Comprehensive and Detailed
This scenario describes an enterprise VPN setup that requires machine authentication before a user logs in. The best explanation for this requirement is that the VPN client selects the appropriate certificate automatically based on the key extension in the machine certificate.
Understanding the Key Extension Requirement:
PKI (Public Key Infrastructure) issues machine certificates that include specific key usages such as Client Authentication or IPSec IKE Intermediate.
Key usage extensions define how a certificate can be used, ensuring that only valid certificates are selected by the VPN client.
Why Option B is Correct:
The VPN automatically selects the correct machine certificate with the appropriate key extension.
The process occurs without user intervention, ensuring seamless VPN authentication before login.
Why Other Options Are Incorrect:
A (MFA requirement): Certificates used in this scenario are for machine authentication, not user MFA. MFA typically involves user credentials plus a second factor (like OTPs or biometrics), which is not applicable here.
C (Wi-Fi connectivity before login): This refers to pre-logon networking, which is a separate concept where devices authenticate to a Wi-Fi network before login, usually via 802.1X EAP-TLS. However, this question specifically mentions VPN authentication, not Wi-Fi authentication.
D (SSL VPN with certificates): While SSL VPNs do use certificates, this scenario involves machine certificates issued by an internal PKI, which are commonly used in IPSec VPNs, not SSL VPNs.
Reference:
CompTIA SecurityX CAS-005 Official Study Guide: Section on Machine Certificate Authentication in VPNs NIST SP 800-53: Guidelines on authentication mechanisms