In authorized key, if we put from option, only the listed host can come to this host. Even if we put the private key in different location, only
host1, host2 and host3 can come from my example? Is this host based access control?
The sshd server can globally limit which hosts can connect to this machine by using TCP Wrappers, but cannot act on a host-user level. Using the from option, you can allow a given identity to be used only from specific hosts. Hosts are separated by commas, may contain wildcards "*" and "?", or may disallow hosts that are prefixed with "!". As an example, you may have