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 and single points of failure.

Problem

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

Outcome

The system delivers a URL shortener that never sees destination URLs, removes tracking, and stores data on a tamper‑proof blockchain, providing privacy and censorship resistance.

Workflow

• 1. User enters a URL in the web interface.
• 2. Client‑side JavaScript generates a random IV and AES‑GCM key.
• 3. The URL is encrypted with Web Crypto API and the IV.
• 4. The encrypted payload is sent to a Cloudflare Worker.
• 5. The Worker writes the encrypted data to the Cronos blockchain via a transaction.
• 6. The Worker returns a short code derived from the transaction hash.
• 7. User shares the short link (e.g., https://cryptly.workers.dev/abc123).
• 8. When the link is visited, the Worker fetches the encrypted payload from the blockchain.
• 9. The browser decrypts the payload locally using the same key and IV.
• 10. The browser redirects to the original destination URL without exposing it to any server.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source