What is Authentication?

Authentication is the process of verifying that someone or something is who or what they claim to be. It's a fundamental security control that precedes authorization and is essential for access control.

Authentication Factors

Knowledge Factors Something you know:

Passwords
PINs
Security questions

Possession Factors Something you have:

Hardware tokens
Mobile devices
Smart cards

Inherence Factors Something you are:

Fingerprints
Facial recognition
Voice patterns
Iris scans

Behavioral Factors Something you do:

Typing patterns
Gait analysis
Usage patterns

Authentication Methods

Password-Based

Traditional passwords
Passphrases
Password managers

Token-Based

TOTP/HOTP
Hardware tokens
Software tokens

Certificate-Based

PKI certificates
Smart cards
mTLS

Biometric

Fingerprint
Face ID
Voice recognition

Modern Approaches

Passwordless authentication
Passkeys (FIDO2/WebAuthn)
Risk-based authentication
Continuous authentication