Authentication to SSHd server

Hi guys,

I wanna know if it is possible to force authentication to a OpenSSH
server by a password and by a RSA Key(With a Passphrase on it). In
this manner, it would be impossible for a attacker to brute force just
the password to get credential of the SSH server.

Thanks for your help

The OpenSSH version I use is the Latest Stable Release (4.7)