IPFS Usage

This section details how IPFS is used within the Blockchain Voting System, including how data is uploaded, retrieved, and linked to smart contracts.

Overview

IPFS (InterPlanetary File System) is used in the Blockchain Voting System to provide decentralized storage for election-related media and metadata. This includes:

• Candidate profile pictures and bios
• Party logos and information
• Election descriptions and related documents
• Voter registration documents

By using IPFS, the system ensures that media files are:

• Permanently available (content-addressed storage)
• Tamper-proof (immutable once stored)
• Distributed (no single point of failure)
• Cost-effective (no recurring hosting costs)

Data Storage Architecture

Content Addressing

All files stored on IPFS are referenced by their Content Identifier (CID), which is a cryptographic hash of the file content. This ensures:

1. Immutability: Files cannot be changed without generating a new CID
2. Verifiability: Anyone can verify file integrity by hashing the content
3. Deduplication: Identical files are stored only once across the network

File Types and Usage

File Type	Usage	Example CID
Candidate Images	Profile pictures for candidates	QmCandidateImage123...
Party Logos	Visual representation of political parties	QmPartyLogo456...
Election Documents	Descriptions, rules, terms	QmElectionDoc789...
Voter Records	Registration and verification documents	QmVoterRecordABC...

Integration with Smart Contracts

Storing References

Rather than storing entire files on the blockchain (which would be expensive), smart contracts store only the CIDs:

struct Candidate {
    uint id;
    string name;
    string position;
    string cid; // IPFS CID for candidate image/bio
}

struct Party {
    uint id;
    string name;
    string slogan;
    string cid; // IPFS CID for party logo
}

Retrieving Files

When the frontend needs to display a candidate's photo:

1. Smart contract is queried for candidate data
2. CID is extracted from the candidate record
3. IPFS gateway is used to retrieve the file: https://ipfs.io/ipfs/{cid}
4. File is displayed to the user

Upload Process

1. File Preparation

Files are prepared for upload by:

• Validating file type and size limits
• Converting to web-friendly formats (JPEG, PNG, etc.)
• Generating thumbnails where appropriate

2. IPFS Upload

Files are uploaded to IPFS using:

• Local IPFS node (in development)
• Pinning service (in production)
• Content hashing to generate CID

3. Smart Contract Update

The generated CID is stored in the appropriate smart contract:

// Example: Updating a candidate with their IPFS CID
const candidateId = await votingSystem.registerCandidate(
  partyId,
  "John Doe",
  "President",
  "QmCandidateImage123..." // IPFS CID
);

Retrieval Process

1. Smart Contract Query

Frontend queries smart contract for entity data:

const candidate = await votingSystem.getCandidate(candidateId);
const candidateCid = candidate.cid; // IPFS CID

2. IPFS Gateway Access

Frontend retrieves file from IPFS via gateway:

const imageUrl = `https://ipfs.io/ipfs/${candidateCid}`;

3. File Display

Retrieved file is displayed in the UI.

Security Considerations

Content Integrity

• CIDs ensure files haven't been tampered with
• Frontend can verify file hashes if needed
• Pinning services provide redundancy

Privacy

• Files are public by default on IPFS
• Sensitive voter data should be encrypted before upload
• Access controls are implemented at the application layer

Best Practices

File Optimization

• Compress images before upload
• Use appropriate file formats (WebP for images)
• Implement proper sizing for different use cases

Pinning Strategy

• Use multiple pinning services for redundancy
• Implement automatic pinning for critical election data
• Consider unpinning expired election data to reduce costs

Error Handling

• Implement fallback gateways
• Cache frequently accessed files
• Handle IPFS gateway downtime gracefully

Example Implementation

Uploading a Candidate Image

// Frontend uploads image to IPFS
const file = document.getElementById('candidate-photo').files[0];
const cid = await ipfs.upload(file);

// Backend registers candidate with CID
const candidateId = await votingSystem.registerCandidate(
  partyId,
  name,
  position,
  cid
);

Displaying a Candidate Image

// Frontend retrieves candidate data
const candidate = await votingSystem.getCandidate(candidateId);

// Construct IPFS URL
const imageUrl = `https://ipfs.io/ipfs/${candidate.cid}`;

// Display image
document.getElementById('candidate-photo').src = imageUrl;

Future Enhancements

Encryption

• Encrypt sensitive files before IPFS upload
• Implement decryption keys for authorized access

Streaming

• Support for large video files
• Progressive loading for better UX

Caching

• Implement browser caching strategies
• Use CDNs for popular content