When logging in, an administrator must use a temporary six-digit code that is displayed on a key fob. Which of the following has been implemented?

Biometrics involves using unique biological characteristics like fingerprints or facial recognition for authentication, not temporary codes.

HOTP (HMAC-based One-Time Password) is an event-based OTP algorithm that generates a new one-time password based on a shared secret key and a counter. When implemented with a key fob, the fob contains the shared secret and increments the counter, displaying the resulting code for user authentication.

PKI (Public Key Infrastructure) uses digital certificates and public/private key pairs for authentication and encryption, not a six-digit code from a key fob.

A software token generates OTPs on a device like a smartphone using an app, while a key fob is a dedicated hardware device.