Learn how to allow specific users to authenticate using a password, whilst everyone else has to authenticate via a key file instead.
This tutorial will show you how you can configure Docker to safely use a remote Docker host, by simply configuring SSH details, rather than having to set up any kind of fancy TLS security.
Create a GitHub deploy key in order to give your pipelines restricted access to just one project.
Learn how to store secrets / credentials in Jenkins.
See just how easy it is to create keys for your services that have limited access rights. This could save your bacon.