Ssh configuration

enable encrypted ssh authentication

$ mkdir ~/.ssh
$ chmod 700 ~/.ssh

copy public keys from another host

$ vim ~/.ssh/authorized_keys

Force key authentication only

$ sudo vim /etc/ssh/sshd_config
 PermitRootLogin no              # << Changed to prohibit root login over ssh
 PasswordAuthentication no       # << This toggles the ssh key only authorization
 ChallengeResponseAuthentication no      # changed to force key auth. only
 UsePAM no                       # << Changed to set ssh key authorization only