Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener that encrypts links client‑side and stores ciphertext on the Cronos blockchain, preventing server‑side tracking and data breaches.

Problem

Traditional URL shorteners log user data, track browsing patterns, and can be hacked, compromising privacy.

Outcome

The system achieves privacy by ensuring the server never sees the destination URL, eliminates centralized data storage, and provides censorship‑resistant, immutable storage on blockchain.

Workflow

• Generate a random IV and AES-GCM key in the browser
• Encrypt the destination URL client‑side with Web Crypto API
• Send the ciphertext to a Cloudflare Worker
• Worker writes the ciphertext to the Cronos blockchain via a smart‑contract call
• User accesses the short URL, Worker fetches ciphertext from blockchain
• Browser decrypts ciphertext locally and redirects to the original URL

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source