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Death Note Anonymity: L, Anonymity and Eluding Entropy (gwern.net)
99 points by rfreytag on May 15, 2015 | hide | past | web | favorite | 23 comments

Death Note would have been an extremely boring comic if Light had been smart or a bit ruthless. Given how easy disinformation is with a death note, it'd not be hard to hide the fact that he existed for years, and even after someone figured it out, to make it almost impossible to figure out his location. Nobody is getting bits of information about you if they don't know you exist.

So what we get in Death Note is a calamitous lead character that has to make middle schooler mistakes, that then suddenly develops some smarts: It's the only way to make the net grow close early on, but then withstand a few more books. But even with the whole second kira twist and all of that, it's very hard to make the story coherent, and kira not get caught very quickly after making the mistakes that are mandatory to make the story any fun. Ultimately, Ohba has to rely on making L also act in pretty suboptimal ways, just to make the first arc of the story last long.

Which brings us to how Death Note is a good example of why it's so hard to make realistic crime stories: It's very difficult to make a story long enough to not be trivial, and yet have the criminal get caught in the end: It's far easier to make a very good criminal or a hapless one than to make one that will move the story along at a good pace.

As @veridies says, the point of Light's actions in DN is to make the world aware of him as a God. His objective is not merely to have people die, but to let the world know that there exists an entity that is "doing good" and passing righteous judgment, living amongst them and aware of them.

If you consider that a core objective, besides just weeding out criminals, his moves weren't "middle schooler mistakes". It is explicitly addressed in both the show and the manga that he intentionally creates patterns and responds directly to provocations to make L and the detectives aware that he is amongst them and is challenging them. Whether that's a merit-worthy core objective or not is questionable, but to him the whole Death Note would have been meaningless without the ability to parade as a God, and that's what made the plot interesting.

It's possible to have a reasonable story even then, with two stipulations.

First, obviously, that L is at least as good as Light; you can't scale up one side and not the other or you don't have a story.

And second, that Light fundamentally wants to be perceived as a real force, since he's nominally trying to deter crime. Sure, if he acted slowly and randomly, he could appear nearly indistinguishable from random chance, but he wants to send a message. That stipulation is enough to force him to reveal some information, and combined with a sufficiently good L, you'd still have a story.

They actually address this in the comic / show: Light wants people to know he exists. He wants to be seen as a god with the power to smite evildoers, which requires being known to exist. Simply killing criminals covertly wouldn't accomplish his goals.

Indeed. Furthermore, he highlights the killing of Ray Penbar's wife as a "mistake". However, Ray Penbar's wife was literally about to tell L that Light can kill using methods aside from heart attacks.

The fact of the matter remained: when Light wanted to "hide" a death from the Police, he'd use a different method. (Episode 5: Kill by Traffic Accident).

The fact of the matter is, if Ray Penbar's wife actually got the information out to L, then Light would have lost right there and then. He was forced to kill her as soon as she was discovered.

If anything, his mistake was killing the FBI team through Ray Penbar in the episodes earlier. Ray Penbar wasn't suspicious of Light... but when Ray Penbar died then the entire L investigation focused on him.

> Death Note would have been an extremely boring comic if Light had been smart or a bit ruthless.

It would have been a boring manga if one made Light a bit smarter or more ruthless and tried to stick to the same plot, yes. But that just means they could have tried a different plot, and explored a different part of the world: what happens when states react to a Kira and start switching to secret rulers and figurehead leaders? The most plausible explanation for a Kira would be some exotic form of nanotech or biological warfare, so what happens when states begin crash projects into developing their own assassination tools? What happens when Light reasons that criminals are a relatively trivial cause of death and instead kills Kim Jong-il? What's the fallout of that and what risks does he have to take to fix it? Instead of a second Kira being a fan of his, perhaps it could be one with very different goals and it becomes a fairer version of the L/Light duel (you don't even have to change Light's job); and for that matter, instead of being gray and apathetic figures, what if the shinigamis were the real villains all along and Ryuk's gift to Light was a... poisoned apple, one might say?

There's plenty of stories one could tell, and I think Ohba & Obata are more than talented enough to tell those stories without requiring asspulls or idiotballs.

Probably mostly towards the end of getting a good story, two of the behaviors mentioned in this article as erroneous are somewhat intentional (though all the effects aren't). Light specifically mentions that he is making his deaths visible because he wants people to know that there is someone behind it, playing into the idea that he has gained godlike powers and will use them to change the world. He also goes out of his way to bait L to some degree in an attempt to eliminate him, believing L to be the only true obstacle in the way of achieving his end goal. With hindsight this is obviously the wrong move to make (he gave away a lot of information for no good reason), but you can see why someone faced with an invisible enemy might feel like drawing out their opponent is a good idea.

