106. Five on seventy seven
After finishing the night-time surveillance work, I returned to my office and lay down, but I don’t think I can sleep easily.
I checked the time on my watch.
5:10 in the morning.
under—! If I close my eyes now, I can sleep even for 50 minutes… .
The CW cipher text (the cipher text sent by Morse signal) that I received just before the end of work kept me interested.
what? This awkward feeling?
read at noblemtl.com
Naturally, the CW text I received cannot be deciphered.
The numbers of the CW text could not be read using the random number table used for the South Korean random number broadcast that was deciphered a while ago.
In fact, it was thanks to hints from senior soldiers that I was able to decipher a random number broadcast against South Korea a while ago.
When you listen to a random number broadcast, two or three digits continue to appear, and these numbers indicate the location of the random number table.
For example, if the content of the random number broadcast is as follows.
＜123-45-78-90-… … .>
This means the 45th word on page 123 and the 90th word on page 78 of the random number table.
A cipher using a random number table is called a code book cipher. Since the code book method is really simple, if the random number table is exposed, the cipher system is instantly incapacitated.
However, it has the advantage of being very difficult to decipher without a random number table.
For reference, radio communication ciphers are very different from computer communication ciphers.
Since computer communication encryption can be calculated at the same time as it is received, very complex formulas can be used.
A simple example is the RSA cipher.
However, it is not easy to use complex formulas for radio communication encryption such as broadcasting to South Korea, since a person has to decode the command directly.
This means that the number of the CW text contained in the Morse code a while ago is also highly likely to be a random number made from a codebook cipher, not a cipher based on mathematics.
After listening to North Korea’s random number broadcasts to South Korea for the past six months, I was able to figure out some characteristics of codebook ciphers.
In particular, the sentence structure was not difficult to grasp.
It was possible to easily find random numbers that mean the investigation of objective cases such as ‘B’ and ‘B’, which are frequently used, and predict the location of the random number corresponding to the predicate in the sentence using this.
For example, the CW cipher text received this morning consists of a total of 87 numbers, and this cipher text contains one object and one predicate.
In other words, it is a command to do what the object of the object is.
But this password text… I want to decipher this somehow.
I don’t know why I suddenly want to decipher this.
If I just couldn’t decipher this, it seemed like this uncomfortable feeling would continue.
The 87-digit number left in my head started to bother me.
under—! The mathematician is sick again.
Choose the one that bothers you most. (Choose the one that bothers you the most.)
* * *
past life.
I was just starting my PhD.
I handed out a piece of paper outlining the five research topics, and my advisor, Dr. Hamilton opened his mouth without looking at the paper I had prepared.
“(Why did you come to the math department?)”
“(What does that… mean?)”
“(If you had a brain like you, you could easily go to law school or medical school, so why do you want to do math, topology math?)”
Dr. Hamilton’s question gave me serious thought.
Why did I come to the Department of Mathematics?
After thinking for a while, I shook my head and opened my mouth.
“(I don’t know. I don’t know why I want to do math.)”
To my answer, Dr. Hamilton smirked and tapped the paper I prepared for him with his finger.
“(Then, pick the one that bothers you the most here.)”
* * *
“Support—!”
It is the sound of the speaker turning on.
In the end, after work, I couldn’t even sleep. under—-!
With my long sigh, the trumpet began to sound.
“Beeppa- Beeppapa-! Beep-par-bamba–! Beeppapa-!”
Administrative class on the same day.
When the morning interception duty was over, I said to the deputy platoon commander as I finished the work report.
“Deputy commander, I… .”
“why? What’s going on?”
“Perhaps… May I check the full CW records?”
The CW message refers to an encrypted message received as a Morse signal.
At my words, the deputy platoon commander stared at my face.
A moment of silence passed like that, and it seems that one of the soldiers, even a private, said that he wanted to check the cryptography record, and it seems that he had a brain freeze.
I turned my head to confirm that there was only the deputy platoon leader on the administrative team here, lowering my voice and opening my mouth.
“I am Director Kim Jung-soo of the 4th Division of the Anti-aircraft Investigation Bureau of the National Intelligence Service… .”
As the name of Chief Kim Jeong-soo came out of my mouth, the deputy platoon leader, who sat crookedly and looked at me, corrected his posture.
I still spoke in a low voice.
“He told me to ask the deputy platoon commander if there is anything urgent.”
“Yes, yes. right. By the way… What do you want to see?”
“I want to check the CW cipher records, not AM broadcasting (shortwave broadcasting to South Korea).”
“okay? When do you want to see me in?”
“I would like to see the recently recorded material.”
The first thing to do in decryption is to find a pattern in the encrypted numbers.
And, of course, to find a pattern, you need to secure as many cryptographic data as possible.
I spoke to the deputy platoon commander.
“And the more data, the better.”
“okay? So, would it be okay if the data was uploaded to the headquarters in the first quarter of this year? It will be about 200 pages long.”
“Yes, that is enough.”
At my words, the deputy platoon leader got up from his seat and knocked on the door leading to the deputy chief’s office from the administrative team.
When the deputy platoon commander opened the door to the unit commander’s office with the sound of an answer, he saw the company commander and Private Yu Jin-goo talking.
However, the atmosphere between the two is not very serious.
The deputy platoon commander, noticing the heavy atmosphere, closed the door again and said to the company commander.
“sorry. I will be back in a little while.”
Just then, an administrative officer came into the administrative group, and the deputy platoon commander said to me.
“Jeong-ho, I’m on a full-time job today, so come to the administration team right after the roll call in the evening.”
“all right.”
That night.
