1900: A physics genius wandering around Europe

Chapter 600: Superluminal Communication? Quantum Computer! Quantum Encryption System! Unbreakable! The Strongest Code!
Although the principle of quantum entanglement is unknown, this does not prevent scientists from using it to create various high-tech technologies.

It’s like almost no one knows how mobile phones work, but when it comes to using them, everyone is better than the other.

The same is true for quantum entanglement.

Related to it, there are two most well-known technologies that can be regarded as science fiction concepts.

They are: quantum encryption communication and quantum teleportation.

The former gives people the feeling of "superluminal communication", "interstellar communication", etc.

The latter gives people the feeling of "teleportation", "ultra-long-distance transmission", etc.

Unfortunately, these subjective impressions are misunderstandings of these two technologies.

Their essence may be very different from what everyone imagines.

At this moment, facing Wu Youxun's question, Li Qiwei spoke freely:
“I envision two possible technologies that could emerge from quantum entanglement.”

“The first one is quantum encrypted communication.”

Wow!
Everyone was shocked when they heard this!
Professor Bruce is indeed worthy of being a big shot who can run a technology company. He can think of applications at will.

But someone asked in confusion:
"Professor, you just said that quantum entanglement cannot transmit information. How can it be applied to communication?"

Everyone nodded.

This is the shortcoming of quantum entanglement, it cannot transfer energy and information.

Otherwise, it can be directly used for superluminal communication, and the future of the starry sea is not far away.

In later generations, most people think that "quantum communication" is superluminal communication.

As soon as someone publishes a paper saying there has been a breakthrough in quantum communication, marketing accounts become excited.

"Shocking! Using quantum communication, the speed is 10,000 times the speed of light!"

"The Cowherd and the Weaver Girl no longer have to meet on the Magpie Bridge!"

But can quantum communication really exceed the speed of light?

Obviously it is impossible.

Scientists will not even study superluminal communication methods.

Li Qiwei said:
“In quantum encryption communication, the emphasis is on [encryption], not [communication].”

“Before discussing this issue, let me first talk about the classical cryptographic system.”

"When there is war, espionage and secrecy are an invisible underground war."

"If I write directly on paper and it is intercepted by the enemy, the consequences will be disastrous."

"So the spy has to keep the information safe."

"And it is very necessary to encrypt the information."

"The most common encryption method currently is [private key cryptography]."

"What does that mean?"

“Suppose a spy wants to send a message: [Action tomorrow at 5 o’clock].”

"Then he can agree on a conversion rule with his recipient in advance."

“For example, the number 1 represents tomorrow, 2 represents five o’clock, and 3 represents action.”

"The numbers here can also be replaced with text, images, etc."

"This set of information conversion rules that only our personnel know is the key."

"The person receiving the message can translate the original text by simply looking up the key, thus completing an encrypted communication."

"Even if the enemy intercepts the message, they cannot translate the original text because they don't have the key."

“The Morse code that you may be familiar with belongs to the private key cryptosystem.”

"but!"

"This form of password is prone to vulnerabilities and can be cracked."

"For example, if the enemy intercepts information many times, they are likely to use statistical methods to find patterns."

“It’s not a difficult thing mathematically.”

“So, there is still room for improvement in the traditional private key cryptography system.”

"I've read a few math papers before, and one of them was about prime numbers. The author conceived a completely new cryptographic system."

"I was inspired by this paper and designed a completely new cryptographic system."

“I call it [public key cryptography].”

"In the private key cryptographic system just now, only the sender and the receiver know the key."

"Once the key is cracked by the enemy, a new set of keys will need to be designed."

"And public-key cryptography is very different from that."

"First, the recipient designs a private key that is extremely difficult to crack."

"And this key is only known by the recipient, not even the spies on our side."

"Then, based on this private key, a public key is designed."

"Anyone, even an enemy, can send an encrypted message to the recipient by using the public key."

