Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener that encrypts URLs client‑side, stores them on the Cronos blockchain, and decrypts them in the browser, eliminating server‑side tracking.

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.

Outcome

Cryptly provides a privacy‑first URL shortener where no server logs user data, the data is stored immutably on a blockchain, and decryption occurs entirely in the browser, eliminating tracking and single points of failure.

Workflow

• 1. User enters a URL in the Cryptly web interface.
• 2. The browser generates a random IV and derives an AES‑GCM key.
• 3. The URL is encrypted with Web Crypto API and the IV.
• 4. The encrypted payload is sent to a Cloudflare Worker.
• 5. The Worker writes the encrypted data to the Cronos blockchain via a smart contract.
• 6. The Worker returns a short code to the user.
• 7. When the short code is visited, the Worker fetches the encrypted payload from the blockchain.
• 8. The browser decrypts the payload locally and redirects to the original URL.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source