Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener built with client‑side encryption and decentralized storage on the Cronos blockchain, eliminating data collection and providing censorship resistance.

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

Cryptly delivers a privacy‑first URL shortener that eliminates server‑side logging, removes a single point of failure, and offers censorship resistance by storing encrypted URLs on a public blockchain.

Workflow

• 1. User enters a URL in the Cryptly web interface.
• 2. The browser generates a random IV and derives an AES-GCM key via Web Crypto API.
• 3. The URL is encrypted client‑side and the ciphertext is sent to a Cloudflare Worker.
• 4. The Worker writes the ciphertext to the Cronos blockchain as a transaction.
• 5. The short link (blockchain transaction hash) is returned to the user.
• 6. When the short link is visited, the browser fetches the ciphertext from the blockchain via the Worker.
• 7. The browser decrypts the ciphertext locally using the same key and IV, revealing the original URL.
• 8. The browser redirects to the decrypted URL without exposing it to any server.

Evidence

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source