Fidelius Charm speculation

[sunnyskywalker]

While looking over Oryx's posts on Vold War I, the question of why the Fidelius Charm seemed to be entirely broken by the time Hagrid arrived caught my eye again. Because obviously, anyone can see the house now--it's a graffitied memorial. Hagrid could find it with no problem (he doesn't seem likely to have been on the short list of people let in on the secret in the week it was active), and so could the Muggle emergency services shortly after.

Oryx suggested that the secret ended when its subject ceased to exist, whether that subject was the house or the Potters themselves.

However, the house didn't really cease to exist, except in the sense that having a big hole in one room damages its integrity as a house. Does it work similarly to Horcruxes, where if you damage the subject enough that it doesn't function properly (in this case, as a house), the secret breaks, even if the subject is otherwise mostly intact? This seems like a really bad way to set up the charm: all you'd have to do is figure out the general location and start lobbing small explosives in the right direction. Eventually, one would do enough damage to break the secret. But maybe wizards wouldn't think of that.

Also, making the secret be the Potters rather than the house causes its own problems. You'd have to assume that Harry wasn't part of the secret, most likely, or how would Petunia have been able to see him on her doorstep? But if Voldemort could still see Harry through the window, what would it matter if he couldn't see James and Lily? They don't know Harry is the primary target, but Voldemort taking Harry as a hostage to force James and Lily to reveal themselves should have crossed their minds.

Or maybe the secret was that "the Potters are inside Whatever Cottage in Godric's Hollow," so that they couldn't be seen while in the house, and then Harry could be seen by anyone as soon as Hagrid took him out. That brings us back to Hagrid having been brought into the secret. It couldn't have been by Peter telling him in person (unless Polyjuice was involved), but maybe Peter sent a note. On the other hand, there's still no obvious reason for them to have let Hagrid in on the secret. Unless Dumbledore convinced them that they needed someone on the Hogwarts staff to be a secret-knower for some reason, and they felt Hagrid was the most trustworthy?

However you work it, something always seems off. You can explain it... but it takes work and feels forced.

Here's another possibility, which I haven't fully worked through yet: no one told Harry, but the Secret Keeper isn't restricted to only telling one person at a time. The Secret Keeper has the option of revealing the secret to the world all at once.

After all, suppose the secret needed to be undone quickly for some reason? For instance, if the people inside a Fideliused location needed emergency help and you couldn't contact the Secret Keeper in time to let the rescuers in on the secret? Or maybe you would want whichever bystanders were closest to be able to get in, so breaking the secret for everyone at once would be the quickest method. Or maybe if a person inherited a secret-kept house like Grimmauld Place, they might want to de-secret it at some point when the danger had subsided and their kids wanted to bring friends over without needing to go through a magic ritual first.

Why would Peter have used this option instead of just telling Voldemort the secret, though? If the secret was the house, maybe Voldemort wanted to make sure the world could see his murderous handiwork right away. No point in sending up the Dark Mark to advertise that you've killed your enemies if no one can see anything when they get there.

A smart villain would have waited until after he'd killed his targets, but this is Voldemort. And maybe he had some concern that if he left Peter sitting around, thinking about how he'd betrayed his friends, Peter would try to run off or something before breaking the secret, reasoning that if he left the secret intact, everyone would assume Voldemort just used his mysterious dark powers to get in rather than that the Secret Keeper was a traitor. It should only take him a few minutes to kill them, so he should have plenty of time to get away before whatever alarms Dumbledore might have set brought the Order to the scene.* So the risk was low.

So Peter broke the secret and Voldemort immediately Apparated to the Potters' street (where a kid admired his "costume"). Then he busted in through the front door, killed James, ran upstairs, killed Lily, and failed to kill Harry. Fortunately, the secret being broken meant that Hagrid had no trouble digging Harry out of the rubble before Muggle emergency services arrived.

I'm not sure this works more smoothly than the other possibilities, but at least there's another slightly strained option?

Incidentally, what kind of alarms did Dumbledore have that he knew immediately that (a) James and Lily were dead, (b) Harry wasn't, and (c) he should send Hagrid to take Harry to Little Whinging? Or should we assume time travel shenangigans?

