Authenticating

Authenticating, or authentication, is the process of establishing the claimed identity of a user, device, or service attempting to access a resource. It answers the question: are you who you say you are? Authentication complements authorization and accounting in access control.

Authenticators are classified by factors: something you know (passwords, PINs), something you have (security tokens, smart cards, mobile devices), and something you are (biometrics). Many systems use multi-factor authentication, combining two or more factors to increase security. Some approaches also consider where the user is or how the access request is made as contextual factors.

Common methods and technologies include passwords, one-time codes, hardware tokens, cryptographic keys, and digital certificates. Biometric verification is increasingly used. Modern web and enterprise systems employ protocols such as TLS with mutual authentication, and identity frameworks like OAuth 2.0, OpenID Connect, and SAML for federated authentication.

Security practices include protecting credentials at rest and in transit, applying multi-factor methods, and using secure session management. While biometrics improve convenience, they raise privacy and revocation issues. Ongoing risk-based checks and user education help mitigate phishing and credential theft.