Building a Privacy-First URL Shortener on Blockchain

Description and use

Cryptly is a privacy‑first URL shortener that encrypts links client‑side and stores them on the Cronos blockchain, ensuring the server never sees the destination URL and no user data is tracked.

Problem

Traditional URL shorteners log user data and can be hacked, exposing sensitive browsing information.

Outcome

Cryptly provides a privacy‑first URL shortener where the server never sees the destination URL, no tracking data is collected, and the data is stored immutably on a blockchain, reducing the risk of data breaches.

Workflow

• Generate a random IV and AES‑GCM key in the browser.
• Encrypt the destination URL with 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.
• The server never sees the plaintext URL or user data.

Evidence

Bit.ly logs your IP, timestamp, user agent

Source

Encrypted URL stored on Cronos blockchain

Source

Server never sees destination

Source