Since he couldn't hack the servers of major platforms during the investigation, Yan An chose the most common way - number theft.

The email account in front of him was deeply hidden by Wu Juren, and it has nothing to do with the information that can be found on the surface, if it weren't for BT's network monitoring of several IP addresses he commonly uses, I'm afraid he would really ignore this mailbox.

After discovering it, Yan An easily logged in to this mailbox.

It's also funny, the mailbox is tightly hidden, and it has almost nothing to do with Wu Juren, but the password is commonly used by him, and Yan An only tried twice to get it.

After logging in, Yan An was refreshed by the discovery that this email address had only been linked to one account, dating back to the period when Wu Juren went abroad decades ago.

The account creation address is in the Yellow Widow Kingdom, and the mail server of the Yellow Widow Kingdom is also used, and it is difficult to register such an account in Zhu Chi.

Other than that, there is no body communication for each email, only file transfer, and it is very stable, basically only two emails per month.

A little more peculiarly, it was seven years ago, when there was a lot of communication, and there was an almost daily exchange of emails.

Yan An tried to download the file, but thankfully it wasn't a hassle since the mail server still had it saved.

It's just that the downloaded files can't be opened and read directly, all the files are encrypted, and what you get when you open Yan An directly is a bunch of garbled characters.

"Where is the email address and IP address that contacted him?" The content of the document will not be able to be solved for a while, so Yan An has to start from the other side.

It is much faster to investigate if there is a target, although Wu Juren hid this mailbox tightly, but the other party who communicated with him was not difficult to check, and soon BT gave the answer.

"According to the investigation data, this address is the office building of the Ministry of Foreign Affairs of the Yellow Nation."

"The Ministry of Foreign Affairs of the Yellow Widow Kingdom?" Yan An was confused for a while, he was not familiar with the various organizations in the Blue Dome Star International, and he didn't know much about the Huang Wei Kingdom, and when he heard this, he thought that it referred to the name of a certain place like Zhu Chi.

Finally, after checking it with his mobile phone, he learned that it was the highest organ of foreign relations affairs of the Huang Wei Kingdom, similar to Zhu Chi's Ministry of Foreign Affairs.

Then it shouldn't be in contact with friends, Yan An judged, after all, all communication takes place during working hours, and I don't think that anyone's friends only exist when they are fishing at work, and they disappear without a trace after work.

"Are there any other connections between them? For example, in the case of money exchanges, the scope of the investigation should not be limited to Wu Juren, but also include the people around him. ”

“…… Searching, search complete. Twenty-three people who had been in contact with Wu Juren within a year had similar email addresses, including seven with unknown sources of money.

One of these seven people is an apprentice of Wu Juren, whose name is Lu Wenren, and he will receive a transfer every month, which will be transferred to Wu Juren's account on the same day, and the transfer will be remarked as an apprenticeship fee. ”

This information simply does not stand up to scrutiny, and compared to the hidden mailbox, BT does not need to hack into the banking system of Huang Weiguo to obtain these fund flow records.

Seeing these news, even Yan An could determine that something was wrong, and he didn't know how Wu Juren, who was the designated partner of the Monkey Sect Society, avoided censorship.

Maybe no one has checked it at all, or maybe someone wants to check it but is blocked back.

In short, the things involved in this are too complicated, and there is no more information in terms of email, Yan An can only look at the files he downloaded, "BT, can you analyze what type of encryption method he uses?" ”

The cryptography of the Dome dates back to before the Common Era, and with the advancement of technology and the needs of warfare, this technology has been further developed.

From the most classic displacement encryption to the current RSA asymmetric encryption algorithm, there are thousands of different encryption methods.

If you can't determine which encryption method is used for the ciphertext, it will be difficult to crack the encrypted information by exhaustive method even if BT is running at full power.

Yan An is not familiar with this aspect, so he can only hope that BT can count the feature rules in the ciphertext, so as to judge the encryption method used.

As long as the encryption method is determined, decryption is relatively much simpler, after all, in this regard, Mingxing is definitely stronger than Biqiongxing.

The civilization on the Ming Star is even more complicated than the civilization on the Blue Dome before it leaves the home planet.

