The article explores how to build an end-to-end encrypted chat application using PubNub and the Seald SDK, providing a robust security solution that surpasses PubNub's native encryption by incorporating advanced key management and real-time access control. PubNub is highlighted as a scalable real-time communication service, while Seald offers an SDK for end-to-end encryption without requiring prior cryptographic expertise. The integration process includes setting up user accounts on both platforms, managing chat rooms, and implementing encryption sessions for message and file security. The text emphasizes the superior privacy offered by end-to-end encryption, particularly in compliance-sensitive scenarios, and details how Seald's encryption model, certified by ANSSI, mitigates key management vulnerabilities often associated with encryption technologies. Additionally, it outlines the steps for managing group chats and user memberships, ensuring data confidentiality and security even in the event of data breaches.