Building a Privacy-First URL Shortener on Blockchain

Description and use

Cryptly is a privacy-first URL shortener using blockchain. It employs client-side AES-GCM encryption via Web Crypto API with storage on Cronos blockchain. The server never sees destination URLs.

Problem

Traditional URL shorteners like bit.ly log user IP addresses, timestamps, user agents, track browsing patterns, and sell this data to advertisers. Their centralized databases are also vulnerable to hacks.

Outcome

Cryptly provides a privacy-preserving URL shortener where the server never sees destination URLs, eliminating tracking, analytics, and centralized data storage vulnerabilities.

Workflow

• User encrypts destination URL using Web Crypto API (AES-GCM) in browser
• Encrypted URL is stored on Cronos blockchain
• When shortened link is clicked, browser fetches encrypted data from blockchain
• Browser decrypts URL locally using stored key
• User is redirected to destination without server ever seeing the original URL

Evidence

Server never sees destination URLs - No tracking, no analytics - No database to leak - Censorship-resistant (blockchain)

Source

const encrypted = await crypto.subtle.encrypt({ name: "AES-GCM", iv: iv }, key, urlBuffer);

Source