Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener that encrypts links client‑side and stores ciphertext on the Cronos blockchain, keeping servers blind to destinations and protecting against data breaches.

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 provides a privacy‑first URL shortener where the server never sees the destination URL, eliminating tracking and reducing the risk of data breaches, while leveraging blockchain for censorship‑resistant storage.

Workflow

• Generate a random IV and AES‑GCM key in the browser.
• Encrypt the destination URL with Web Crypto API.
• Send the ciphertext to a Cloudflare Worker.
• The Worker writes the ciphertext to the Cronos blockchain via an API call.
• When a user visits the short link, the Worker fetches the ciphertext from the blockchain.
• The browser decrypts the ciphertext locally using the same key and IV.
• The browser redirects to the original URL without exposing it to any server.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source