How to make authorization through a certificate (file)?

Question

PHP

Hello!
There is a task: user registration, but in such a way that during registration a file (certificate) is issued, with which it will be possible to log in to the user. How can this be done as safely as possible?

Answer 1

Yuzay nginx
https://habr.com/post/213741/
Make a submenu like clientarea.site.com and ask for a certificate there.
You can release through php through a wrapper to openssl