PubNub SDKs provide capabilities for end-to-end message encryption, allowing developers to encrypt entire or partial message payloads between clients using symmetric keys, such as AES-256. The architecture for implementing this encryption involves generating a unique per-conversation key for secure messaging between users, which can be rotated as needed. Users must register and authenticate before exchanging messages, and different encryption approaches can be used, including server-trusted and zero-trust methods. Key management and distribution can be handled via cloud services like AWS, utilizing tools like AWS KMS and Lambda for key generation and storage in DynamoDB. The encryption process ensures that keys are never stored or transmitted in plaintext, maintaining end-to-end encryption. While the article focuses on symmetric encryption, it notes the possibility of implementing asymmetric encryption with PubNub, albeit without built-in support in the SDK.