First published: 31st July 2007
From an information security perspective, the latest Harry Potter film left out the most magical part of the book, Harry Potter and the Order of the Phoenix. In the film, Alastor "Mad-Eye" Moody reveals the secret location of the group's headquarters using his staff, but, in the book, Harry has to read a note from Professor Dumbledor before he can become aware of its existence. This is because it is protected by the Fidelius Charm, which, as previously noted prevents transitive betrayal of trust.
Such a Charm could provide the perfect defence against virus spread, make unbreakable DRM, and totally eliminate software piracy. Imagine, you would need to receive a personally-signed license from Bill Gates before you could use Windows, and you couldn't copy or resell the capability! It is the software developer's dream... the nightmare is signing all those licenses.
The power and subtlety of the Fidelius Charm is incredible to anyone who thinks about information flow, and the film, unfortunately, is less magical for having left it out.