What is the biggest mistake made by the killer killer Kira of the manga `` DEATH NOTE '', and it becomes like this when analyzing L's reasoning in terms of information science

by Clarence Risher

The cartoon `` DEATH NOTE '' by Tsugumi Ohba and Ken Obata drawn the battle of Yagami Kazuki with Death Note that can kill the person who wrote the name and L, the world's best detective This work is so popular that it can be developed into animated , live - action movie , and drama . In the first part of such DEATH NOTE, Mr. Gwern Branwen, a freelance writer, analyzed from the viewpoint of information science what kind of mistake Kayatsuki Yayozuki who called `` Kira '' and murdered has been caught up by L Is doing.

Death Note: L, Anonymity & Eluding Entropy-Gwern.net

Kira's crimes are global, and at first, Kira's suspects who did not appear anonymously were all 7 billion people. Since 7 billion is approximately 2 to the power of 32.7, L's anonymity means that L initially has approximately 32.7 bits of information. “This is a search issue and can actually be treated as a basic information theory,” says Branwen. On top of that, he argues that the Moon lost anonymity by making the following five mistakes:

◆ 1: Killing method
Branwen points out that the fundamental mistake of the moon is to kill in a way unrelated to the goal. A person whose name is written on Death Note will die of a heart attack unless specified with the cause of death specified. The death was incredibly accurate, indicating that something very anomalous was happening, and it was an early relief of Kira's existence.

by zerobaek0100

◆ 2: When to kill
In addition, the moon uses Death Note to kill someone, but this killing is by no means random and tends to occur at certain times. Since there is a time difference on the earth, it is possible to narrow down the countries where the glittering lurking to some extent depends on the active time. Branwen argues, “This mistake allowed L to narrow down the killer from 7 billion to 128 million. Anonymity is lost by about 6 bits.”

◆ 3: Provocation of L
In the early stages of the work, Moon responded to the provocation of L. L. Taylor, L's shadow warrior, and killed Taylor, who killed Kira in a live broadcast. Due to the sudden crime of the moon, L speculated that 'Kira lives in the Kanto region' and narrowed it down to one-third of the Japanese population. According to Branwen, L can be said to have slashed Kira's anonymity by about 1.6 bits through this provocation. However, the male population in Kanto is about 21.5 million, and the moon still has anonymity of log 2 21.500000 ≒ 24.36 bits.

◆ 4: Use of police information
The month was stealing confidential police information using the qualification information of the father of the National Police Agency. Branwen pointed out that the biggest mistake for the month was accidentally revealing his connection to the police by hacking his father's PC. “Assuming that about 10,000 people were suspected of this mistake, the anonymity information would be about 13.29 bits. About 11 bits of anonymity is lost compared to the third mistake. ''

by Michael Miller

◆ 5: Murder of Ray Pember and his fiance
The month killed FBI investigator Len Pember, who was monitoring himself, and his fiancée Naomi Nanami. By killing Pember's fiancée, L becomes suspicious of the moon that was Pember's target. It was the first offense for the moon that killed non-villains, but 'it can be said that the murder resulted in the loss of 6 bits of anonymity, assuming that the suspects were limited to 200,' Branwen points out. “Kira's anonymity is less than 8 bits, and at this point, the game is over,” he concluded.

In this way, after seeing the mistakes the moon made until it was almost specified by L, Branwen verified 'what the moon should have done' and added counterfeit information to increase anonymity It is necessary. For example, if there is 100-bit independent information, and five of them are randomly altered, the anonymity of about 26 bits will be restored.

by tofuprod

Therefore, the following three points are proposed as specific answers: “Timing of killing, style, randomization of target”.

・ Decision execution time is determined using dice.
• The choice of cause of death is randomly determined based on demographic data.
・ Criminals to be killed should be based on periodicals accessible to almost all people around the world, such as the New York Times, and killing criminals only published on Japanese TV Should be avoided.

Lastly, Mr. Branwen introduced the question of an acquaintance, “Why isn't Yagamitsuki an encrypted assassination market?” And said, “Well, that story is not“ DEATH NOTE ”.”

in Manga, Posted by log1i_yk