“what? this bastard! Don’t you know that you don’t have fluid history for 30 minutes after bedtime?”
It was Corporal Park, who was on vigilant duty.
Private Park Kwang-soo, who hated me especially when I was a private, is right.
He was promoted to Corporal three months ago, but he is still anxious because he can’t eat it when he sees only me.
I said to Corporal Park with a calm expression.
“The officer told me to come to the administration team when I start sleeping.”
“okay? Have I not heard of such a thing?”
“Then, please check with the Iljik officer now.”
He looked at me without saying a word and pointed to the administration team.
“Okay, kid! Okay, so let’s go.”
While entering the administrative group, I heard the low-pitched voice of Corporal Park from behind.
“Spicy… get out… . Sheesh!”
After a while, the commander’s room.
The deputy platoon commander said, pointing to the table in the center of the deputy commander’s office.
“We have collected all the data from the third quarter of last year to the first quarter of this year. Let me know if you need more.”
“I think this should be enough.”
“Then I’m glad. But this is quite a bit, doesn’t it take a long time to check it all?”
“It will probably take two or three hours.”
“OMG—! so fast? Yes, anyway, do your best.”
As the deputy platoon leader was about to leave the deputy commander’s office, I said:
“I… Vice-Captain.”
“why?”
“thank you.”
He said with a smirk at my words.
“Thank you… What… .”
So the deputy platoon leader left the deputy commander’s office, and I sat down and opened the file of the report sent to the headquarters in the first quarter of this year.
The report was a compilation of draft CW cipher texts, and was filled with the date and time when the cipher text was received, as well as elongated numbers.
As I turned the paper one by one, I began to put the numbers on the report in my head.
After a while… At the end of page 213, a total of 49,757 numbers in the report for the first quarter of this year have been entered.
I lifted my head to check the time, and the clock was pointing to 23 o’clock.
Still, I’m glad I don’t have a night shift today.
I opened the file of last year’s fourth quarter report.
next day.
The first floor of the barracks.
Incheol said as he sat down next to me.
“Wow–! Jungho, what do you eat so much?”
I said as I swallowed the mumbled rice.
“I’m a little hungry today, haha–!”
“Looking at your table, it’s not that I’m a little hungry, I think I’ve been starving for a few days.”
Corporal Joe also sat in the seat opposite me and helped out with a word.
“Hey–! Jung-ho is eating a lot of gobong rice today. haha–!”
He turned his head to Incheol and continued.
“Incheol-ah, were you okay with the AM broadcast (shortwave broadcast to South Korea) while working at night yesterday?”
“Ugh–! It wasn’t a joke. It seems that the broadcaster’s voice is still ringing in my ears.”
In-cheol continued with the voice and tone of a North Korean male broadcaster.
“Today, April 15th, is the 90th anniversary of the birth of General Kim Il-sung, the spirit of our people and the leader of the nation. On this delightful morning, here in Pyongyang, the capital of the revolution, I would like to hear ＜Long live General Kim Il-sung> to the people of South Korea!”
Then, Incheol started singing with the voice of the marching song’s voice actor.
“Jang-Baeksan stems bloom–Rin Jauk. Ah–the Yalu River bends and blooms-Rin-Jauk. General-nim, on the bouquet of Free Joseon today! A holy mark that illuminates vigorously! Ahh—! I miss that name—-.”
Laughter erupted from all over the dining room.
“Hey–! Do I have to listen to it again in the morning?”
“Choi In-cheol, you crazy bastard! Stop it, man! ha ha ha–!”
“OMG—! I spit it out while eating here in my late years.”
After eating like that, when I got out of the cooking class, the deputy platoon leader, who was standing in the hallway, called me.
“It’s Jeongho.”
“Yes, deputy commander.”
He said, pointing his finger out of the barracks, wondering if he was bothered by the other soldiers around him.
“Let’s go outside and smoke a cigarette.”
As they left the barracks, the deputy platoon commander lit a cigarette and said:
“Is the V19 random number decoding going well?”
“The V19… Could it be the password name of the full text of CW?”
“Yeah, that’s what the Command called it.”
The deputy platoon commander continued, exhaling cigarette smoke into the air.
“But the command said it would be difficult to decipher. The V19 random number table seems to be unsolved by even the American kids.”
Last night, I was able to analyze all the 160,000 numbers I entered in my head, and judging by the ending pattern of the sentences hidden in these numbers, I could see that there were a total of 2734 sentences.
In this way, along with the pattern that signifies the end of the sentence, we were able to find out random numbers corresponding to numbers from 0 to 9.
After decoding the number, it was possible to read a random number representing the unit such as year, month, date, and time, dollar, and won, following the number.
So, the interpretation of the CW text I received at dawn two days ago is as follows.
＜19 XXX, April 15, ZZZ.>
Here, XXX is a noun without a preposition, expected as an object, and ZZZ is a predicate word.
That is, on April 15th, 19 (or 19?) XXX is an order to ZZZ.
At my explanation, the deputy platoon commander said with a surprised expression.
“The command said it would be almost impossible to decipher the V19 random number table, did you find out so much in one night? That’s great.”
“no. I was lucky.”
“By the way, if it’s April 15th, it’s today. Hmm—! This makes me curious too.”
He handed me a note and continued.
“Come on, take this.”
The note had 67 numbers written on it.
“What is this?”
“You know the murder case of Lee Jung-sik three years ago?”
“Are you referring to Kim Jong-il’s nephew who defected?”
The deputy platoon leader silently nodded at my question, and pointed to the note I was holding.
“They said this was the full text of CW that came down two days before Lee Jung-sik’s murder.”
“… !”