After the whole family was swept away, I lay down flat

Chapter 685 Code Book

Haijiao originally thought that he knew several ways of writing secret letters and did not need the new method that his younger sister came up with. But after hearing what Haitang said, he became undecided.

Yes, the several secret communication methods commonly used by people today have been used so frequently that they are no longer surprising.

The Wei School in Chang'an has been teaching two basic ways of secret letters for many years: writing letters with rice paste, and writing letters with a kind of ink specially prepared by the Northwest Frontier Army. As long as the matching potion is used, the handwriting of such secret letters can be revealed. Who doesn't know this if they are from Wei School or if someone in their family has attended Wei School? It's not surprising. Nowadays, real military secret intelligence will no longer use these two basic ways of secret letters, because there are too many people who know the decryption method, and it is not safe.

The Jinyiwei in the capital had several other commonly used secret communication methods, but how safe could it be if even the lower-level spies could master them? Not to mention that the nobles in the palace must have their own unique ways to communicate with their confidants outside. In comparison, Haijiao felt that the secret communication methods he knew were really weak.

It would be better to use the method my younger sister came up with. After all, I found the code book myself. As long as outsiders don’t know which book they used to encode, even if they get the secret letter, they won’t be able to decipher the real content.

Haitang also said to him: "Although such a coded letter is a bit too simple, you and I are not important people. The letter is passed between us brothers and sisters. Who would bother to intercept it? Moreover, even if the same word is used in the secret letter we write, it may be a different code. As long as the code book is not leaked, it can be guaranteed to be safe. If you still feel that it is not safe enough, at worst we can write a family letter normally, and then use the rice paste or white vinegar writing method you have learned, and write the code on the blank space of the letter paper. The person who receives the letter must first use potion to make the code visible, copy it down, and find the code book before decoding it. This is double encryption, which is safer."

Haijiao didn't know whether to laugh or cry: "I think...it shouldn't come to this."

Just like what my younger sister said, who would bother to intercept the communication between siblings? There is no need to go through so much trouble for ordinary letters, even if they contain codes. Of course, if it is really confidential, such double encryption can be more secure.

Haijiao thought for a moment and said, "I don't know the situation in Beijing yet, so I can't say which secret letter method will be sufficient. Let's make an agreement in advance. If it's general news, I'll just write it down in the letter home; if it's confidential news that violates taboos, I'll use the method you mentioned; but if it's very important news that absolutely cannot be known to others, I'll make a mark in the letter. When you see the mark, you'll know that I wrote the code with rice milk or white vinegar. You use the potion to reveal the code, then decrypt it, and then tell Xiao Jin the decrypted news... This way it's foolproof."

Haitang thought this was a good idea, using different grading mechanisms for different pieces of news. The brother and sister worked out the symbols for each level, and even explained the potion formula to Haitang in detail, so that the younger sister could buy the ingredients and prepare it at any time.

The brother and sister discussed buying some materials first. After a little practice, Haijiao suddenly thought of the choice of the code book: "What book should I choose? It would be best if it is the Four Books and Five Classics. It can be bought in Chang'an and the capital, but it needs to be produced by a large bookstore."

Haitang thought for a moment, then took out a half-inch thick book from the bookshelf and handed it to his brother: "Brother, what do you think of this book?" Haijiao took it and saw that it was the "Northwest Military Strategy Notes" that he had used in his first year at the University of Science and Technology. The name of this book is quite serious, but in fact it contains battlefield notes written by thirty or forty generals who participated in several important battles experienced by the Northwest Frontier Army in the past few decades, as well as the epic stories that were made up from them. The major universities in Chang'an use it as a supplementary teaching material.

At first, the Duke of Zhenguo took the lead in writing this book because he really wanted to give students of the School of Defense an opportunity to get in touch with the real records of the battlefield and let them learn from the experiences of many famous generals. He and several leading generals also narrated their experiences in a plain, straightforward and real writing style. But the problem is that there are still many generals who may not be good at writing and can only leave it to their literati to do it for them, or they may want to take the opportunity to show off themselves and shape their own wise and brave image. The stories they wrote have many unrealistic colors, such as dreaming of enemy signs before the battle, beheading demons with swords in the battle, one general standing against thousands of troops, and two armies fighting in the dragon gate formation in front of the battle. These plots all came out. It looks like a storybook, and there is not much experience in the battle that can be learned.

It is said that the Duke of Zhenguo really wanted to curse, but the generals could only come up with this version, and the former had no choice but to accept it. The good textbook of Weixue could only be reduced to a supplementary reading material, and most students would throw the book aside after actually taking military strategy classes and knowing what the several major battles written in the book were about, leaving their families to use it as a recreational reading.

But Haitang thought this book was pretty good. The characters were small and printed closely. The whole book had nearly 200,000 characters. Each page had a page number. The whole book used vernacular Chinese. There were many characters and it could be used as a code book. The only drawback was that this book was probably not available in the capital, so Haijiao had to bring it with him to the capital.

But Haijiao would not be suspicious if he brought it with him. He could explain that he wanted to use it to learn military strategies, and he could also use it for daily entertainment to relieve the loneliness of the journey. The book was not thick, so he stuffed it in his luggage without getting in the way.

Haijiao flipped through the book and listened to his little sister talking about its benefits. He had to admit that this was a good choice. At most, he would be laughed at and accused of using a made-up storybook for entertainment, but weren't the excuses ready?
Haitang also said: "Brother, if you feel unsafe, we can find another book as a backup code book. If someone gets suspicious of your book, you can use another code book next time. But it would be best if you don't bring your own, but buy one that can be bought in the capital or Chang'an."

Haijiao thought for a moment and said, "The 'Collected Annotations to the Four Books' published by the Imperial College last year is quite good. It has annotations by several famous teachers of the Imperial College, and many people bought it home to collect. I remember that it is sold in the prefectural school. It is the same edition as the one in Beijing, and the page number is printed on each page. I think... I can use this book as a code book for correspondence between Xiaojin and I. But when I correspond with you, my little sister, I will use 'Notes on the Northwest Military Strategy', so that I don't have to worry about leaks."

When necessary, the two password books can be used alternately. In short, safety and security are the most important.

Haitang had no objection, and immediately took out her purse and prepared to go to the bookstore to buy the "Four Books Annotations" published by the Imperial Academy last year. Haijiao said, "My cousin must have it. We can borrow it first. If it is useful, it won't be too late to buy a new one. Xiaojin also has a copy. I will use his copy to teach him later."

As long as the secret letter is safe and reliable, they don't seem to have to worry about the channel of letter delivery. At worst, they can not go through the path of Ma Shangyi and Lin Shiwei. There are also the Duke of Zhenguo Mansion of the Zhou family, the Marquis of Cheng'en Mansion, and the caravans familiar to the Hai family. Which one can't send the letter to?
Anyway, this is just a letter between the Hai brothers and sisters. If necessary, add a little more money and let the messenger go faster, so there is no need to alarm the people in the palace.

(End of this chapter)