A Peered Bulletin Board for Robust Use in Verifiable Voting Systems

Abstract

The Web Bulletin Board (WBB) is a key component of verifiable election systems. It is used in the context of election verification to publish evidence of voting and tallying that voters and officials can check, and where challenges can be launched in the event of malfeasance. In practice, the election authority has responsibility for implementing the web bulletin board correctly and reliably, and will wish to ensure that it behaves correctly even in the presence of failures and attacks. To ensure robustness, an implementation will typically use a number of peers to be able to provide a correct service even when some peers go down or behave dishonestly. In this paper we propose a new protocol to implement such a Web Bulletin Board, motivated by the needs of the vVote verifiable voting system. Using a distributed algorithm increases the complexity of the protocol and requires careful reasoning in order to establish correctness. Here we use the Event-B modelling and refinement approach to establish correctness of the peered design against an idealised specification of the bulletin board behaviour. In particular we show that for n peers, a threshold of t > 2n/3 peers behaving correctly is sufficient to ensure correct behaviour of the bulletin board distributed design. The algorithm also behaves correctly even if honest or dishonest peers temporarily drop out of the protocol and then return. The verification approach also establishes that the protocols used within the bulletin board do not interfere with each other. This is the first time a peered web bulletin board suite of protocols has been formally verified

Extending Helios Towards Private Eligibility Verifiability

“…The Bulletin Board Assumption can be facilitated either by establishing a central server, supervised by trusted third-party observers, or implemented in a distributed way (e.g. [14]). The Cryptography Assumption is common to the voting systems based on cryptographic mechanisms, and the Authentic List of Keys Assumption is based upon the public list of all eligible voters, the integrity of which is something that should be ensured in traditional elections as well.…”

Distributed, end-to-end verifiable, and privacy-preserving internet voting systems

“…Dini presents a distributed e-voting system, which however is not end-to-end verifiable [Dini 2003]. In [Culnane and Schneider 2014], there is a distributed BB implementation, also handling vote collection, according to the design of the vVote end-to-end verifiable e-voting system [Culnane et al 2015], which in turn is an adaptation of the Prêtà Voter e-voting system [Chaum et al 2005]. In [Culnane and Schneider 2014], the proper operation of the BB during ballot casting requires a trusted device for signature verification.…”

“…E-voting systems are a powerful technology to improve the election process. Kiosk-based evoting systems, e.g., [Chaum 2001;Chaum et al 2005;Fisher et al 2006;Chaum et al 2008;Benaloh et al 2013;Culnane and Schneider 2014], allow the tally to be produced faster, but require the voter's physical presence at the booth. Internet e-voting systems, e.g., [Cramer et al 1997;Adida 2008;Clarkson et al 2008;Kutylowski and Zagórski 2010;Gjøsteen 2013;Zagórski et al 2013;Chaum 2001;Chaum et al 2008;Zagórski et al 2013;Kiayias et al 2015], however, allow voters to cast their votes remotely.…”

A Framework for Analyzing Verifiability in Traditional and Electronic Exams

“…engages the typical exam roles: the candidate (C), the examiner (E), and the exam authority (EA) (called manager in the original paper). The protocol uses two particular building blocks: an exponential mixnet (NET) [19] and an append-only bulletin board (BB) [8]. The protocol's only trust assumption is that there is at least one honest server in NET.…”