If you need SSH access to your IPFire instance in the cloud, you will have to enable password authentication in the on the SSH settings page.
Make sure to disable access to the Web User Interface and SSH from the Internet after you have set up the system.
Attackers are scanning the cloud with higher intensity than other networks because of a higher likelihood of finding freshly installed, unprotected systems. Often they are successful. Therefore, please only use SSH key authentication and do not leave SSH password authentication enabled.