Change encryption from user to master key


I’d like to change from user-key encryption to master-key encryption.
I think I can ask my users to backup their data, but my

1st question is, is it possible to change without any user issue? I guess not compatible these 2 encryption types.

2nd: The encryption documentation always relates to backup the encryption keys, but I haven’t found anywhere how and what is the process to restore it for the user? “Make sure you have backups of all encryption keys, including those for all your users.”

3rd: How can I change to master-key encryption? I need to disable the encryption module, then enable it back via occ and after select the master key? I’ve tried to play around on my test system, but I wasn’t able to change to master, I’ve disabled encryption, enabled back, disabled the app, enabled back and always got back “User keys already enabled”

Thank you your help.

Like this, it works.