Hi Pieter,
I advice you not to use ResourceBundle for that purpose. I think you will certainly lose some points because you are abusing (a class from) the
Java API, while there is another class
java.util.Properties that's more suitable for the job.
And as a final remark I think you are just overcomplicating this. How I handled it: the magic cookie is verified against a hard coded value (in my Data class) and I justified that approach in decisions document.
Kind regards,
Roel