Which identity proofing method combines something a user knows, like a password, with an ownership-based smart card or biometric identifier?

The identity proofing method that combines something a user knows, such as a password, with an ownership-based smart card or biometric identifier is Two-Factor Authentication (2FA). This concept enhances security by requiring two forms of verification: one that the user knows (like a password) and another that they possess or can provide (like a smart card or biometric data).

Utilizing this dual approach significantly reduces the risk of unauthorized access since an attacker would not only need to know the password but also require physical access to the second factor of authentication. This layered security model is a critical aspect of protecting sensitive information in various systems, as it mitigates the chances of vulnerabilities associated with using single-factor authentication.

In contrast, other methods listed do not fit this dual requirement for security. For example, Time-Based One-Time Passwords (TOTP) serve as a form of one-time authentication code but do not incorporate the aspect of ownership or possession in the same way as 2FA. Similarly, out-of-band mechanisms involve a secondary communication channel for verification but are focused on the delivery method rather than combining different types of authentication factors. Diameter is a protocol for authentication and accounting but does not specify a method of identity proofing. Therefore, 2FA stands