Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener built with client‑side encryption and Cronos blockchain storage, ensuring the server never sees the destination URL and eliminating centralized data collection.

Problem

Traditional URL shorteners log user data, track browsing patterns, and sell data, creating privacy risks and a single point of failure.

Outcome

The system provides a privacy‑first URL shortener where the server never sees the destination URL, eliminates centralized data storage, and offers censorship resistance.

Workflow

• 1. User enters URL in the web form.
• 2. Client‑side JavaScript generates a random IV and AES‑GCM key.
• 3. The URL is encrypted with Web Crypto API and the ciphertext is sent to a Cloudflare Worker.
• 4. The Worker writes the ciphertext to the Cronos blockchain via a smart‑contract call.
• 5. The Worker returns a short code (hash) to the user.
• 6. When the short code is visited, the Worker fetches the ciphertext from the blockchain.
• 7. The browser decrypts the ciphertext locally using the stored key and redirects to the original URL.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source