Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener that encrypts URLs client‑side, stores them on a blockchain, and never exposes the destination to the server.

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 encrypts URLs client‑side, stores them immutably on a blockchain, and never exposes destination URLs to the server.

Workflow

• Generate a random IV and AES-GCM key in the browser.
• Encrypt the destination URL client‑side using Web Crypto API.
• Send the ciphertext to a Cloudflare Worker endpoint.
• Store the ciphertext on the Cronos blockchain via the worker.
• When a user visits the short link, the worker fetches the ciphertext from the blockchain.
• The browser decrypts the ciphertext locally and redirects to the original URL.
• No server logs or analytics are collected.
• The system remains censorship‑resistant and tamper‑proof.

Evidence

Encrypted URL stored on Cronos blockchain

Source