CryptoVault — Encryption Demonstration System

A full-stack web app demonstrating Symmetric (AES-256-CBC) and Asymmetric (RSA-2048-OAEP) encryption, built with Node.js + Express on the backend and pure HTML/CSS/JS on the frontend.

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Folder Structure

crypto-demo/
├── backend/
│   ├── server.js          # Express API (AES + RSA endpoints)
│   └── package.json
├── frontend/
│   └── public/
│       └── index.html     # Complete single-file frontend
├── package.json           # Root convenience scripts
└── README.md

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Installation & Running Locally

Prerequisites

• Node.js v18+ — Download here
• A terminal (VS Code integrated terminal works great)

Step 1 — Install backend dependencies

cd crypto-demo/backend
npm install

Step 2 — Start the backend server

node server.js
# OR for auto-reload during development:
npx nodemon server.js

You should see:

 CryptoDemo API running on http://localhost:3001

Step 3 — Open the frontend

Open frontend/public/index.html directly in your browser.

Tip in VS Code: Right-click index.html → Open with Live Server (if you have the Live Server extension). Or simply double-click the file to open it in your default browser.

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🔌 API Endpoints

Method	Endpoint	Description
POST	/api/symmetric/generate-key	Generate AES-256 key + IV bundle
POST	/api/symmetric/encrypt	Encrypt message with AES key bundle
POST	/api/symmetric/decrypt	Decrypt ciphertext with AES key bundle
POST	/api/asymmetric/generate-keys	Generate RSA-2048 key pair
POST	/api/asymmetric/encrypt	Encrypt message with RSA public key
POST	/api/asymmetric/decrypt	Decrypt ciphertext with RSA private key
GET	/api/health	Health check

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Sample Test Inputs

Symmetric (AES-256)

1. Click Generate Secret Key — copy or download the key bundle
2. In the message box, type:

   Hello World! This is a secret AES message.
   

3. Click Encrypt Message — you'll get a Base64 ciphertext like:

   kV3Xz9P2mN8...==
   

4. Switch to Decrypt tab
5. Paste the ciphertext and the key bundle
6. Click Decrypt Message → original message restored ✅

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Asymmetric (RSA-2048)

1. Click Generate Key Pair — download BOTH keys
2. In the message box, type (keep it ≤190 chars):

   Secret RSA message — only the private key holder can read this!
   

3. Click Encrypt with Public Key — you'll get a long Base64 ciphertext
4. Switch to Decrypt tab
5. Paste the ciphertext + paste/upload your private key
6. Click Decrypt Message → original message restored ✅

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❌ Testing Wrong Key (Error Handling)

• Encrypt a message with one key
• Try to decrypt with a different key
• You'll see: ❌ Decryption failed. Wrong key or corrupted data.

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Security Design Decisions

Feature	Detail
No auto-fill keys	Keys are never stored or auto-populated in decrypt fields
AES-256-CBC	Industry-standard 256-bit symmetric encryption
RSA-2048-OAEP	Secure asymmetric encryption with SHA-256 hash
IV per session	Random initialization vector generated with each key
Key isolation	Server never stores any keys; they exist only in memory per request

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Features

• ✅ AES-256-CBC symmetric encryption/decryption
• ✅ RSA-2048-OAEP asymmetric encryption/decryption
• ✅ Download keys as .txt files
• ✅ Copy-to-clipboard for all values
• ✅ Drag & drop key file upload
• ✅ Encrypt / Decrypt tab toggle
• ✅ Dark mode UI (always on)
• ✅ Input validation with descriptive errors
• ✅ Character counter for RSA messages
• ✅ Loading states on all async operations

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Dependencies

Backend

Package	Purpose
express	HTTP server & routing
cors	Cross-origin requests from frontend
node-forge	Available if needed for additional crypto

Note: The app primarily uses Node.js built-in crypto module (no external crypto lib needed for core functionality).

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Troubleshooting

Problem	Solution
Cannot connect to API	Make sure node server.js is running on port 3001
CORS error	Ensure you're opening the HTML from a browser (not an iframe restriction)
RSA message too long	RSA can only encrypt ~190 bytes directly; shorten your message
Decryption failed	You likely used the wrong key — keys must match exactly
Port conflict	Edit PORT in server.js and update API constant in index.html