Buckling the split-finger fist cuff and not forgetting to hang the headset for talking on his left ear, Mitsuki Kaihara symbolically shook his upper body to make a dodge movement, and then swung a few punches in the air as a warm-up.

"Continue with the afternoon topic."

"Hey, you're too desperate, boy."

"That's because you've never seen what a real chase is like. Those who really chase and fight will chase after them to the land of legends (Canaan) for a trivial matter that seems trivial to others. ”

He said as he adjusted his breathing. When he was about to get to the point, he suddenly threw a series of punches and punches into the sandbag, causing it to shake continuously. Maintaining a certain amount of exercise every day is almost his daily homework. He didn't have been involved in the school's football training for long today before he was stopped, and now he intends to make up for this missing part of the exercise.

People who are really familiar with Mitsuki Umihara are often frightened by his enthusiasm beyond ordinary people. He's just a guy who can't be idle, trying to do something at all times, and doesn't even want to waste a minute, even making people think that someone is chasing him.

"I remember telling you that the media that recorded Alice's papers is no longer in my hands, and I have nothing else to say."

The other party complained.

"You should at least have seen it, though. I don't want to know in detail, I just want you to tell me more or less what you remember. ”

He still insisted.

Undoubtedly, this is somewhat different from his previous attitude towards the world. In the eyes of most girls, he has always been very personable, so close to asking a girl who should be about the same age as himself, at least beyond most people's imagination. Even he felt that this was not his intention. It's just that after he weighed it carefully, he felt that it was a matter of no choice.

Although he didn't mean to boast, he did feel that he knew how to deal with women. It's not amazing to say at all, but because he can always accurately judge what he looks like in the eyes of the other party, so he can respond appropriately, so he has always been very popular among girls. In fact, the so-called demeanor is just a simple look at the dishes on the basis of this judgment.

But the person he was talking to at this time, although it was only a verbal conversation, confused him.

The initial conversation made him feel that the person he was talking to must be hiding something. But when he roughly saw through her true identity, the girl's performance made him feel somewhat surprised. At first, he thought it was someone who was good at disguise. But now, it feels as if this is not the case.

What kind of girl is this? It doesn't seem to be her own at all, and her words and deeds are even out of touch with her subjective will.

Aside from his own mother, it was the first time he had dealt with such a tricky woman.

If you can't find the right way to deal with it, simply use the most straightforward method.

Of course, he was also mentally prepared for the other party not to answer, and even imagined the possibility of hanging up the phone directly.

“……”

But for some reason, he was responded to by a long silence.

What exactly is the other party hesitating about? It's a bit overwhelming.

"Do you know anything about cryptography?"

After waiting for a long time, the other party asked.

Since it is not a refusal, it undoubtedly means that there is a play. And the question itself also illustrates the fact that the author of the paper mentioned by the other party should indeed be the Alice mentioned by the mother.

"I'm not very good at it, but I've rarely heard of it, and I know a little bit about classical codes like Gematria."

"Then maybe you'll be a little more understandable than I am. You know that most cryptosystems inevitably have the concept of a key. Of course, the key comes in many forms, it can be a word, a book, or even a piece of music, but in any case, it must be a source other than the message itself, which is known to both the sender and the receiver. Just as the ancient Hebrews used the Bible as their key book. ”

"That's true."

Then, all cryptosystems can simplify their concepts and analyze them fundamentally, which is nothing more than the following parts. 1. A limited amount of possible information. 2. A limited number of possible ciphertexts. 3. A limited number of ciphertexts used for the conversion of the two above. If you draw a picture, it should start from the source of the information, and the message is encrypted by the encrypter and sent to the decryptor. In this process, the key source must also be sent to both the encrypter and the decryptor, which is the method of deciphering and interpreting the ciphertext. In the words of the paper, it is something that will inevitably or perhaps happen when Alice sends the cipher to Bob. ”

Mitsuki Haihara's brows tightened.

The structure of the other person's narrative is obviously very similar to the structure of sending and receiving messages that the mother introduced to her brother and sister in the afternoon. Of course, this is no coincidence, they are essentially the same concept.

Mitsuki Umihara doesn't care about this, but the "Alice" mentioned in this passage.

From the contextual analysis, the Alice mentioned by the other party should not be the author of the paper, but a convention in cryptography. This type of name also refers to the beginning of the English letter of the name. The closer the opening letter is to Z, the lower the probability of this character appearing......

(Huh?) ）

Thinking of this, he suddenly realized a problem.

At Alice's grave, the flowers that her parents "planted" in her honor don't seem right.

It's hard to read in Japanese, but "Alice" and "Iris" are two completely different words. In my mother's words, it is the degree to which errors can easily occur without introducing redundancy of error correction in the spoken mind. Could it be that the parents are using a similar pronunciation to commemorate this friend? Or is it deliberately blurring the two?

There is no doubt that his parents have an amazing knowledge of passwords and information. Think along this line of thought -

Oddly enough, he remembered his mother saying that his father used to make jokes about Alice's name when she was still alive. But after her death, her parents remembered her in the name "Iris", what happened?

Regardless of whether Alice's real name is "Alice" or "Iris", "Iris" does not take the historical meaning of the Greek word "messenger", purely from the perspective of cryptography, the initial I of this name should correspond to Ivan ("Ivan", publisher) or Isaac ("Isaac", Internet service provider).

What kind of considerations did the parents choose to use irises as the burial place of that Alice?

"Go on."

Keeping the thought in his head for the moment, he urged.

"Don't rush me, boy. Even I need to remember the content...... By the way, one of the main points of those papers was a name called 'Mallory', which is a part of my memory that comes up more often. ”

Mallory, if it had been yesterday, Mitsuki Umihara might have really mistaken the name for someone else. However, after making up some of the concepts of cryptographic terms, he knew that it meant something else.

