Chapter 93 Your method is not suitable
“If a given original text is added with a specific constant to obtain a new plaintext, the cryptographic algorithm can be attacked by comparing and analyzing the plaintext with specific differences and then propagating the changes after encryption.”

"If it were feasible, it might be possible to significantly improve collisions and find different strings with the same hash value in a short period of time."

Xu Yuan is immersed in a state of deep learning at this moment, and his mind is working at an unprecedented speed.

The pen in his hand wrote a large number of equations on the draft paper.

Various thoughts intertwined in my mind.

The collision method that is most suitable for cracking the MD5 password algorithm was born.

I don’t know how much time had passed, but after Xu Yuan finished writing the last mathematical character, he suddenly stood up, stretched out his hands with great excitement and slowly picked up the draft paper on the table.

Looking at the formula above is like admiring a rare treasure.

"really."

“This approach is feasible.”

According to his calculations, the efficiency of cracking MD5 passwords using the above method is greatly improved compared to several other collision methods.

And the reason why he has this confidence, besides believing in himself, is more importantly the change in the progress bar on the panel.

Almost as he stopped writing, he could clearly see that the progress bar, which had dropped to 8%, suddenly soared to 20%.

This means that he has found the correct direction to crack the problem this time.

Simply put, to crack the MD5 password, brute force enumeration or rainbow table collision method is required. As the Bureau of Standards and Technology said, even a supercomputer would not be able to calculate it in a million years.

But his method of attack might be able to shorten the time to a few years or even months.

However, in order to prove that a collision will definitely occur, it is necessary to calculate and list the conditions that satisfy this method.

Although the amount of computing required is also not small, it should be noted that he is not the only one involved in this project.

But the prerequisite is how to convince Professor Wang Xiaoyun and his team to abandon their previous progress and use their own method.

"It seems I have to go to Qilu University in person."

Xu Yuan sat back in his chair, his mind stayed here and he quickly made a decision.

First of all, he now has the confidence to list all the conditions that can be met and use this method to prove that a collision will definitely occur.

However, the time and energy required are too high. If it is really extrapolated over a few years, it will have an impact on his entire plan. Also, Professor Wang Xiaoyun and his team are already very familiar with the ND5 algorithm, and the cracking speed will definitely be very fast if they use a more efficient collision method.

Although it would be difficult for him to convince the entire team alone, he could only give it a try for now.

This is for the benefit of everyone on the project team.

Otherwise, judging by the decreasing progress bar on the panel, continuing along the original path will only get you further away from the destination.

Originally, Xu Yuan planned to take a bus to Yanjing to return to school tomorrow, but plans could not keep up with changes.

Since I happened to find a more efficient collision method, I could only discuss it with Professor Wang Xiaoyun in person.

If you just make a phone call to talk about this, there is no chance of success.

After thinking all this over, Xu Yuan glanced at the time. He decided not to stay up late to calculate the equations. He carefully put away the drafts piled on the table and went straight to bed.

……

The next day.

Xu Yuan made a simple breakfast.

After packing my luggage, I took my uncle’s car to the pick-up point.

Go to the county and take a bus to Quancheng.

Compared to returning to school, the journey to Quancheng is shorter, and we arrived safely after a few hours' drive.

Before coming, Xu Yuan called Professor Wang Xiaoyun. He thought that the other party was still on vacation and had no work, but he didn't expect that the entire project team had already devoted themselves to cracking the password.

This just happened to be convenient for him, as he could complete the replacement of the collision cracking method as soon as possible.

In the afternoon, Xu Yuan stood at the gate of Qilu University.

Although he could go in directly with Qinghua's student ID, he considered that it was his first time here.

I’m worried about going to the wrong place on campus and having others look for me.

It’s better to wait patiently for someone to pick you up.

It was the start of the school term at Qilu University, and there were so many students coming in and out that Xu Yuan was not very noticeable. After about a few minutes, a young man wearing black-framed glasses came over.

Maybe he was still a little afraid to recognize me, so he asked tentatively after he got closer.

"Excuse me, is this Xu Yuan?"

Upon hearing this, Xu Yuan immediately raised his eyes to meet the other person's gaze, and answered with a polite smile on his lips.

"I'm Xu Yuan."

"That's right, Professor Wang asked me to pick you up." The other person's expression suddenly became happy and he said quickly.

Then he took the initiative to help carry Xu Yuan's luggage and walked in front to lead the way.

Faced with such a warm and polite senior, Xu Yuan was used to it and just followed him and found topics to talk about.

After the two parties introduced each other, Xu Yuan learned that the other party's name was Cui Li, a doctoral student.

Currently, I am also working on Professor Wang Xiaoyun's MD5 password cracking project.

As a person specially invited by Professor Wang Xiaoyun to Qinghua University, and also a freshman, the entire project team including Cui Li would naturally be familiar with Xu Yuan.

"Junior."

"I heard that you published a paper in the Annals of Mathematics right after you started college. Such talent is really enviable."

