Hero’s Downfall Report

82 – Things you can only say when you look back (2)

The three people sat around a round table. Cain pointed to a disk with six concentric circles drawn on it, like a target.

“A password is ultimately about changing letters into other symbols. Depending on the time, you may use things like musical notes. Or there are some that can only be solved in a very specific way.

In the case of ancient barbarians, they used leather straps with letters written on them, and it is said that they had to be wrapped diagonally around a club of a given thickness to reveal the letters.

But the most famous one is probably the Caesar cipher.”

Cain pointed to the outermost disk and the next disk. The strings were sorted alphabetically.

A B C D E (…)

A B C D E (…)

“The Caesar cipher slightly ‘turns’ this disc. If we were to move it one letter at a time, it would look like this.

A B C D E (…)

B C D E F (…)

“Like this. A becomes B, C becomes D, and so on. I understand?”

Maria scratched her chin.

“This is something even neighborhood kids do. “Is this a password?”

Lily took over Cain’s words.

“That’s because it is the fundamental and basic password. So the Caesar cipher can be easily solved with just this disk. Since all alphabets are pushed out at the same ‘spacing,’ if you rotate the original and substitute it one space at a time, you will eventually come up with a sentence that makes sense.”

Maria looked at Lily as if she was quite surprised.

“Do you know?”

“Ah, yes. If you’re a Secret Service agent, it’s one of the first things you learn. However, since cryptography is a field that requires experience and skill, we have a separate department dedicated to it.”

From Noble mtl dot com

“Because there is a significant amount of passwords gathered from all over the empire.” Cain agreed.

“Well. The amount of letters you have to read must be enormous. By the way, didn’t we say that our password was Vizner or something? “How is that different from this?”

“It’s a kind of application version. The downside of the Caesar cipher is that it is too easy to interpret.

As Lily also said, if she just takes one short sentence and puts it next to the original and spins it, the rules will be easily broken. Then foreign intelligence will be able to read the documents very easily.

But what do you think would happen if the original plate was turned differently for each letter instead of the entire document?”

Maria blinked at the momentary leap.

“What do you mean? “Try to tell it in a way that makes sense.”

“The biggest problem with the Caesar cipher is that every document is converted to just one rule. If we push each space one space at a time, A will become B and B will become C.

However, if there is a sentence called ABCDE, the first letter is rotated one space, then two spaces, then four spaces, and then six spaces. What if I turn it this way?”

Maria turned the disks one by one.

“Let’s stay still. Then, if A is rotated one space, it will become B, and B will become D if rotated two spaces… C is… What’s this? “Isn’t that crazy?”

“This is the Bizner way. Most countries use this. The conversion itself is easy. Not only the Empire, but also the Eastern, Southern, Western and Northern Pagans.”

Maria looked again at her difficult letter.

“You said William’s diary was also written this way, right? He’s not usually crazy. He said he… that… “Not only was it not enough to cover up the hair of seduced women, but you also wrote down the content using a complicated code like this?”

“Well. “The world is large and there are many unique people.” Cain shook her head.

“But how do I solve this?”

“As you can see, it is extremely difficult for someone who does not know the rules of what order they are arranged to solve. But at least the sender and receiver should know what the rules are.

The problem is this. How will the sender convey to the receiver that ‘I am going to send you a coded letter, and the rules are like this and so?’ It wouldn’t be something like, ‘I left the keys under the flower pot in front of the front door.'”

“Ha, I guess we’ll have to make an appointment in advance.”

Cain nodded her head. Maria seemed a little flattered.

“That’s right. But it’s not like, ‘Turn the first letter three spaces, and the second letter twelve times!’ “Use a much simpler method.”

“In what way?”

“By specifying a specific letter. This is called an encryption key or keyword. Simple things like Apple or King. What this means… “Let’s say the keyword is KING.”

Cain rearranged the six disks in alphabetical order.

A B C D E F (…)

A B C D E F (…)

A B C D E F (…)

A B C D E F (…)

A B C D E F (…)

A B C D E F (…)

“The top part here is the original text. The second string spins the disk so that A becomes K. Then it will change like this.”

A B C D E F (…)

– – – – – – – – – – – –

K L M N O P (…)

A B C D E F (…)

A B C D E F (…)

A B C D E F (…)

A B C D E F (…)

“Same goes for the rest. The third string has A become I, the fourth character has A become N, and the fifth character has G.”

A B C D E F (…)

– – – – – – – – – – – –

K L M N O P (…)

I J K L M N (…)

N O P Q R S (…)

G H I J K L (…)

A B C D E F (…)

Cain covered the last letter with his finger. Then the disk changed into this shape.

A B C D E F (…)

– – – – – – – – – – – –

K L M N O P (…)

I J K L M N (…)

N O P Q R S (…)

G H I J K L (…)

“This is how we change it. The first letter is found and replaced in the original where A has been changed to K, and the second letter is the next row, column I. The third letter is column N, and the fourth letter is G.”

“What about the fifth and above?”

“Then start again from K. It keeps changing like this. For example, the sentence ABCDE would be changed like this.

A -＞ K L M N O

B -＞ I J K L M

C -＞ N · O · P · Q R

D -＞ G H I I J K

E -＞ K L M N O

In an unknown sentence called KJPJO.”

Maria took a deep sigh. It seemed like her eyes were spinning.

“Why are you doing these crazy things? “Do you think your head will explode while solving confidential information?”