At that time, there were seven or eight super government organizations on Mingxing, and it was in the Cold War for a long time, which promoted the rapid development of Mingxing technology at that stage, and various encryption methods emerged in an endless stream, and even children on the border at that time had to use code words for conversation.

Up to now, although Mingxing's demand for encryption methods is not so high, resulting in a slower development of cryptography, it still maintains a posture of keeping pace with the times, and compared with Biqiongxing's cryptography, it still has thousands of years of technological leadership.

This time, BT was much slower to respond, and it took a while before giving an answer.

"The preliminary judgment is that it is the Blue Dome RSA encryption algorithm."

Just as Yan An was still using his mobile phone to search for what the RSA encryption algorithm was, BT followed up and said, "I'm sorry, Your Excellency Captain."

I couldn't find the private key in Wu Juren's possession, and according to the analysis of the data of the idiomatic computer, the private key should be on a device without an Internet connection. ”

The RSA encryption algorithm encrypts the plaintext through the public key, and after the ciphertext is sent, the receiver still holds the private key corresponding to the public key, and only the private key can be used to decrypt the ciphertext, and the security factor is relatively high.

Wu Juren and the Ministry of Foreign Affairs of Huang Wei did not unilaterally send ciphertext out, and he would also get ciphertext replies every month, so he must have a set of public keys and a set of private keys in his hands, and if he is lucky, this public key and private key will be corresponding.

If you can get the private key from Wu Juren, you can easily decrypt these ciphertexts.

It's a pity that he is very cautious in this regard, decrypting the private key in a device that is not connected to the Internet, and no matter how powerful Rao is BT is, it is impossible to complete the invasion.

"What about the public key? If you have a public key, you should be able to derive the private key as well, right? ”

Since the RSA encryption algorithm has been developed in Biqiongxing for nearly 40 years from its proposal to the present, as the security of this algorithm has been affirmed and widely popularized, more and more people have participated in the research of this encryption algorithm, and Yan An can easily find the simple science of this algorithm with his mobile phone.

The algorithm itself is based on a simple number theory knowledge, given that it is easy to multiply two prime numbers, but it is difficult to reverse the two prime numbers for the product result, as long as the fast method of solving the large integer factorization can be solved, this encryption method will be easily cracked.

In order to make RSA encryption more secure, it is common to choose two very large prime numbers to be multiplied, and these two prime numbers will exceed 1024 bits after being converted into binary, and the more digits the more difficult it is to crack.

The product of these two primes can be known through the public key, and as long as these two primes can be decomposed, other problems will be solved.

Of course, the premise is that the public key can be known, and all the possibilities of cracking are based on the known public key, and if you don't even know the public key, the difficulty of decryption will increase exponentially.

Yan An's sharp mind quickly discovered the key, and luckily BT found out the encrypted public key used by Wu Juren.

As the name suggests, this thing is public, and no one has been able to calculate the private key from the public key, so Wu Juren is not so cautious.

Having a public key is not the end, although this thing can encrypt plaintext, but RSA is an asymmetric encryption algorithm, and the ciphertext can only be decrypted by the private key in most cases, and the public key decryption is usually applied to digital signatures to verify that the data has not been tampered with.

Obviously, the documents sent by Wu Juren and Huang Wei's Ministry of Foreign Affairs were not digital signatures, and he had to crack the private key to know the contents of these documents.

This task is currently not possible for BT, after all, Mingxing does not use RSA encryption algorithm, no matter how complicated BT's functions are, it is impossible to include this one.

However, if he can write an algorithm to successfully complete the factorization of large integers, and then complete the cracking of the RSA algorithm, then he can add such a function to BT.

"I need knowledge of factor factorization of large integers, which should be in number theory, starting with simple basics."

"Recommending to you." After a while, virtual bookshelves were projected on the screen, arranged from basic to advanced knowledge, with more than a dozen books, each of which looked thicker than a brick.

In the face of these books, Rao is Yan An couldn't help but have a headache, I am afraid that he will not have to do anything else in the next half month, and these books alone can fill his itinerary.

However, the process of acquiring knowledge is quite enjoyable.

Taking advantage of the fact that there were still a few hours before it was time to go to bed, Yan An happily began to study the basics of number theory.