Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy-first URL shortener built on blockchain that encrypts URLs client-side, stores them on Cronos, and never exposes destinations to the server, eliminating tracking and data breaches.

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

Users can create and use short URLs without exposing destination URLs to the server, eliminating tracking and reducing risk of data breaches, while benefiting from blockchain’s immutability and censorship resistance.

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.
• Store the encrypted payload on the Cronos blockchain via a Cloudflare Worker.
• When a short link is accessed, the worker retrieves the encrypted data from the blockchain.
• The browser decrypts the data locally with the same key and IV.
• Redirect the user to the decrypted URL without exposing it to the server.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source