Building a Privacy-First URL Shortener on Blockchain

Description and use

Building a privacy‑first URL shortener using client‑side encryption and Cronos blockchain storage, ensuring the server never sees the destination URL and eliminating tracking and single points of failure.

Problem

Traditional URL shorteners log user data, track browsing patterns, and sell data, creating privacy risks and single points of failure.

Outcome

Cryptly provides a privacy‑first URL shortener where the server never sees the destination URL, eliminating tracking and single points of failure while leveraging blockchain for censorship‑resistance.

Workflow

• 1. User enters a URL in the client UI.
• 2. The browser generates a random IV and derives an AES‑GCM key via Web Crypto API.
• 3. The URL is encrypted client‑side and the ciphertext is sent to a Cloudflare Worker.
• 4. The Worker writes the ciphertext to the Cronos blockchain as immutable data.
• 5. The short link is returned to the user.
• 6. When the short link is visited, the browser fetches the ciphertext from the blockchain.
• 7. The browser decrypts the ciphertext locally using the same key and IV, revealing the original URL.
• 8. The browser redirects to the decrypted destination without exposing it to any server.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source