Two-Factor Authentication (2FA) and Passkey Authentication in ASP.NET Core
Modern web applications must protect user accounts from password theft, phishing, and credential-stuffing attacks. Two-factor authentication adds a second verification step beyond passwords, while passkeys offer passwordless login via FIDO2/WebAuthn public-key cryptography. This article explains why 2FA matters, how ASP.NET Core Identity supports email, SMS, and authenticator app TOTP flows, setting up recovery codes, comparing 2FA versus passkeys, implementing passkey registration and login with Fido2.AspNet, and security best practices for production authentication systems.