Display key fingerprints informations in /var/log/auth.log

If you have multiple users connecting to a single SSH account (ie: root) and you want to identify clearly who's connecting:

Ensure this value in /etc/ssh/sshd_config:

LogLevel VERBOSE

/etc/init.d/ssh restart

Everytime a new SSH connexion is completed you could list the fingerprint used: tail -f /var/log/auth.log

To identify a fingerprint's owner by listing all entries in /root/.ssh/authorized_keys

while read l; do
  [[ -n $l && ${l###} = $l ]] && ssh-keygen -l -f /dev/stdin <<<$l;
done < /root/.ssh/authorized_keys