Which authentication factor refers to information or a code you already know?

The knowledge factor refers to information or a code that an individual already knows, such as passwords, PINs, or answers to security questions. This factor is foundational in many authentication systems, as it relies on the user's ability to recall and input specific information that is intended to remain private and secure. This method provides a way to verify identity based on something the user possesses mentally, unlike other factors that might rely on physical attributes or items.

In terms of the other factors: possession refers to something the user has, such as a smart card or a mobile device with an authentication app. Inherence refers to an individual’s unique physical or behavioral characteristics, such as fingerprints or facial recognition. Location factor involves the physical location from which a user is attempting to authenticate, which does not pertain to knowledge that one possesses. The distinction makes the knowledge factor unique and crucial in many authentication scenarios.