Which mechanism constitutes a time-based password that changes at regular intervals?

• A. System validates against a database of known strong passwords
• B. Software notifies password expiration
• C. Microprocessor programmed with an algorithm generates a new and unique password every 60 seconds
• D. Internal algorithm responds to a network authentication software-issued challenge

Answer: (C)

Time-based one-time passwords (TOTP) are generated by a token that runs an algorithm using the current time, producing a new and unique password at fixed intervals. Because the output depends on the synchronized time, the code changes regularly—every minute or 60 seconds in this case. This is a common method for two-factor authentication: you have a device or app that continually replenish a fresh credential that the system can verify using the same secret key and time-based algorithm.

The other options describe different mechanisms. Verifying against a database of static passwords does not produce a changing code. Notifying password expiration merely alerts the user and does not create a new password. A challenge-response process relies on responding to a server-issued prompt, not on a time-driven code that updates at regular intervals.