Implementing Two-Factor Authentication

C.

The correct answer is C. Smart card.

Two-factor authentication (2FA) is a security mechanism that requires two forms of identification before granting access to a system or service. These two factors are usually something you know (such as a password) and something you have (such as a physical device). The goal is to make it harder for unauthorized users to gain access to sensitive information or systems.

Out of the options given, the most appropriate choice for 2FA is a smart card. A smart card is a physical device that contains a chip with information about the user. It may require a PIN or passphrase to be entered in addition to the card itself. The user inserts the smart card into a reader, and the information on the card is used to authenticate the user.

Here's why the other options are not as good as smart cards:

• PIN: A PIN (Personal Identification Number) is a numeric password used to authenticate a user. While it is a form of authentication, it only provides one factor of authentication (something you know), which is not sufficient for 2FA.
• Security question: Security questions are used as a way to reset passwords or gain access to an account if you forget your password. They are not a reliable form of authentication as the answers can often be guessed or found through social engineering.
• Passphrase: A passphrase is a longer, more complex version of a password. While it can be a good way to secure an account, it only provides one factor of authentication (something you know), which is not sufficient for 2FA.
• CAPTCHA: A CAPTCHA is a test used to determine if a user is human or a bot. While it can help prevent automated attacks, it is not a form of authentication and does not provide any additional security beyond preventing automated attacks.

Therefore, the best option for implementing 2FA is to deploy smart cards.