🚀 Key Features

• Granular Chunking Dynamically divides files into at least 50 segments for fine-grained verification.

• Secure Hashing Encodes each chunk in Base64 and hashes with SHA-256 for consistent, tamper-proof digests.

• Merkle Tree Construction Recursively concatenates and hashes pairs of chunk hashes to compute a single Merkle root.

• REST API

  • POST /upload — Accepts file upload, returns Merkle JSON and root hash
  • POST /verify — Accepts original file + Merkle JSON, returns verification report

• Automatic Download Client-side download of generated Merkle JSON immediately after upload.

• Detailed Reports Displays root match status, corrupted-chunk count, and corruption percentage.

• CORS Enabled Seamless frontend-backend communication.

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🏗️ Architecture Overview

merkle-backend/
├── index.js               # Express server with file handling & Merkle logic
├── MerkleTree.js          # Merkle tree implementation
└── uploads/               # Stored files & Merkle JSON outputs

merkle-frontend/
├── src/
│   └── App.js             # React component for upload & verification UI
└── package.json           # Frontend dependencies & scripts

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⚙️ Prerequisites

• Node.js v14+
• npm (Node Package Manager)
• Git (optional)

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📦 Installation & Setup

Backend

cd path/to/merkle-backend
npm install
node index.js

Server runs on port 4000 by default.

Frontend

cd path/to/merkle-frontend
npm install
npm start

App runs on port 3000 by default.

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🎯 Usage

1. Upload & Generate

1. Click Upload & Generate.
2. File is chunked, hashed, and Merkle tree is built.
3. Downloadable Merkle JSON appears; Merkle root is displayed.

2. Verify Integrity

1. Select Original File and Merkle JSON.

2. Click Verify.

3. View report:

   • Root match (✔️ / ❌)
   • Corrupted chunks count
   • Corruption percentage

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🛠️ Implementation Details

• Chunking: Ensures ≥50 chunks, even for small files.

• Hashing: Base64-encode then SHA-256 hash each chunk.

• Tree Build: Pairwise concatenate hashes; if odd, duplicate last.

• API Endpoints:

  • /upload handles file → returns JSON + root
  • /verify handles file + JSON → returns verification data

• Static Hosting: uploads/ served for JSON retrieval.

• CORS: Configured in index.js.

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📋 Dependencies

Backend

• express
• multer
• cors
• crypto (built-in)

Frontend

• React (via Create React App)
• Fetch API (native)

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🔍 Troubleshooting

• Run npm install in both merkle-backend/ and merkle-frontend/.
• Confirm backend is listening on port 4000.
• Inspect browser console & server logs for errors.
• Verify correct file + Merkle JSON pairing.

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📄 License

MIT License. Contributions welcome—please open issues or PRs!

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