Smart Contracts Overview

This section provides a high-level overview of the smart contracts developed for the Blockchain Voting System. The contracts are written in Solidity and deployed on a compatible blockchain network.

For detailed technical specifications of each contract, please refer to the Technical Details page.

Core Contracts

The smart contract suite employs a modular design approach, where core entities of the voting system are encapsulated within their own dedicated Solidity contracts. This structure enhances clarity, maintainability, and reusability by separating concerns.

Voter.sol

Defines the Voter struct, a fundamental data structure for managing voter status (registered, voted) within the election system. It is a blueprint for voter objects, not a deployable contract.

Candidate.sol

Defines the Candidate struct, representing a candidate participating in an election. It includes fields for a unique ID, name, position, and an IPFS Content Identifier (CID) for additional profile information. This is a data structure definition, not a deployable contract.

Party.sol

Manages political parties, their details (name, slogan, IPFS CID for logo), and the candidates associated with them. Each Party contract is deployed independently and allows its administrator to register and manage candidates.

Election.sol

Manages the lifecycle of a single election, including its start and end times, participating parties, voter registration, and vote casting. It interacts with Party contracts and utilizes the Voter struct to track voter status and votes.

VotingSystem.sol

Serves as the central hub for creating and managing elections and political parties. It acts as a factory for Election and Party contracts, allowing an administrator to create new elections and parties and retrieve their addresses.

ZK Privacy Integration

The system integrates Zero-Knowledge (ZK) proofs using Semaphore to ensure voter privacy:

Semaphore Integration

• Anonymous Voting: Voters can prove eligibility without revealing identity
• Group Membership: Voters belong to Semaphore groups for each election
• Nullifier System: Prevents double voting while maintaining anonymity
• ZK Proof Generation: Client-side proof generation for voter eligibility

Privacy Guarantees

• Voter Anonymity: Votes cannot be linked to specific voter identities
• Unlinkability: Multiple actions by same voter appear unrelated
• Deniability: Voters cannot prove how they voted

Gasless Transaction Architecture

To hide blockchain complexity from voters, the system implements a relay architecture:

Backend Relayer

• Gas Abstraction: Backend pays gas fees for voter transactions
• Wallet Management: Backend wallet handles all blockchain interactions
• User Experience: Voters interact with traditional web app interface
• Transaction Relay: Backend submits signed transactions on behalf of voters

Authentication Flow

• Traditional Login: Email/password or social login for voters
• ZK Proof Generation: Client-side generation of eligibility proofs
• Backend Submission: Relay service submits votes to blockchain
• Confirmation: Immediate feedback to voters

ZK Privacy Integration

The system integrates Zero-Knowledge proofs for voter privacy using Semaphore:

Semaphore Integration

• Voters generate ZK proofs to prove eligibility without revealing identity
• Semaphore groups manage voter anonymity
• Nullifier system prevents double voting

Privacy Guarantees

• Votes cannot be linked to specific voters
• Voter eligibility is proven without revealing identity
• Unlinkability between votes from the same voter

Gasless Transaction Architecture

To hide blockchain complexity from voters:

Backend Relay

• Backend submits transactions to blockchain on behalf of voters
• Voters don't need wallets or pay gas fees
• Traditional authentication (email/password) used instead

User Experience

• Seamless web application experience
• No wallet installation required
• Instant vote confirmation