So, this time the Prussians learned to be smart. This simple correspondence cannot completely solve the problem no matter how many times they have done, because they can always trace the origin and find one-to-one correspondence to determine the password. So, they created the adfgv box password. The box of this password is a 5*5 letter matrix, which is used to correspond to 26 English letters. What? You said there are only 25? Then this is easy. Just let i and j correspond to the same letter.

One of the very important reasons why it is called an adfgv password is that the horizontal and vertical coordinates of the 5*5 frame are represented by these 5 letters. According to the letters in the plain text, and then the horizontal and vertical coordinates of the frame are replaced by the horizontal and vertical coordinates of the frame, this is the first step of encryption. In fact, this encryption method is easy to crack. This is the easiest classical encryption method. But unfortunately, this time, the Germans added a key again! The so-called key is another shift encoding. When shifting with a key, use the key character to add an extra column to the original coordinate system, and then write the first encrypted cipher text in the order of 5 lines, and then copy the key in another alphabetical order, thus forming the final cipher text.

The key to the difficulty of deciphering this kind of password is that the key and shift password are changing every day. If you discover it in time, it is useless. Or if you get the initial corresponding form of 5*5, it is not very meaningful. The other party just needs to write a 5*5 form casually. It is possible when cracking, but if you use guessing or simply looking for a one-to-one corresponding method, it is difficult to ensure timeliness and accuracy. What should you do in the era without a computer?

There is only one way, that is, to find the same telegram at the beginning, because this means that they used the same decomposition key and shift key, and then screened through mathematical methods. Of course, there is also an objective condition here, that is, there is enough information to appear repeatedly and enough material to decipher. This is why the Bavarian intelligence team was unable to decipher the other party at the beginning. During the period of accumulating materials!

The whole thing started to turn around in the sixth week. On the 38th day after the game started, the prince handed over the first deciphered telegram to the German Emperor. Two days later, the second letter was sent to Berlin before the end of this week! This means that a total of 120,000 marks had been transferred from the German Emperor's account to the prince's name. When the seventh week came, a total of 18 telegrams were deciphered in just one week! In less than two weeks, the German Emperor lost 500,000 marks!

"Can anyone tell me what's going on? Didn't I ask you to change the comparison table and key? Why is the other party's deciphering speed so fast? We sent the telegram from the morning, and when I had afternoon tea, Bavaria would send the plain text over! I feel that our IQ was insulted, and the other party looked at us with a look of looking at a fool! This is our shame! The empire provided the best conditions for you and the so-called crypto experts under your command with high funds, and see what you did?" The German Emperor said angrily.

"It's now, it's the seventh week. You can't even decipher a telegram. What about Bavaria? They have deciphered 24 telegrams from us! No matter how we change the frame and key, we can't change the result. Then I can only say that your method is a failure. The encryption method you proposed is not trustworthy at all!" At this point, even the German emperor, who has no research on cryptography, knew that he had lost because the other party has adapted to this encryption method, and the space for this password to expand is too small, so no matter how much it is changed, it will never fail.

"Theoretically, there will be enough changes for the corresponding table of 5*5. We can increase the difficulty of deciphering by randomly changing the corresponding method. However, intelligence needs to be transmitted stably, and the corresponding table itself cannot be changed at will. One of our information may eventually be transmitted from the General Staff to a division-level commander. If we want to change the corresponding table without authorization, it will be a very cumbersome process."

"And because of the 5*5 comparison, our shift password can only be 5 digits. The other party can find the breakthrough through enumeration and statistics. If it corresponds to the facts, as long as the key of one of the letters can be found, other information with the same key will be confidential. We admit that the other party's ability to decipher, but I must say that the Kingdom of Bavaria is more talented in encryption. They have developed a new encryption method, which is simply impossible to crack when we read it! Because every phrase is different in every telegram!" Schliffen was convinced. He did not defend his failure, but admitted it clearly!

"That means, we lost again?" The German Emperor's face showed an incredible expression, "But you have said just now that the cipher text of each phrase is different. This means that you have confirmed some phrases, is that true?"

"Yes, the Bavarians are very confident in their cryptographic system. They will even take the initiative to provide us with the correct answers after 3 days, and then we are inverting the cryptographic text according to the given plain text. But unfortunately, the letter correspondence order of each of their cryptographic texts is chaotic, at least we cannot see the rules. When we use the same key, the correspondence of the file is certain. Even if we change the keys every day, we still cannot produce such an effect." Schliffen lost this time and was convinced.

"Okay, okay, okay, we failed again! Look at what kind of people are composed of our General Staff! Finally, I'll give you another week. I hope you can see at least something." Although the German Emperor knew that Schlieffen was helpless when he said these words, he still didn't want to give up.

"I will do my best." Schliffen said in a deep voice.

"Your Highness ****, if nothing unexpected happens, His Majesty William should be unable to withstand it?" At the same time, at Swan Castle, Earl Schelling said to **** with the telegram that he had just deciphered today.

The final result was no surprise beyond the Prussians. They had no choice but to have any help with passwords that had never been repeated, had an extremely confusing correspondence, and could not be interpreted by any existing mathematical method.

"Go to Bavaria and get the new password encryption method! I want to know where we lost!" the German Emperor ordered.
Chapter completed!