You can participate in the work of deciphering Japanese ciphertext.
Participating in other affairs of the Blue Clothes Society's Secret Service is not allowed.
This is Yu Hua's bottom line.
"We are all people who use our knowledge to help the country."
Hearing Yu Hua's words, a smile appeared on Hua Luogeng's young and tired face, and he responded seriously: "Starting from tomorrow, we will add cryptography courses. We will take a break today. You can study by yourself later."
"Yes, then I will go back to the second bedroom first and teach you to take a rest." Regarding the upcoming work of deciphering Japanese cipher text and the cryptography course, Yu Hua had a look of anticipation on his face, nodded, and reminded the exhausted Hua Luogeng.
.
Hua Luogeng smiled: "Okay."
After finishing this conversation, Yu Hua said goodbye to Hua Luogeng, got up and left the study.
Return to the second bedroom.
"Cryptozoology, deciphering Japanese cipher text, life has become interesting. I don't know what this job is like. I hope I can be qualified." Yu Hua returned to his seat, thinking in his mind, and there was a sense of expectation in his heart.
meaning.
Deciphering Japanese cipher text was a scene that could only be seen in TV dramas in the past. Yu Hua had only seen it in some dramas, but had never had any serious exposure to it.
However, one thing that is common sense is certain, that is, it is completely unrealistic to believe that a single agent and spy can decipher the cipher text in the mythical TV series.
Deciphering codes requires extremely strong logical abstract thinking, mathematical thinking, and systematic knowledge, which ordinary people simply cannot do.
Agents and spies are indeed strong, but their intelligence is not that high.
There is an equal sign between cryptographers and mathematicians.
Yu Hua was somewhat looking forward to this unexpected job. He wanted to do it well and help his master Hua Luogeng decipher the Japanese cipher text.
"There are about 2 hours left for efficient study today. Continue studying." After thinking for a while, Yu Hua shifted his attention and looked at "The Theory of Real Variable Functions" on the desk. There are about two hours left for efficient study today.
Not wanting to waste it, I turned the pages of the book again with my right hand and immersed myself in learning again.
Learning career is like sailing against the current. If you don’t advance, you will retreat.
Nowadays, the time for efficient study per day has increased from 8 hours to 8 hours and 20 minutes, averaging about one minute a day.
There are twenty-four hours in a day, and you can spend the rest of the time fishing and reading calculus to relax your brain and body and mind, but the extremely precious and efficient learning time every day must not be wasted.
Any time you waste a second is a crime.
From a personal point of view, Yu Hua has a lot of time at a young age, and there are still decades to enjoy in the future.
But from a scientist's perspective, Yu Hua's remaining time was extremely scarce and limited.
He is destined to stand at the top of science in the future, has the mission of leading the entire China forward, and cannot afford to waste any time.
Time passes quietly.
Two hours later, accompanied by a familiar dizzy feeling in his head, Yu Hua had to end today's study, quickly interrupt his thinking, empty his brain, and let it rest and relax.
After today's self-study, Yu Hua finally has a preliminary understanding and understanding of the integrability of functions, and is one step closer to perfecting the construction of a thinking finite element analysis system.
After sitting on a chair and resting for a while, Yu Hua stood up, opened the door, and washed up.
The night is already deep.
Winter is about to pass, and spring, which symbolizes hope, is not far away.
"Good night, Yu Hua, tomorrow will be better."
After brushing his teeth, washing his face, and tidying up his personal hygiene, Yu Hua returned to the second bedroom, lay on the bed, looked at the slowly falling snowflakes outside the window, murmured softly, and then closed his eyes.
Tomorrow will definitely be better.
…
The next day.
The sky is slightly bright.
Tsinghua University West Campus, Room No. 28, study room.
"Cryptozoology is the technical science that studies the compilation and decryption of codes. It is divided into two categories. The study of the changing rules of compilation of codes and its application in encrypted communications is called cryptography. Its application in deciphering codes to obtain communication content is called deciphering. Human beings use cryptography.
The history of cryptography is almost as long as writing, or in other words, from the day writing was born, cryptography was born. With the continuous use of cryptography, it eventually evolved into a discipline."
As usual, Hua Luogeng's voice echoed in the study. Today's first class is no longer about the abstruse and obscure calculus, but a brand new mathematics course - cryptography.
Yu Hua sat quietly on the seat and listened carefully.
Hua Luogeng's lecture habit is to start from the beginning, the development history of cryptography, and then talk about the basic components of cryptography, such as cryptographic terminology, keys, plaintext, ciphertext, encryption, decryption, cryptographic algorithms, etc.
The password has confidentiality, authentication, content integrity and non-repudiation,
Confidentiality means that the password sender and the designated recipient can understand the transmitted password content. Authentication means that both the sender and the recipient can determine each other's identity. A third party cannot impersonate the identity of either party. Content integrity is guaranteed to both parties.
Confirm that the content of the transmission password information has not changed during the transmission process. The last point of non-repudiation is that after the receiver obtains the sender's information, it must also verify and confirm that the information indeed comes from the sender. The sender cannot deny itself after sending the information.
Sent message.
An hour later, the basic structure and situation of cryptography had been explained clearly. Seeing Yu Hua's thoughtful look, Hua Luogeng simply asked a few questions. After Yu Hua's answers were flowing, he talked about the development of cryptography in the current era.
"The current development of cryptography is diverse. Germany is the strongest, using a cipher called Enigma, followed by Britain and the Soviet Union, my country and France, the United States last, and Japan should be ranked in the second echelon. I originally heard that Japan Germany has obtained the prototype of the Enigma machine, but I don’t know if it is true. The Japanese encryption system we want to crack now has been confirmed by the Blue Shirts Secret Service as the red secret."
"Hongmi..." Yu Hua chewed this special word carefully.
"Yes, red cipher is upgraded from the green cipher system. I don't know the specific situation, but the red cipher system is composed of language code and replacement code. The language code is Hiroshima dialect, and the replacement code is Hill cipher. It is a symmetrical encryption mechanism
, What we are conducting now is a ciphertext-only attack, and we need to use frequency analysis attack method." Hua Luogeng explained with a serious face.
Ciphertext-only attack is one of the four attack modes in cryptography. It is very difficult. To attack when only the known encrypted text is known, and to try to decipher it, you need to obtain the original plaintext.
Hua Luogeng is naturally indispensable for the original plain text.
Yu Hua nodded thoughtfully.
"Next we will talk about the Hill cipher mechanism and frequency analysis attack method. The Hill cipher is essentially a substitution cipher and uses basic matrix theory principles..."