"Once the recipient receives the message, he or she can use the private key he or she knows to translate the original text."

"This method has a significant advantage over private key cryptography, which is that it is not vulnerable to eavesdropping."

"Because the public key is public and known to everyone, while the private key is known to only one person."

Wow!
Everyone was shocked when they heard this!
Professor Bruce actually has such in-depth research in cryptography.

He even created his own set of cryptographic theories.

Simply terrible!
At this time, Dirac suddenly said:

"Professor, the key to this public key system is the private key."

“It has to be absolutely secure and theoretically impossible to crack.”

"Otherwise, your public key cryptography system is actually two private key cryptography systems, with no essential difference."

Li Qiwei smiled slightly.

Dirac was indeed a very intelligent person and he saw the clues at a glance.

"Yes, Dirac is right."

"The recipient's private key is critical."

"And the private key I designed came from that paper on prime numbers."

"We know that mathematically, it is very difficult to decompose a composite number into the product of two prime numbers."

"And as the number of composite digits increases, the difficulty increases exponentially."

“For example, if you are asked to decompose 21, it is very simple: 3×7.”

"But if I ask you to decompose the number 1829375493493834, how would you do it?"

“Not only ordinary people can’t do it, even mathematicians are helpless.”

“That math paper studies this [indecomposability of large numbers].”

"The author found that the time it takes to factorize a composite number increases fourfold for every additional digit."

"Therefore, for large composite numbers that are long enough, human computing power will never be able to crack them."

"It was this property that inspired me to design a public key cryptography system."

“This is how it’s done.”

“Publish the sum of the product of two prime numbers as a public key so that everyone can use it.”

"But consider these two prime numbers as a private key, which only the recipient knows."

"According to the indecomposability of large numbers, even if the enemy knows the composite number, he cannot factorize the correct two prime numbers."

"So, this cryptographic system cannot be cracked."

"Of course, the above is just the basic principle of public key cryptography."

"If you want to design a truly practical password, you have to go through many complicated steps."

"But that's not what I'm concerned about."

hiss!
After hearing this, everyone gasped. Everyone was impressed by Professor Bruce's wisdom.

The public key cryptography system based on the indecomposability of large numbers can simply be described as exquisite!
"My God!"

"Professor Bruce is so scary!"

"He actually thought of using mathematical principles to design a cryptographic system."

“It’s so amazing and so fantastic!”

Dirac nodded admiringly.

He finally understood how the unbreakable thing that Professor Bruce talked about was achieved.

This kind of mathematical calculation is indeed beyond human power.

However, Rutherford, Planck and others frowned slightly.

They had served their country in previous wars.

So they knew very well how attractive Bruce's encryption theory was to the military.

Intelligence confidentiality is always the top priority.

"Bruce won't get into any trouble."

Although Li Qiwei had proposed the hypothesis of nuclear fusion before, there is currently no hope of turning it into a weapon.

But the public key cryptography system is different and has extremely strong feasibility.

It cannot be ruled out that some people are ready to take it for themselves.

Li Qiwei didn't consider this point, he just put forward a principle.

Just like being able to solve Maxwell's equations doesn't mean you can create a wireless telegraph.

Most of the people present were simple physicists, and they were more concerned about another question:
"Professor Bruce has said so much, what is the relationship between cryptographic systems and quantum entanglement?"

At this time, Li Qiwei changed the subject:
"but!"

"The public key cryptography system just now still has a loophole."

"That is: human power may not be able to calculate it, but if we use a machine to calculate it, it may not be the case!"

Wow!
Everyone was shocked!

What kind of machine can handle such a large and complex process?
"Of course, existing abacus and hand-cranked calculators cannot decompose large composite numbers."

“But the world keeps moving forward.”

“Perhaps in a few decades, some kind of [computer] will appear with extremely powerful computing power.”

“As clever as Dirac was, he could only make one calculation per second.”

"But those powerful computers may be able to calculate hundreds of millions of times per second."

