Building a Privacy-First URL Shortener on Blockchain

Description and use

The author built Cryptly, a privacy-first URL shortener using Cronos blockchain and client-side AES-GCM encryption. This prevents tracking and data leaks, as the server never sees the destination URL.

Problem

Traditional URL shorteners like bit.ly compromise user privacy by logging IPs, timestamps, user agents, and destination URLs, tracking browsing patterns, selling data to advertisers, and maintaining centralized databases vulnerable to hacking.

Outcome

A privacy-first URL shortener named Cryptly was created, ensuring that destination URLs remain encrypted until decrypted locally in the user's browser, eliminating server-side tracking and central database vulnerabilities.

Workflow

• Client-side encryption of the destination URL using AES-GCM via the Web Crypto API.
• Storage of the encrypted URL on the Cronos blockchain for immutable, decentralized record-keeping.
• Browser fetches the encrypted data from the blockchain.
• Local decryption of the URL in the browser using the Web Crypto API.
• Redirection to the destination URL without the server ever processing the final link.

Evidence

Server never sees destination URLs

Source

Encrypted URL stored on Cronos blockchain

Source

Live demo: cryptly.workers.dev

Source