Blender Studio uses Blender ID to authenticate users.
The Blender ID is a unified login system that will give you access to a large number of services around Blender. With just one account you can set up a Blender Studio subscription, or a Blender Development Fund membership, manage your BFCT application, Blender Conference talks, your purchases on the Blender Store.
You can also authenticate within Blender via the Blender ID add-on, and log in authorized third-party websites and much more.
For any issue or request regarding your Blender ID, such as merging accounts or fixing an invalid email address, get in touch with blenderid at blender.org. We will help you right away!