Comments

[chantaldormand]

Generally speaking Potterverse magic isn't mystical (like SW Force), administered by some being (like in many DnD inspired settings), dependant on caster's willpower and interpretation (like in Dresden Files) or semi-sentient. Ironically it works like simple computer algorithm:

If actor does A and B then do C.

This means that in most cases magic would work with dictionary definitions and pick the most straightforward intent, since there is nobody to do interpretation for it.

The phrase I gave as example of password could be reduced to:

'Potter family lives at X'= true/false then 'Fidelius Charm'= true/false

Simple, no room for errors and something Lily and James might come up with.

The problem with Dumbledor's password is the same one we encounter with majority of things he says; just like majority of the readers assumed that "use his proper name, Voldemort" = You-Know-Who's true name is Voldemort, it's quite possible to misinterpret the password.

The devil is in phrase "may be found". It's vague language and it's quite possible that once somebody who knows how the spell works sat down and inspected it they realised there is a possible vulnerability and forced the Order to relocate. I would place my bets on Bill, since he is the next person to use the spell.

As for the whole spawning secret keepers? From outside perspective it's obviously JKR's attempt to retcon things so she can easily push forward plot. From inside perspective it could have been easily a lie that is told to kids and/or Order members so they won't have any stupid ideas.

Another explanation is that after caster's death the spell got weaker and weaker, but I don't think we ever learn who casted it.

[jana-ch.livejournal.com]

I don't think we ever learn who casted it.

I always imagined Dumbledore cast the spell because:
1) He's the leader of the Order.
2) He prefers to keep all important matters under his own personal control.
3) He's generally acknowledged (by himself and his followers) to be incredibly brilliant, incredibly powerful, incredibly skillful at complex magic, and (of course) utterly trustworthy. [insert sarcasm icon]

Canon doesn't actually say one way or the other.

[madderbrad.livejournal.com]

The devil is in phrase "may be found".

Hmmm, maybe. I admire the wriggle room you've found in how 'may' suggests less than absolute certainty but I'm not sure it's enough to get around the true/false pattern matching 'algorithm' you're using.

If one is looking for the HQ then certainly it 'may be found' at GP, so that secret is true, and thus should be hidden.

[chantaldormand]

Hmmm, maybe. I admire the wriggle room you've found in how 'may' suggests less than absolute certainty but I'm not sure it's enough to get around the true/false pattern matching 'algorithm' you're using.

I've considered it for a bit and I came to conclusion that if we use word may we are pretty much introducing an element of randomness to algorithm and this type of algorithm is not as simple as those I used as examples.
In this scenario we have:
While A=true and X≥Y then B
Where:
A stands in for actor knowing the secret
X stands for random number generated via random number generator or rolling 5x 20d dices :P
Y stands value allowing you access. The lower value the higher chance that the spell will allow you entering the HQ
B stand for the spell letting you see the HQ.
Of course this is optimistic approach where FC will only occasionally troll a member of OotP and not for example let random person see the HQ.
In that case we potentially have:
While A=true and X≥Y then B
While A=false and X≤Y then C
While A=false and X>Z then B

C stands for the spell not letting you see the HQ

Obviously it's simplified version of algorithm, but I see no point in complicating things too much.

[dorea-ysleen.livejournal.com]

I agree that the secret no longer existing would generally void a Fidelius, but I think that in case of the Potters, it broke because Peter betrayed them. He was their secret keeper, the one they put their faith (fides) in, and he told the one person they needed protection from most, going completely against the intent of the spell.
(It would mean Voldemort knowing this much about the Fidelius Charm and only having Peter tell him the secret once he was ready to go so the Potters wouldn't have time to notice that something was wrong with their protection, but I don't think that's impossible.)

As to who cast it... the switch in secret keepers was known only to Lily, James, Sirius and Peter. I imagine the bonding of the secret keeper is part of casting the Fidelius, similar to the unbreakable vow, where both parties are present as well as named, so that would narrow it down a lot - to either Lily herself, as has often been speculated because of her Charms talent, or (if she couldn't as one of the subjects to be protected) to Sirius.

