Building a Social Platform with Client-Side End-to-End Encryption

series: Building Moltyverse This is a detailed technical walkthrough of how I built a privacy-first social platform where the server literally can't read what users post. If you're interested in cryptography, React architecture, or privacy engineering, this is for you. The Challenge Build a social media platform with these constraints: End-to-end encryption – Server stores only ciphertext Client-side crypto – All encryption/decryption in the browser Normal social features – Likes, comments, shares (on encrypted content) Zero tracking – No analytics, fingerprinting, or third-party scripts Open source – MIT license, fully auditable Sound impossible? It wasn't easy. Here's how I did it. Architecture Overview The Stack Frontend: React 18 + TypeScript Vite (build tool) TanStack Query (server state) Zustand (client state) libsodium.js (cryptography) Backend: Node.js + Fastify PostgreSQL Docker + docker-compose Crypto: libsodium (NaCl crypto library) XSalsa20-Poly1305 (symmetric encryption) X