Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener that encrypts links client‑side and stores them on a blockchain, preventing server‑side tracking and data breaches.

Problem

Traditional URL shorteners log IPs, timestamps, user agents, track browsing patterns, and sell data, creating a privacy nightmare and central database vulnerability.

Outcome

A fully functional, privacy‑first URL shortener that stores only encrypted URLs on a blockchain, eliminating server‑side tracking and central data breaches.

Workflow

• 1. User enters a URL in the client UI.
• 2. Client generates a random IV and AES‑GCM key using Web Crypto API.
• 3. Client encrypts the URL buffer with the key and IV.
• 4. Client sends the encrypted payload to a Cloudflare Worker endpoint.
• 5. Worker writes the encrypted data to the Cronos blockchain via a smart contract or storage API.
• 6. Worker returns a short code to the user.
• 7. When the short code is accessed, the Worker fetches the encrypted payload from the blockchain.
• 8. The browser decrypts the payload locally with the stored key, revealing the original URL.
• 9. Browser redirects to the decrypted destination URL without exposing it to the server.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination URLs

Source