Signal and Messaging Layer Security

Signal and Messaging Layer Security is a comprehensive guide to signal protocol. Used by widely deployed messengers such as Facebook Messenger, WhatsApp, Wire, Viber, and many others, Signal has become the standard for end-to-end encrypted (E2EE) communication. Despite its widespread adoption, the protocol remains largely unexplained in security literature. This book fills that gap by providing a clear, accessible explanation of the Signal protocol for security professionals with a basic understanding of cryptography.

Beyond the Signal protocol, the book also addresses the crucial challenge of scaling E2EE messaging to group communication. While Signal was designed for two-party messaging, extending its security guarantees to large groups is a complex problem. The second focus of this book is the Messaging Layer Security (MLS) protocol, currently being standardized by the Internet Engineering Task Force (IETF.) MLS is designed for large-scale deployments, enabling secure group messaging for thousands of participants.

By exploring both Signal and MLS, this book offers a deep dive into the protocols shaping secure communication today. It provides a clear and comprehensive guide to understanding the core principles behind modern E2EE messaging. Readers will gain an understanding of forward secrecy, post-compromise security, and the intricacies of encrypted messaging in both one-on-one and group settings making it an essential resource for anyone working in the field of secure communications.