Potter and Security

J. K. Rowling’s books about the young wizard, Harry Potter, come under the critical eye of security analysis. Encouraging people to think, even in an area where the author is not an expert, is surely a useful function of literature.

The discussion on transitive betrayal of trust is wrong to put forwards the death of Harry’s parents as an example. Sirius Black did not make Peter Pettigrew the Potter’s Secret Keeper, he persuaded the Potters to do so – the trust was direct, the advice was flawed. In fact, the Fidelius Charm appears capable of entirely preventing transitive betrayal of trust – in the “Order of the Phoenix”, Snape and Kreacher are unable to name the location of the Order’s Headquarters. Even more astounding, Voldemort’s followers are unable to deduce its location from the facts that Kreacher has seen certain Order members, and Kreacher is a house elf, normally limited to a single location, that some of Voldemort’s followers have undoubtedly visited previously. The power of the charm is demonstrated in the scene when Harry arrives at the Headquarters – until the Secret Keeper tells him the location, it simply does not exist for him.

Fred Cohen notes that limited transitivity is one of the three perfect defences against computer viruses. Limited transitivity is also a requirement of unbreakable DRM. A working Fidelius Charm would therefore be extremely valuable.