Disabling password authentication for SSH doesn't work as expected Ubuntu 14.04 LTS

I want to make sure that the only way to access a computer through SSH is if the client's key is already added to the `authorized_keys` file on the server. For this, I edit `/etc/ssh/sshd_config` and enable the following options ``` ChallengeResponseAuthentication no PasswordAuthentication no PubkeyAuthentication yes UsePAM no ``` Following this, I restart the `sshd` service ``` sudo /etc/init.d/ssh restart ``` However, when I try to ssh into the server from a client whose key is not saved in the server's authorized keys file, I get prompted for a password. EDIT: I have figured out what the problem is, but I am going to leave this question here in case it is useful to someone else. What happens is that when connecting from a client with a key not in the `authorized_keys` file, the server asks for the password, but no matter what password is entered, it is declined. I think this is so that it is difficult for attackers to understand how the sshd is configured.