Authentifizierungsfaktor

Authentication is the process of establishing and verifying the identity of a user, device, or other entity attempting to access a system. It is the first step in access control and is often described alongside authorization and accounting as part of the AAA framework. Authentication answers the question of whether an entity is who it claims to be and is essential for enabling appropriate access to resources.

Methods of authentication fall into three broad categories: something you know (knowledge-based factors such as passwords or PINs); something you have (possession-based factors such as security tokens, smart cards, or mobile devices for push confirmations); and something you are (inherence-based factors such as biometric identifiers like fingerprints or facial recognition). Modern systems frequently employ multi-factor authentication (MFA), which combines two or more factors to reduce the risk posed by credential theft or misuse. Passwordless approaches increasingly use methods such as biometric verification, hardware tokens, or secure public-key credentials.

Technologies and standards support authentication workflows. Password-based schemes rely on secure storage and hashing of credentials. Public-key infrastructure (PKI) enables certificate-based authentication. Protocols used in modern web and enterprise environments include OAuth 2.0, OpenID Connect, SAML, and FIDO2/WebAuthn, which facilitate single sign-on, delegated authentication, or passwordless sign-in.

Security and privacy considerations include protecting against phishing and brute-force attacks, implementing rate limiting and robust MFA, and managing biometric data with privacy-reserving practices. Authentication operates at various layers, from network-level mutual TLS with client certificates to application-level sign-in, reflecting the diverse approaches used to verify identity in contemporary digital systems.