Learn to implement OAuth2 and OpenID authentication flows from scratch in this live-coding conference talk at Devoxx. Move beyond complex diagrams and theoretical explanations to gain hands-on understanding of these essential web protocols for authentication and authorization. Follow along as fundamental concepts are demonstrated through practical coding examples in common programming languages like Python, Java, and JavaScript. Build a complete Single Sign-On (SSO) implementation without relying on existing libraries, gaining deep insights into the core primitives and mechanisms that power these ubiquitous security protocols. Master the practical foundations needed to better utilize OAuth2 libraries in your own applications through this hands-on demonstration.