All that said attempting to anonymize his targets probably wouldn't have done him that much good anyway. As a Japanese person his sources of news and information would be at least on some level biased towards hearing about events which have some connection to Japan. Even if he was able to overcome that through the internet, people have a very noticeable habit of treating things physically closer to them as being more real than something on the other side of the world. Adding entropy within a limited information aperture only gets you so fat, I'm pretty sure he would have still had information leaking just through that lone.

Ah "Death Note" one of my Anime favorites of all time, I'm not an Anime zealot but Death Note was my gateway drug into other types of Anime that weren't only action based, truly brilliant.

If you like Death Note I highly recommend Monster, which is a similar not-type anime with a focus on psychology and philosophy. It's one of the most brilliant pieces of writing I've ever experienced.

I am an anime zealot, and Death Note is really high up on my list of "best series"

I find it hard to drive home how much info people leak. Just the cultural references you make, cross referenced with Kindle purchase history...

But as touched on, the real question is how well does disinformation work against LE? We see all sorts of dumb reveals in court documents. A single line like "yeah I spent 30 days in jail for pot last summer" really narrows it down. But how far will it throw LE off if such a slip is false? Are they actively trying to determine this kinda thing? Without knowing how many investigations simply fail, I suppose it's hard to know.

I guess the best indicators are the long-standing evasions we know of, such as the FBI agents that the KGB turned.

The other take-home lesson is to use high-latency communication. In the lulzsec investigations, agents monitored when Tor was on in the suspect's apartment, correlated to when the handle was chatting. (OK he was probably toast at that point anyways.) I'd also guess that doing batch communication reduces the tendency to slip up. No small talk. Also no external interruptions ("sorry, power just went out for a minute") to mention.

A mention isn't even necessary. Imagine being Light getting his source of information from the internet, his ISP has a small incident with a lightning storm and they lose connectivity completely for a few days while things get sorted out. Involuntarily information has just been leaked irregardless of all other protections, the deaths of criminals would have been disrupted. In this situation you would ideally be working to some great latency of days or weak to give a buffer of information. It's talked about in the first few episodes that he works ahead in case of sickness, but it's not mentioned after that, possibly because it means he can't use those events as cover for on the spot murders (which would stand out from week old information based murders).

Maybe it would have made sense to only use week-old information to begin with.

Probably would have been a better idea. Only later in the Anime does he actually need to do things quickly, all the rest really could have waited weeks or even months. That said it wouldn't have made for very interesting watching if he managed to have that much forward thinking all the time.

Well, being a keyboard warrior is easy. ;)

The most implausible part seems to be that L is completely anonymous. He is clearly operating with other people, therefore he leaves a trail of information. Even if he is perfect at covering that up, people working with him aren't.

Light could also use his powers to extort. Someone in the police/media/politics must know who L is. Therefore it would be only a matter of time until you hit a person that knows him. An alternate approach to this, which is contrary to Light's beliefs, is to keep executing important people until L is revealed, someone will reveal him eventually.

If you are look for more fiction, which tries to be "realistic" or as I would say "internally consistent", there is some community on reddit: https://www.reddit.com/r/rational/

This is about "rational" fiction, which is well explained here: http://tvtropes.org/pmwiki/pmwiki.php/Main/RationalFic

Anyone seeing this? https://i.imgur.com/WQMM3Tu.png

The page is unreadable for me. Firefox 38.0.1 on Windows 7. Disabling AdBlock doesn't seem to help.

Firefox 38.0.1, Windows 7 here. Works fine for me.

Try clearing your cache.

"differential privacy is impossible" -- might we have argued after the failure of Enigma in World War II that unbreakable encryption was impossible? Absence of evidence is not very reliable evidence of absence.

> that unbreakable encryption was impossible?

Isn't that still an open question? We have Shor's algorithm which disposes of a bunch of things on its own, and the existence of one-way functions at all remains an assumption rather than a known fact.

Information-theoretically secure encryption and authentication do exist, so in a sense unbreakable (authenticated) encryption is a fact. Outside of that, the existence of OWFs is indeed an assumption, but I doubt anyone's losing sleep over it.

The original argument didn't make sense to begin with: the SIGABA rotor machines used by the US during WW2 were never known to have been broken during actual use, so the only reasonable conclusion about cryptography to draw at the time was that Enigma was simply a poor instance of it.

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