Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener that encrypts destinations client‑side, stores ciphertext on a blockchain, and decrypts locally, eliminating server‑side tracking.

Problem

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

Outcome

A fully functional privacy‑first URL shortener that stores only encrypted URLs on a blockchain, eliminating server‑side tracking and providing 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 to a Cloudflare Worker endpoint.
• Worker writes the ciphertext to the Cronos blockchain as immutable data.
• User receives a short URL pointing to the worker.
• When the short URL is visited, the worker fetches the ciphertext from the blockchain.
• Browser decrypts the ciphertext locally and redirects to the original URL.
• No server logs the destination or user data.
• The system remains censorship‑resistant and has no central database to hack.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source