Certificate based authentication on Linux

You can create your own certificate and use it in order to authenticate on Linux machines while connecting through SSH. But be aware that SSHD (SSH daemon is the one that accepts SSH connections, and can be perceived as SSH server) is very sensitive to file permissions. If you set wrong permissions on .ssh or .ssh/authorized_keys, your certificate won't work. Here are the correct file permissions (considering that you're in home folder of remote machine target user):

$ chmod 0700 .ssh
$ chmod 0600 .ssh/authorized_keys