"No wonder Professor Wang personally invited you to participate in cracking the MD5 password." Cui Li said from the bottom of his heart on the way, without hiding the envy revealed in his expression at all.

Thinking about the fact that I am already a postdoc but have not yet published a paper with an impact factor comparable to that of the Annals of Mathematics, while Xu Yuan easily achieved his goal right after entering university, how could I not feel any envy for such a gap?

You should know that when Professor Wang Xiaoyun and several other professors formed a team to crack the MD5 password, he took the initiative to apply and passed the examination before joining.

The fact that Xu Yuan was personally invited by Professor Wang Xiaoyun to participate is very different in value.

"I was also lucky enough to get a glimpse of the brilliance of number theory by standing on the shoulders of my predecessors in mathematics."

"As for Professor Wang inviting me to participate in the project, it was more because he wanted to train cryptography talents for the country."

Xu Yuan listened to Cui Li's words and explained modestly with a smile on his face.

Cui Li just nodded in response, and when he saw that Professor Wang Xiaoyun's office was not far away, he didn't say anything more.

When the two men arrived at the office door and stopped, Cui Li raised his hand and knocked on the door.

The next second, a familiar voice was heard from inside.

"Please come in."

Hearing this, Cui Li turned around and said to Xu Yuan, "Let's go in, junior."

As the office door was pushed open, in addition to Professor Wang Xiaoyun's figure coming into view, there were two men who looked to be in their forties sitting inside.

Judging from the writing board filled with mathematical formulas next to it, they must be discussing some issue.

Wang Xiaoyun stood up quickly when she saw Xu Yuan.

"Xiao Xu is here."

While greeting with a smile, he also introduced them to the other two.

"This is the Xu Yuan I told you about. The new screening method he developed can be used in the field of cryptography."

After that, he turned his gaze back to Xu Yuan and continued, "These two are Professor Wang Changxin and Professor Ding Jian from our department."

"Hello, Professor Wang."

"Hello, Professor Ding."

Upon hearing this, Xu Yuan immediately greeted the two professors.

Wang Changxin and Ding Jian were both professors brought in by Wang Xiaoyun to crack the MD5 cryptographic algorithm.

After Xu Yuan's paper was published in the latest issue of the Annals of Mathematics, they also specifically studied the new sieve method used in it.

It is believed that it can promote the development of cryptography.

That's why Wang Xiaoyun went to Qinghua University to attend a number theory academic conference and invited Xu Yuan to join the team.

It can be said that even without Wang Xiaoyun's introduction, they would definitely not be unfamiliar with Xu Yuan.

"I've heard that a math genius emerged in Qinghua this year, and today I finally saw him in person."

"Stop standing, sit down."

After hearing these words and seeing how enthusiastic the two professors were, Xu Yuan no longer hesitated and sat down on the chair next to him.

"Thank you."

At this time, Wang Xiaoyun also thought of the content of Xu Yuan's phone call, and immediately changed the topic to business.

"I heard you say on the phone that you wanted to discuss the collision method of DM5 with me."

"Professor Wang and Professor Ding are here too. If you have any questions, just ask them and we can discuss it together."

Just as he had said in Qinghua, Wang Xiaoyun did not actually expect Xu Yuan to play any role in cracking the MD5 algorithm.

After all, Xu Yuan had just entered university, and although he had a high talent in mathematics, he had not been exposed to cryptography.

The main purpose of inviting him to join the team and leaving various materials and teaching materials was to cultivate Xu Yuan's interest in cryptography, and to enable him to achieve results in the field of cryptography in the future with his talent.

To sum it up in one simple sentence, it is to train cryptography talents for the country in advance.

However, there is no way around it. After all, there is still a blank in the field of hash function cryptography in China.

In addition to requiring a large number of outstanding relevant talents, it is also necessary to design your own absolutely secure hash function password.

After all, this is related to information security and is of great strategic significance.

"Hash functions are more complex than many mathematical topics. It's amazing that you can teach yourself hash functions. It's no wonder that you can solve the Carmichael number spacing problem in number theory with this talent."

Before Xu Yuan could answer, Professor Wang Changxin next to him couldn't help but take over the conversation and said something.

The words were full of affirmation and praise for Xu Yuan.

Hearing this, Ding Jian encouraged: "If you have any questions, just ask directly. Don't be restrained."

"Just think of us as your math teachers. Only by talking to us can we find a solution."

In their opinion, Xu Yuan came to Qilu University at the beginning of the school term because he must have encountered difficulties in his research on hash functions and wanted to ask for advice.

Since the purpose is to train talents for the country, there will naturally be no differential treatment among different schools, not to mention that Xu Yuan is a member of the project team.

As for Cui Li, who was standing at the back, he also pricked up his ears, wanting to hear what problem Xu Yuan had encountered. You know, the opportunity for three professors to give a lecture together is rare, even in school.

Having said this, Xu Yuan didn't want to delay any further, and the next second he stated the purpose of his visit.

"I told those professors that I think the collision method you are using to crack MD5 passwords is not suitable."

……

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(End of this chapter)