"GNAP Explained: The Next‑Gen Authorization Protocol and How to Implement It" Modern authorization is no longer “just OAuth with a few tweaks”—it’s a security- and operations-critical system spanning clients, authorization servers, resource servers, and user interaction across devices. This book is for experienced engineers and architects who need to build or modernize delegated authorization for real API ecosystems, and who want a threat-driven understanding of what GNAP enables, what it demands, and how to implement it without inheriting the failure modes that plague existing deployments. You’ll learn GNAP from the specification suite outward: how to read the RFCs, negotiate capabilities, and implement the complete grant transaction lifecycle (requests, interaction, continuation, issuance, and error behavior) as a durable state machine. The book goes deep on access-rights modeling and enforceable policy, decoupled consent and anti-phishing binding, and replay-resistant API access with proof-of-possession, key proofs, token formats, and safe rotation. Practical chapters translate the protocol into production AS/RS architecture, including RS Connections, introspection, abuse resistance, and interop testing with negative cases. Expect hands-on design guidance, operational playbooks, and migration strategies for coexistence with OAuth stacks. Familiarity with HTTP APIs, applied cryptography concepts, and production security engineering is assumed; OAuth knowledge is helpful but not required.