If I'm not mistaken it's actually a hash of the file's signature that you have to register, not a hash of the file itself. And Bootmgr will not allow you to cha

If I'm not mistaken it's actually a hash of the file's signature that you have to register, not a hash of the file itself. And Bootmgr will not allow you to change its signature. Thus any computer that is configured to boot Windows with secure boot will be able to boot any copy of Windows.