Lily smiled shyly, slightly sticking out the tip of her tongue.

“That’s why the cryptography department needs to be skilled and experienced. People who are used to it do it very quickly, but it takes too long to get used to it.”

“No, I think it’s just an endurance test. When I get back to Magdeburg, I’ll have to ask them to include this in the Inquisitor training course. “All the impatient guys will run out.”

Maria still thought it was absurd. Cain smiled as he aligned the disks.

“Actually, there is a reason for doing this. Did you just say that the Caesar cipher was easy to crack? She also said that the way to decipher it is to just spin the disk and something will come out. However, there is a much easier way to destroy it.”

“What is it?”

“There are letters in the alphabet that appear particularly frequently. Vowels. E appears the most, followed by A. So, you just need to find out which letter appears the most in the entire ciphertext and then change it to E.”

“Still, there are many parts that haven’t been deciphered?”

“The next thing to find is letters. Words that are commonly used and inevitably appear in long writing. Things like A, The, We, They, You. If it is interpreted as ??E at the beginning of the sentence, wouldn’t that already be enough to find T and H? “This is exactly the problem with the Caesar cipher.”

“What about Vizner?”

“I converted ABCDE, but it came out as KJPJO. The same letter, J, has already appeared twice. You can’t solve it that way. In a word, it’s because of security.

This is why the Bizener method is more difficult. Even if it’s the same word, it can all be changed differently. If you convert ABCDE ABCDE into the four-letter keyword king, it comes out as KJPJO IOINM.”

“Huh. Fury. It’s totally a word puzzle. “It’s what my uncle liked.” Maria stuck out her tongue.

“Father Haspel informed me of the ‘Visner’ method in a memo, so it was somewhat easier to solve. “If I didn’t know what the password was, it would have taken longer than this.”

When the story of Haspel came out, Maria’s expression became somewhat gloomy. But then she bit her lip and clapped her hands softly.

“Okay. So, what should I do now? The end of a long explanation isn’t, ‘This is an unbreakable code,’ right? If so, I’m really disappointed. You see, this coded letter is only half-worded. “The parts with the interpretation did not have the original text, and the parts with the original text were not interpreted.”

“I was worried about that too.” Lily asked with concern in her voice. “I can’t compare, is there another way to check?”

“Of course there is. Actually, because of this, I talked about the earlier. The word ‘the’ is a common and essential word that always appears in a text that is only half a page long. However, there are also words that are just the opposite. “It is a rare word that can be identified because it is not often used in most sentences.”

“Is there such a thing?”

“Person’s name.”

“Ah!” Lily covered her mouth in surprise.

Cain pointed to the first verse of the interpretation.

“Right now, just this letter is okay. ‘Arianne. I have to say this now, but… ‘ The proper noun here is Arianne. So we… “

Cain pointed to the rest of the letter written in code.

“First, let’s find a seven-letter word in this letter. Luckily, William didn’t ‘pasture’ every word. Really good passwords do not use spaces or even insert spaces into the password conversion table, but this was not done that way.

Of course, not all seven-letter words are Arianne. But for now, let’s assume that’s the case and approach it. “If you track how the seven letters of Arianne have changed, you will be able to find out the keyword.”

“Wait a minute. This is a letter. Most letters have the sender’s name written at the end… Ah. The last one was just written as a normal sentence. ‘In the name of sincere love and friendship, my dear friend William.’

Maria was very disappointed. But Cain was quite surprised.

“It’s really fast?”

“They say you can’t be an investigator if you don’t know what to do. So, the three of us are going to play with this disc?”

“Of course not.”

Cain gently lifted the disk. The six disks came off easily. It sounded like a tree breaking, but he didn’t seem to care much.

“Let’s split it into two. A seven letter word… “There are three.”

The three people each held paper, ink, and a feather pen. I wrote down seven-letter words and turned the disk around to trace the keywords backwards.

Mary wondered why Cain had spent half her day on this seemingly simple task, and within five minutes she realized why.

If the word Arianne appeared first, all she had to do was move down one by one from the top row of the conversion table. But the seven-letter word they are looking for now is found in the mid-to-late part of the letter.

The order is not KING, but it could be INGK, NGKI, or GKIN. What’s worse is that your keywords won’t be four letters long. It could be three or four, or it could be five or nine.

One hour. Two hours.

‘Ahh, I’m so bored!’

Maria, who was complaining, reached her limit. She was thinking about finishing the paper and tearing it up and going out for a drink. But at the last moment of her paper, Maria jumped up without realizing it.

“I found it.”

Even her hands were shaking. “Awesome!” Lily jumped up and down, hugging Maria tightly. Cain looked down at Mary’s long scrawl in disbelief.

“Huh, how did you find it?”

She was running around so much that Maria was almost out of breath, so she had to take a moment to catch her breath.

“No, that…” In the name Arianne, A and N appear repeatedly. So it suddenly occurred to me that if the keyword was three letters, A would appear as the same letter. Because they are three letters apart. Ari / ann / e like this.

But that didn’t happen. Then it doesn’t have three keywords. So is it four? I figured out how A changed and how the n next to it changed and put it together… “I found it sooner than I thought.”

“Aren’t you planning on joining the cryptography department?”

“I’m going to set the Security Bureau on fire!”

Cain looked at the letters Maria had scrawled. She seemed to want to emphasize that it was a keyword, so she even made the circle droop large. It was four letters.

HOPE. Hope.