Help with facial authentication.

Hello, I would like some help with a college project. I'm working on a project that aims to be a facial authenticator.
In this project, I'm using Java as the programming language, IntelliJ as the IDE, and OpenCV as the library.

I've been studying OpenCV and have already managed to do quite a bit with it, like converting images to grayscale, calculating histograms, and facial detection. However, I’m having serious doubts about how to authenticate. Specifically, how can I identify who is appearing on the webcam, and whether or not they have permission to access the system?

Thank you for your attention; any help would be greatly appreciated.