can be audited before, during and after voting by independent observers and auditors. More exactly, what is committed to in the setup phase is ballots with malleable signatures over trivial encryptions of the voting options, allowing the options to be presented to the voters in plaintext. Ballot auditing now reduces to signature verification, which can be performed by anyone and is dispute-free. We also propose techniques to outsource the recorded-as-cast checks, that are also usually regarded as individual.

Thus, voters simply present their vote selection in plaintext to a scanner in the booth and then present the resulting printout showing a re-encryption of the vote along with transformed signature to the election officials. Assuming that independent auditors and observers perform sufficient audits, we have elections that are in fact verified rather than just verifiable. We refer to schemes with this property as “fully verified”. Time permitting, I will touch on the challenges of achieving this goal for online voting.

Short bio:

Peter Ryan is full Professor of Applied Security at the University of Luxembourg since Feb 2009, Emeritus from July 2025. He has over 30 years of experience in cryptography, information assurance and formal verification. He pioneered the application of process calculi to modelling and analysis of secure systems, in particular the characterization of non-interference and the analysis of security protocols. He has published extensively on cryptography, cryptographic protocols, security policies, mathematical models of computer security and, more recently, voter-verifiable election systems, Quantum Authenticated Key Establishment Protocols and post-quantum crypto.

He was awarded a PhD in mathematical physics from the University of London in 1982. He sits on or has sat on the program committees of numerous, prestigious security conferences, notably: IEEE Security and Privacy, IEEE Computer Security Foundations Workshop/Symposium (CSF), the European Symposium on Research in Computer Security (ESORICS). From 1999 to 2007 he was the President of the ESORICS Steering Committee. In 2016 he founded the Verifiable Voting series of workshops associated with Financial Crypto. He is a Visiting Professor at Surrey University and the ENS Paris.