Authentication: Packaging and labeling, Provenance, Two-factor authentication, Chip Authentication Program, Closed-loop authentication, Authorization, CAPTCHA, Diameter (protocol)

Authentication is the act of establishing or confirming something (or someone) as authentic, that is, that claims made by or about the subject are true ("authentification" is a variant of this word). This might involve confirming the identity of a person, tracing the origins of an artifact, ensuring that a product is what its packaging and labeling claims to be, or assuring that a computer program is a trusted one.