Be sure to already have a working public/private key ssh login setup. Otherwise you’ll be locked out after activating this changes!
Change the following config parameters in /etc/ssh/sshd_config to read as:
ChallengeResponseAuthentication no PasswordAuthentication no UsePAM no
Restart sshd. Have fun. Stay more secure.
Is your SSHd listening on the default port (22/TCP)? Ever thought about changing ssh to listen to some random port? It’s easy!