JWT Authentication Explained Properly: OAuth, OIDC, PKCE & JWKS for .NET APIs

🔐 JWT Authentication Explained Properly: OAuth, OIDC, PKCE & JWKS for .NET APIs

JWT is one of the most misunderstood concepts in backend development.
Most implementations treat JWT as “authentication”, skip the trust model, and end up with APIs that look secure — but aren’t.

In this video, we walk through a production-grade, end-to-end authentication and authorization flow for modern .NET APIs using OAuth 2.0, OpenID Connect (OIDC), PKCE, and JWKS.

This is not a shortcut tutorial.
It’s an architectural explanation of how authentication actually works in real systems.

📌 What you’ll learn in this video

Why JWT is NOT authentication

The role of the Authorization Server vs the API

OAuth 2.0 Authorization Code flow with PKCE

How JWT access tokens are issued and used

Why APIs validate tokens offline

What JWKS (JSON Web Key Set) is and why it matters

How APIs validate:

Token signature (RS256)

Issuer (iss)

Audience (aud)

Expiry (exp) and validity (nbf)

How claims are mapped to identity in .NET

Where authorization actually happens (roles, scopes, policies)

Common JWT mistakes that break production systems

🔍 Concepts explained clearly
PKCE (Proof Key for Code Exchange)

PKCE protects the OAuth login flow from authorization code interception attacks and is mandatory for SPAs and mobile applications.

JWKS (JSON Web Key Set)

JWKS allows APIs to verify JWT signatures securely using public keys, enabling stateless and scalable token validation.

🧠 Who this video is for

Backend & API developers

.NET engineers working on secured APIs

Developers confused by OAuth vs OIDC vs JWT

Anyone building real-world, production systems

🚫 This video is not an intro to JWT libraries or a copy-paste guide.

⏭️ What’s next

This video is part of a modern .NET security series, where we’ll cover:

OAuth vs OIDC in depth

Service-to-service authentication

API Gateway vs App-level authorization

Common JWT security failures in production

Zero-Trust architecture for .NET APIs

📎 Helpful links & references

OAuth 2.0 Authorization Code Flow

OpenID Connect Core Specification

JSON Web Token (RFC 7519)

JSON Web Key Set (RFC 7517)

🎓 Want to go deeper?

If you’re interested in hands-on, production-grade backend development, feel free to check out my Udemy courses where I cover .NET microservices, Clean Architecture, CQRS, authentication & authorization, distributed systems, and real-world enterprise patterns in depth. The courses focus on why things are designed a certain way, not just how to write code, and are continuously updated to reflect modern .NET practices.

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