[jana-ch.livejournal.com]

You’re right that having the Secret Keeper present means that Dumbledore can’t have cast the Fidelius. Some have suggested that Dumbledore cast it with Peter-Polyjuiced-as-Sirius standing as Secret Keeper, but that adds an unnecessary layer of complication. Besides, I don’t think the Marauders were disloyal enough to go out of their way to deceive Dumbledore. They just left him out because they thought they were so much cleverer than he was, and they had always done things on their own.

It doesn’t feel quite right to me, however, for Lily to have cast the spell, despite her supposed Charms skill (which is based solely on what Olivander says about her wand, not any evidence we see about Lily herself). The whole thing feels to me like an all-Marauder production. No need to get the little woman involved. Sirius is so incredibly talented (just ask him) that he can do it. Lily doesn’t even need to be in the room; Prongs has talked it over with her, and she’s busy with the baby, after all. It’ll be just us three trusted Marauders, like in the old days, out-foxing Voldie like we out-foxed Dumbles.

I can’t present any actual evidence for this. It’s just a feeling on my part, but it sure seems like the sort of thing they would do.

[sunnyskywalker]

That does sound like them, unfortunately. And Lily was probably so exhausted caring for both a toddler and James (an emotional toddler climbing the walls with cabin fever), with no support and little or no contact with her friends or the outside world generally, that she might not have had the energy to argue about something they'd already done or grill them for details about the exact wording they'd used. (Even if you don't posit a James as bad as in Terri's "Liberacorpus," Lily's life those last few months must have been rough. I tend to read her letter to Sirius as desperately trying to convince herself that things aren't so bad, really. Sure, she cries all night sometimes when she hears a colleague has been horribly murdered, but otherwise everything's great, honest! They're a happy family having a mostly-normal life!)

Hm, it also occurs to me that maybe Flitwick called the Fidelius Charm "complex" in part because there are several different ways of casting it, not just because figuring out how to word it and/or the spellcasting itself is complicated. He described it as holding the secret within a single living soul when we learn later that multiple people can hold the secret under certain conditions, so he must have been simplifying for his audience. Maybe all the secret-knowers becoming secret-keepers when the original SK dies isn't the only possibility; it's just that Dumbledore used that version for No.12. Maybe you can also cast it so that it expires when the SK dies, or so that the SK can release it to the world at will, or so that every secret-knower automatically becomes an SK. For instance, maybe that last version is on the Leaky Cauldron, and when Hagrid pointed it out to Harry, he was actually letting Harry in on the secret (after which Harry could have told anyone else). That's weak security, but it would have to be--it's the entrance to a shopping district. Whoever originally cast it might have felt that keeping out a few people people with no personal connection to wizarding Britain was better than nothing. Or maybe it was originally about keeping out hedge witches and cunning folk who hadn't attended Hogwarts, idk.

Point being, if there are different ways to implement it, which did they use? And given how infrequently used the charm apparently is, did whatever they use as their source of information describe all the options fully? Maybe they assumed Magic Wikipedia explained everything, and it didn't. (This is why you don't ignore the footnotes.) Which still makes them overconfident, but slightly less so than if they deliberately ignored potentially better options.

And there's the Peter factor, of course. We know there are magical way of, erm, nudging people into having impaired understanding and judgement. Peter could easily have "nudged" them to a particular option and "nudged" them to feel like it was all their own idea, and a really great idea too. They wouldn't expect the weak toady to Confund them, now would they?

Maybe Peter thought that if he could get them to use a version--either through wording or the spellcasting or both--which would release the secret into the world all at once, everyone would assume Voldemort broke the secret with his Amazing Dark Powers^TM, and Peter would have an easier time getting away with his betrayal if anything went wrong. I mean, it's best to have layers of protections, right? First make sure that they use a version that will make it look like the SK didn't reveal the secret, Voldemort broke it. Then make sure everyone except Voldemort and the intended victims think Sirius is the SK, so not only can Peter give Voldie the secret, but if necessary, it will be easy to frame Sirius and Peter's still covered.