Which certificate field allows a host to be identified by multiple host names or subdomains?

Which certificate field allows a host to be identified by multiple host names or subdomains?

• A. Common Name (CN)
• B. Entropy
• C. Wildcard domain
• D. Subject Alternative Name (SAN)

Answer: (D)

Identifying multiple host names with a single certificate relies on the Subject Alternative Name extension. This extension lets a certificate list multiple DNS names and IP addresses, so one certificate can be valid for several subdomains or different hosts. Browsers validate the hostname against the SAN entries, and while the Common Name field is a legacy place to store a single name, SAN is the mechanism that actually carries the multiple identities today. A wildcard like *.example.com can be used within the SAN to cover all subdomains, but the fundamental concept is that SAN is the field that holds the multiple host names. Entropy is unrelated to host identification, so it doesn’t fit here.

Identifying multiple host names with a single certificate relies on the Subject Alternative Name extension. This extension lets a certificate list multiple DNS names and IP addresses, so one certificate can be valid for several subdomains or different hosts. Browsers validate the hostname against the SAN entries, and while the Common Name field is a legacy place to store a single name, SAN is the mechanism that actually carries the multiple identities today. A wildcard like *.example.com can be used within the SAN to cover all subdomains, but the fundamental concept is that SAN is the field that holds the multiple host names. Entropy is unrelated to host identification, so it doesn’t fit here.