Day 6 of 13 Authentication in .Net

Build secure cookie-based authentication from scratch in .NET Core. Includes Data Protection, secure cookie flags, sliding expiration, custom events, and best practices.

Sukhpinder Singh

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5 min read

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Sep 27, 2025

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Table of Contents

1. Introduction
2. Understanding Cookie Authentication
3. Setting Up Cookie Authentication
4. Implementation Details
5. Security Considerations
6. Advanced Scenarios
7. Best Practices
8. Troubleshooting

Introduction

Cookie-based authentication is one of the most common authentication mechanisms for web applications. In ASP.NET Core, it provides a stateful authentication approach where user credentials are validated once, and subsequent requests are authenticated using a secure cookie.

When to Use Cookie Authentication

• Traditional web applications with server-side rendering
• Applications where users expect…