Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener that encrypts links client‑side, stores them on the Cronos blockchain, and decrypts them in the browser, eliminating server‑side tracking.

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 achieves a privacy‑first URL shortener where the provider never sees destination URLs, no central database exists, and the data is censorship‑resistant.

Workflow

• 1. User enters a URL in the client UI.
• 2. Client generates a random IV and AES‑GCM key, encrypts the URL with Web Crypto API.
• 3. Encrypted payload is sent to a Cloudflare Worker.
• 4. Worker writes the encrypted data to the Cronos blockchain as a transaction.
• 5. Worker returns a short code (transaction hash or derived ID).
• 6. User shares the short link (e.g., https://cryptly.workers.dev/abc123).
• 7. When the link is visited, the Worker fetches the encrypted payload from the blockchain.
• 8. Browser decrypts the payload locally using the same key and IV, revealing the original URL.
• 9. Browser redirects to the destination URL without the server learning it.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source