Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener where client‑side encryption stores data on a blockchain, preventing server‑side tracking and single points of failure.

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 if the database is hacked.

Outcome

The system achieves a privacy‑first URL shortener where the server never sees destination URLs, no tracking or analytics are performed, and data is stored on a censorship‑resistant blockchain, eliminating a single point of failure.

Workflow

• Generate a random IV and AES‑GCM key in the browser.
• Encrypt the target URL with Web Crypto API using the key and IV.
• Send the encrypted payload to a Cloudflare Worker endpoint.
• The Worker writes the encrypted data to the Cronos blockchain via a smart contract.
• When a user visits the short link, the Worker fetches the encrypted payload from the blockchain.
• The browser decrypts the payload locally with 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