Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener built with client‑side encryption and blockchain storage, eliminating server‑side data collection and providing censorship resistance.

Problem

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

Outcome

Cryptly demonstrates a privacy‑first URL shortener that eliminates server‑side data collection, protects against database hacks, and offers censorship resistance via blockchain storage.

Workflow

• 1. User enters a URL in the client UI.
• 2. The browser generates a random IV and AES‑GCM key using Web Crypto API.
• 3. The URL is encrypted client‑side and the ciphertext is sent to a Cloudflare Worker.
• 4. The Worker writes the ciphertext to the Cronos blockchain as immutable data.
• 5. The Worker returns a short code (e.g., a hash or index).
• 6. User shares the short link (cryptly.workers.dev/<code>).
• 7. When the short link is visited, the Worker fetches the ciphertext from the blockchain.
• 8. The browser decrypts the ciphertext locally with the stored key and redirects to the original URL.
• 9. No server logs or analytics are collected.
• 10. The system remains censorship‑resistant and privacy‑preserving.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination URLs

Source