What is a purpose of an SSH host key?

Question

Options

• AIt must be sent by any SSH client in addition to a user key in order to identify the client's host.
• BIt is root key by which all user SSH keys must be signed.
• CIt provides the server's identity information to connecting SSH clients.
• DIt authenticates any user that logs into a remote machine from the key's host.
• EIt is used by system services like cron, syslog or a backup job to automatically connect to remote

• A
  5% (2)
• B
  2% (1)
• C
  76% (32)
• D
  2% (1)
• E
  14% (6)

Explanation

SSH host keys serve as the server's digital identity card, allowing clients to verify they're connecting to the legitimate server and not an impostor - this is the foundation of SSH's protection against man-in-the-middle attacks. When you first connect to a server, your client stores its host key fingerprint; on subsequent connections, SSH warns you if that fingerprint changes.

Why the distractors are wrong:

• A is backwards - clients do not send the host key; the server presents it to the client
• B is fabricated - SSH has no hierarchical PKI where user keys must be signed by a root host key
• D confuses host keys with user authentication; host keys identify the machine, not authorize users
• E describes SSH key-based automation for service accounts, which uses ordinary user keys, not host keys

Memory tip: Think of the host key as the server's "passport" - just as a passport proves who you are to border control, the host key proves which server you are to connecting clients. The mnemonic Host key = Host identity helps distinguish it from user keys, which handle user authentication.

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