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 locally, eliminating server‑side data collection.

Problem

Traditional URL shorteners log user data, track browsing patterns, and can be hacked, exposing sensitive information.

Outcome

Cryptly provides a URL shortener that never exposes destination URLs to servers, offers censorship resistance, and eliminates a single point of failure.

Workflow

• 1. User enters a URL in the Cryptly web interface.
• 2. The browser generates a random IV and derives an AES‑GCM key.
• 3. The URL is encrypted with Web Crypto API and the ciphertext is sent to a Cloudflare Worker.
• 4. The Worker writes the ciphertext to the Cronos blockchain via a smart‑contract transaction.
• 5. The short link (blockchain transaction hash) 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 navigates to the decrypted URL without exposing it to any server.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source