Building a Privacy-First URL Shortener on Blockchain

Description and use

A privacy‑first URL shortener that encrypts links client‑side, stores them on the Cronos blockchain, and decrypts locally, eliminating server‑side tracking and centralized data storage.

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 that never exposes destination URLs to servers, removes centralized tracking, and leverages blockchain for immutable, censorship‑resistant storage.

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.
• Worker writes the ciphertext to the Cronos blockchain via a smart contract.
• When a user clicks 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 metadata.

Evidence

Bit.ly logs your IP, timestamp, user agent

Source

Encrypted URL stored on Cronos blockchain

Source