MLS protocol overview

XMTP enables secure, end-to-end encrypted communication between identities that can produce a verifiable cryptographic signature.

XMTP implements Messaging Layer Security (MLS), which is designed to operate within the context of a messaging service. As the messaging service, XMTP needs to provide two services to facilitate messaging using MLS:

• An authentication service
• A delivery service

The identity system provides authentication. The self-hosted backend provides ordered storage and delivery. The SDK handles encryption, identity checks, topic construction, cursors, and retries.

Use this section to understand security, envelope types, topics, epochs, intents, cursors, and identity.