How to Build a Secure React Native Chat App with End-to-End Encryption

Building secure chat applications with end-to-end encryption (E2EE) ensures that only the intended participants can read the conversations, with even the service provider remaining blind to the content. This guide details implementing E2EE in a React Native chat app using Stream's infrastructure, leveraging a combination of public-key cryptography and symmetric encryption for strong security. It involves setting up a backend with Node.js, configuring a frontend with React Native, and using libraries like `@noble/curves` for elliptic curve cryptography, `expo-secure-store` for key storage, and `stream-chat-expo` for chat functionalities. The chat system uses Elliptic Curve Cryptography (ECC) for key generation, Elliptic Curve Diffie-Hellman (ECDH) for key exchange, and AES-256-GCM for message encryption and decryption. While E2EE ensures message privacy and security by preventing third parties from accessing the content, it poses challenges in moderation and observability, requiring developers to adopt new approaches such as client-side filtering and metadata-based heuristics for maintaining app integrity.