How to disable public key authentication in SSH
SSH in most system by default allow login using public key. While this is convenient, it is a security risk when unauthorized person manage to get the private key, especially when the key is not protected by any passphrase. The option to allow public key authentication is PubkeyAuthentication in the /etc/ssh/sshd_config configuration file.
In order to disable public SSH key authentication, Edit configuration file and change this settings.
Reload SSH service
To have the changes take effect, the SSH daemon need to reload the edited configuration file with the following command;