"Such a computer has enough computing power to directly brute-force the private key."

Wow!
The whole audience was shocked!

No one could have imagined that just twenty years later, the world's first computer would be born.

Although it was only the simplest and most basic vacuum tube computer, its appearance completely changed human civilization.

Even the most powerful supercomputers of later generations still do not have enough computing power to solve the problem of decomposing large numbers.

For example, if you want to factorize a large composite number with 300 digits, it may take a computer tens of millions of years.

The computer envisioned by Li Qiwei is actually a "quantum computer."

Traditional computers use 0 and 1 to represent the smallest unit of information, the bit.

Quantum computers use quantum bits to represent units of information.

For example, if the spin of an electron is in a superposition state, it can be either up or down, and it can be regarded as a quantum bit.

It is specified that spin-up represents 1 and spin-down represents 0.

In this way, in a traditional computer, one bit can only transmit one piece of information; while in a quantum computer, one bit can transmit two pieces of information.

Therefore, the efficiency of quantum computers is 2^n times that of traditional computers.

If there are 1000 qubits, the computing power of a quantum computer will be 2^1000 times stronger.

This is an extremely scary number!

More than enough to solve the problem of decomposing large numbers!

Of course, even in the future, quantum computers are still in the early stages of research and are still a long way from being put into practice.

But sooner or later, humans will overcome the problem of quantum computers.

Therefore, the public key cryptography system will be eliminated by then.

What Li Qiwei is going to propose next is a cryptographic system based on quantum entanglement.

It is truly "unbreakable".

At this moment, Li Qiwei continued:

“Even if humans develop powerful computers in the future, they can still crack the factorization of large numbers by brute force.”

"But the cryptographic system I am about to propose cannot be cracked by any computer, no matter how powerful it is."

"It eliminates the possibility of being cracked in principle."

"Because it is a quantum encryption system based on the phenomenon of quantum entanglement."

"Using quantum states to encrypt information is called quantum key."

"For example, the polarization direction of a single photon can be vertical or horizontal."

"Let the perpendicular direction represent 1 and the parallel direction represent 0."

"A message is encrypted by a pair of quantum entangled photons."

"Then, once the enemy intercepts this information, he must measure these photons to learn the information contained in them."

"But according to the principle of quantum entanglement, as long as the enemy makes a measurement, it will inevitably change the polarization quantum state of the photon."

"At this point, the receiver and sender will immediately know that the information has been leaked, and they will give up the communication."

“It can be seen that the quantum encryption system is an encryption method that uses physical rules and has nothing to do with the computing power of computers.”

“It’s absolutely secure and cannot be cracked.”

"But the maximum speed of this communication is still the speed of light, and it still has to be transmitted through classical channels."

"The above is my vision for quantum encryption communication technology."

"It has nothing to do with faster-than-light communication, but is concerned with the confidentiality of information."

Wow!
The whole audience was shocked!

Quantum encrypted communications completely stunned everyone.

"My God!"

"In my opinion, public key cryptography is amazing enough, but I didn't expect it could be cracked by brute force."

"Even if it is cracked, Professor Bruce has proposed a quantum encryption theory that cannot be cracked."

“Is this the legendary ‘The higher the virtue, the higher the evil’?”

"However, this Tao is Professor Bruce, and this demon is also Professor Bruce."

"The only one who can defeat that man is himself!"

Everyone was completely conquered by Professor Bruce's wild imagination.

It is actually possible to apply quantum entanglement to cryptographic design.

Quantum encryption systems are impossible to break.

No, it’s not that it cannot be cracked, but our side can instantly know whether the password has been cracked by the enemy.

If not, then continue communicating.

If it is cracked, then interrupt the communication and start again until it is not cracked.

This is simply the most perfect form of password.

"Professor Bruce put an end to cryptography!"

At this moment, everyone had great expectations for the second technology.

(End of this chapter)