"Mallory", in cryptography, is an attacker. Unlike eavesdroppers, who are referred to as "Eve", Eve passively eavesdrops on messages without changing the content of them. But Mallory is different, he changes so that the content of the message itself changes, and he is a reference to a person who falsifies information.

One of the main points of Alice's paper is the tampering of information by third parties, which should at least be certain.

"I know that 'Eve' is usually treated as a reference to the environment in quantum cryptography, so what is Mallory referring to here?"

It's a concern, isn't it? If the natural environment is regarded as the first and second party, then can the capable person be said to be very similar to "Mallory"?

“……”

Suddenly, the other party fell silent again.

"What's wrong?"

"Ha, do you think I'm a god? I'm not good at this kind of subject in the first place, so it's hard enough to remember that, okay? I'm just a custodian after all, so I don't have to know much about it, do I? ”

This sounds really reasonable, so Mitsuki Haihara didn't have anything to say for a while.

"But, if you think about it, there's another word that comes up a lot in those papers — yes, the word 'Legion.'"

“Legion？ Corps? ”

"No, that's not what it means. It's just a play on words, an abbreviation, similar to 'Advanced_Electronic_Guidance_Information_System', where 'Legion' is an abbreviation for 'Latent_Essential_Garbled_Information_Of_Nod'. ”

Boom!

The sandbag made an unusual cracking sound.

The sandbags, which had been shaking during the hit, stopped swinging almost instantaneously. Fine grains of sand poured out from one side, and the entire sandbag seemed to turn into a huge hourglass.

It was at this time that-

The door to the gym was opened a little from the outside. Mitsuki Kaihara quickly hung up the phone and turned in the direction the door opened.

Today, at night, when the entire parents and the chaotic students who were working were gone, there were only two people left in the family.

Cautiously leaning out of her body, the familiar girl quietly looked into the room.

It's obviously in your own home, but sometimes it seems so restrained. This reminded Mitsuki Umihara of the embarrassing incident that happened when she first became a member of the family because she accidentally broke into her parents' room.

The girl had apparently just taken a shower, her long hair still had a lot of moisture, and her soft body exuded the faint fragrance of liquid glycerin soap. She is also wearing fluffy and light summer pajamas, and her graceful and soft curves are faintly visible, and she is almost cute like a doll.

The overly outstanding appearance makes people feel unreal, as if they were created in a dream.

No matter how many times I watched it, I thought she was too beautiful. Moreover, it is too soft.

Mitsuki Umihara shrugged casually and asked a question jokingly.

"'Latent_Essential_Garbled_Information_Of_Nod', what is the first thing that comes to mind for you?"

I don't really want my sister to give any answer.,It's just a casual search for a topic in a too soft atmosphere.。

Dome tilted her head, as if for a moment she didn't understand what he meant. Just as Mitsuki Umihara wanted to touch her head to bring up the topic, she suddenly opened her thin lips and knitted a word.

“Theory_of_Groups？”

The moment he heard this word, Mitsuki Haihara had a feeling that countless soft thorns rolled through the bottom of his heart.

It seems unrelated, why did she think of this mathematical term? Judging by her confused expression, even she didn't know why she thought of the word.

Besides, why do you feel as if you have picked up some kind of debris?

Before he could think, all of a sudden, the whole earth shook violently.

(Earthquake?) ）

In normal times, earthquakes will not cause any trouble to his sister, who is good at telekinesis, or his sister, who can control gravity freely. However, now that the Dome was forbidden to use her abilities, the violent shaking made her unsteady for a while. Seeing this, Mitsuki Kaihara hurriedly reached out to hug her body.

"Huh?"

My sister seemed to snort a little dazedly, and for some reason her pretty little face gradually became red. Even Mitsuki Umihara himself was baffled by her strange reaction.

It wasn't until after the earthquake stopped that he found out why.

What came from the palm of his right hand was undoubtedly the softest fullness he had ever known.

"Ah...... That ......"

When he came back to his senses, Mitsuki Haihara hurriedly withdrew his hand and retreated, but accidentally stepped on the fine sand that was scattered all over the ground. This shouldn't have been a problem for him, but because of his momentary panic, his whole body fell backwards. Fortunately, the gym is covered with soft rubber non-slip mats, otherwise I am afraid that there will be some problems.

The result was a tragedy for either of their siblings.

Qiong Nai, who was sitting on the ground, and Guanggui, who sat up again, couldn't help but laugh at the same time because he always felt that the other party looked a little ridiculous. The awkward atmosphere before was thrown out of the clouds.

=====================================================

Note 1: An ancient Hebrew mysticism. Letters are used to represent numbers, and words that are sufficient to represent the same number must be related to each other. They use the substitution of numbers-letters to make all sorts of metaphors, and even use them to make prophecies. The most famous example of this is Babylon's relationship with the lion, which is even recorded in the Bible as a prophecy of Babylon's demise. The Bible, especially the Old Testament, is full of such coded scripts, and can even be said to be a model of writing in ciphers. It is generally believed that the Hebrew cipher system is one of the earliest mathematical ciphers of mankind.

Note 2: Advanced_Electronic_Guidance_Information_System, the full English name of the "Air Warning and Ground Integration System" is abbreviated as "Aegis", that is, the famous "Aegis" system of the US military. The abbreviation itself also comes from the cryptographic system, which was very common in the era when the telegraph was mainstream.

PS: This year's change of season is too abrupt, and the result of the sudden drop in temperature is a cold. And then what's even worse is that it actually turned into pneumonia, and this time it was really offended.