Can I rename the master key or change its content?
No! The master key should be left as it is. if you rename it or change its content it will most probably not work anymore.
Note: the master key is a heavily encrypted file and as such you can't read its (true) content.
If you previously changed your master key name and now it does not work, please contact support for help. Please note that you should not send your master key to support.