Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener where the client encrypts URLs, stores them on the Cronos blockchain, and the server never sees destinations, eliminating tracking and database leaks.

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 achieves a privacy‑first URL shortener where the server never sees destination URLs, no tracking occurs, and data is stored on a censorship‑resistant blockchain.

Workflow

• 1. User enters URL in the client UI.
• 2. Browser generates a random IV and AES‑GCM key.
• 3. URL is encrypted with Web Crypto API.
• 4. Encrypted payload is sent to a Cloudflare Worker.
• 5. Worker writes the encrypted data to the Cronos blockchain.
• 6. Worker returns a short code to the user.
• 7. When the short code is visited, the Worker fetches the encrypted data from the blockchain.
• 8. Browser decrypts the payload locally and redirects to the original URL.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source