You can the OpenSSH CA and put on the needed places.
For an usual OpenSSH client, put the following line into $HOME/.ssh/known_hosts 
@cert-authority * ssh-rsa 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
There is also a shell script, which helps you to configure a server and sent a certificate signing request of the public key of the server to the OpenSSH CA.
You can your SSH public key (as .pub file)