What is an example of a challenge-response protocol?

• A. Two-factor authentication
• B. Regular password updates
• C. Biometric scanning
• D. Single sign-on systems

Answer: (A)

A challenge-response protocol is a security mechanism that involves the use of a challenge issued to a user, who then must provide a valid response based on that challenge to gain access to a system or service. This process enhances security by ensuring that even if a malicious actor intercepts the challenge, they cannot simply reuse it without the correct response from the legitimate user.

Two-factor authentication often employs this concept by requiring a user to authenticate using something they know (like a password) and something they have (like a code sent to their phone). The code represents a challenge, and the user’s input of the code is the response. This layered approach minimizes the risk of unauthorized access, as it extends beyond simple password entry, reinforcing the identity verification process.

In contrast, regular password updates provide a way to change access controls but do not typically involve a challenge-response dynamic. Biometric scanning focuses more on identity verification using physical traits rather than a challenge-response interaction. Single sign-on systems allow for multiple services to be accessed using one set of login credentials but do not inherently incorporate a challenge-response mechanism for each access attempt. These other options lack the interactive and dynamic nature that defines a challenge-response protocol.