Design and implementation of cast-as-intended verifiability for a blockchain-based voting system

Abstract

Digitization of electoral processes depends on confident systems that produce verifiable evidence. The design and implementation of voting systems has been widely studied in prior research, bringing together expertise in many fields. Switzerland is organized in a federal, decentralized structure of independent governmental entities. Thus, its decentralized structure is a real-world example for implementing an electronic voting system, where trust is distributed among multiple authorities.This work outlines the design and implementation of a blockchainbased electronic voting system providing cast-as-intended verifiability. The generation of non-interactive zero-knowledge proofs of knowledge enables every voter to verify the encrypted vote, while maintaining the secrecy of the ballot. The Public Bulletin Board (PBB) is a crucial component of every electronic voting system, serving as a publicly verifiable log of communication and ballots -here a blockchain is used as the PBB. Also, the required cryptographic operations are in linear relation to the number of voters, making the outlined system fit for large-scale elections.

Æternum: A Decentralized Voting System with Unconditional Privacy

“…Although the prototype implementation uses Tendermint's consensus mechanism (requiring at least 2 /3 of all consensus nodes to behave honestly), a suitable alternative is Proof-of-Authority [29], [30]. For instance, in Switzerland, cantons, down to municipalities can participate in the consensus, only requiring at least 1 /2 nodes to behave honestly.…”

“…AEternum provides IV, since the voter can query the PBB to find out if the ballot was recorded correctly. However, this assumes that the voter's platform is trusted, i.e., not infected with malware corrupting the voter's view of the PBB, and thus, not providing any voting verification mechanism [29]. Malware on the voter's device can intercept all communications between the voter and the DPBB, thereby modifying the voter's ballot and reflecting an incorrect state of the DPBB in order to keep the voter from noticing the modifications.…”

“…In order to achieve UP, the deployment of a decentralized PBB is required. Distributed Ledgers (DL) offer a suitable approach to deploy a Decentralized PBB (DPBB) to achieve such a distribution of trust among authorities [29]. DLs are tamper-proof and immutable, replicate data securely, making them ideal for storing ballots that should not be manipulated by anyone [30].This paper proposes AEternum, the first DL-based REV system combining a voting scheme with UP and a public permissioned DL, which serves as a DPBB.…”

Fair Delegation of Digital Services Without Third Parties

“…By combining the advantages of the blockchain with smart contracts, the research community developed a profusion of distributed applications, e.g. a voting system for Switzerland [10]. Involving a trusted third party that punishes malicious actors requires setting up an escrow [11] to draw from if a misbehavior occurs, or a reputation system [12].…”

Proverum: A Hybrid Public Verifiability and Decentralized Identity Management

“…CaIV needs to be addressed, if the voter's platform cannot be controlled and trusted, which is typically the case, if the voter is able to cast an electronic ballot remotely. IV and CaIV together assure that the voter can detect that her vote was compromised, most probably by malicious code on the voting device [11]. While IV, UV, and E2E-V are of central importance for REV schemes, they are hard to prove in combination, but even harder to be deployed within an operational and practical RPV system.…”