Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener using client‑side encryption and storing ciphertext on the Cronos blockchain, eliminating data collection and central points of failure.

Problem

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

Outcome

The system achieves privacy‑first URL shortening with immutable storage, no centralized database, and censorship resistance.

Workflow

• Generate a random IV and AES‑GCM key in the browser.
• Encrypt the destination URL with Web Crypto API.
• Send the ciphertext and IV to a Cloudflare Worker endpoint.
• Store the ciphertext on the Cronos blockchain via the worker.
• When a short URL is visited, the worker fetches the ciphertext from the blockchain.
• The browser decrypts the ciphertext locally using the same key and IV.
• Redirect the user to the decrypted URL.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source