Shulou(Shulou.com)11/24 Report--

The original title: "do not understand quantum encryption, but also say that you are a communicator?" "

In our online money transfer, online shopping, have you ever thought about whether your information is safe? Are you worried that one day, someone will crack your bank card password and make your money disappear?

Therefore, in order to ensure our information security at all times, all the information encryption algorithms are constantly upgraded.

First of all, let's introduce how traditional communication achieves information encryption:

The traditional communication encryption process is as follows:

Traditional communication encryption process

1. The sender writes the plaintext, and compiles the plaintext into ciphertext through the encryption algorithm and key.

2. The ciphertext is transmitted to the receiver.

3. The receiver translates the ciphertext into plaintext through the decryption algorithm and key.

Thus it can be seen that the "key" is very important in the process of encrypted communication.

Take the RSA key that is currently protecting our "electronic wallet" as an example, if we want to crack the secret key of RSA encryption, we must use very violent methods to decompose a super large number (for example, 1024 digits) into the product of two prime numbers, and it will take decades to crack it with our supercomputer "Light of Taihu Lake".

Do you feel "rest easy" when you see here? Don't take it lightly! The era of quantum computing has begun. Using quantum computers, not to mention the 1024-bit key, it only takes a few seconds to crack the 2048-bit key.

When computing is no longer a problem, information security becomes a problem.

If quantum computers will be the spear to pierce existing encryption systems, how can we protect our wallets and shy little secrets in the future? Can we just let it go?

Of course not! Only magic can defeat magic. Quantum encryption is the "shield" of security that quantum computers cannot break. It is a kind of non-eavesdropping, undecipherable, unconditional and secure communication encryption.

So next, the editor takes everyone to approach it!

01. What is a quantum? In order not to scare everyone away, we can simply understand that the quantum is the smallest inseparable basic unit in physics. For example, the smallest unit of light is the photon, or "light quantum", which is a kind of quantum.

02. What's the difference between quantum encryption and traditional encryption? Just now we mentioned the important role of "key" in traditional communication, and the advantage of quantum encryption lies in its ultimate secret "quantum key"!

Compared with the current ordinary keys, quantum keys are more secure, reliable and undecipherable.

To put it simply, quantum encrypted communication is divided into two steps.

Quantum communication encryption process 1. Quantum key distribution through quantum channel. The quantum satellite sends a pair of quantum keys that are completely random and known only to both sides of the communication. In this step, only the keys are generated and distributed.

2. Ciphertext transmission through the traditional channel. Using the obtained quantum key, the sender encrypts the information into a ciphertext, and the receiver decrypts the ciphertext, thus realizing the complete secrecy of the communication.

03. Is the "quantum key" so reliable? Why? It's really so reliable! Such reliability depends on the randomness and unrepeatability of the quantum.

Randomness in the process of quantum key distribution, quantum satellites randomly send pairs of photons with different polarization states (also known as light quantum, is a kind of quantum).

In order to measure the photon state sent by the quantum satellite, the two sides of the receiver should set up the measurement basis, and for each randomly polarized photon sent, the receiver should randomly place the measurement base to measure.

When the measuring base receives a photon, it is necessary to judge whether the received information is 1 or 0 according to the following conditions.

Photon polarization from Quantum Satellite

The placement state of the measuring base at the receiving end

So, how many states are the photon polarization sent by the satellite?

How many states can the measurement base of the receiver be divided into?

And how to judge whether the received signal is 0 or 1?

There are four polarization states of photons sent by the transmitter: 90 °polarization, 0 °polarization, 45 °polarization and 135 °polarization.

Transmitter-photon polarization state

0 °polarization

90 °polarization

45 °polarization

135 °polarization

There are two states of the measurement base at the receiver: forward and oblique.

Receiving end-measuring base state

Positive position

Oblique release

From the above picture, we can see that:

The photons with 0 °polarization and 90 °polarization can only be recognized by the positive measurement basis, and if the oblique measurement base is encountered, the photon can not be recognized.

The photons polarized at 45 °and 135 °can only be recognized by the oblique measurement basis, and if the positive measurement base is encountered, the photon can not be recognized.

What if it can't be identified? Can only "admit bad luck", and rely on the quantum "magic" property-randomness for random distribution.

For unidentifiable polarized photons, which represents 0 and which represents 1 will be randomly assigned, which is precisely the "strongest killing trick" of quantum keys with super secrecy.

Sending end

Receiving end

Photon polarization state

Measurement base state

(positive)

Measurement base state

(oblique)

0 °polarization

one

0 or 1

90 °polarization

0

0 or 1

Polarization of 45 °

0 or 1

one

Polarization of 135 °

0 or 1

0

To give an example: the satellite sender randomly sends a series of photon pairs with different polarization states, one to An and one to B.

For ease of understanding, it is assumed that the polarization directions of randomly entangled quantum pairs sent by quantum satellites to An and B are as follows:

Photon polarization

Status

(satellite)

The An and B receivers are measured using the following random measurement basis, which can be obtained respectively:

Measuring base

Status

(end A)

0

0 or 1

0

0

one

Measuring base

Status

(B end)

0

one

0

0 or 1

one

Finally, An and B at both ends of the communication use traditional communication methods, such as making a phone call or sending a Wechat, to communicate how the measurement base is placed "straight or sideways".

Then An and B retain the information corresponding to the same measurement base, which we call "quantum keys"!

Therefore, the "quantum key" in the above example is "001", as shown in the following figure.

In the end

Secret key

0

-

0

-

one

In this traditional communication process, there is no need to worry about eavesdropping at all, because even if eavesdropping, we can only get the measurement bases of which are the same and which are different, but this is of no use to the eavesdropper at all. unless he can eavesdrop on the quantum signals sent by quantum satellites to both sides of the communication.

Some people may want to ask, what if there are still powerful people who can eavesdrop on the quantum signals sent by quantum satellites to both sides of the communication?

The answer is "absolutely impossible!" So we have to talk about another important property of quantum.

Non-replicability because the quantum is non-replicable, that is, it cannot be copied or measured without destroying its state, so eavesdropping can be detected immediately.

It is worth noting that when the key is distributed by the quantum satellite, each pair of quantum in the key is in an "entangled" state. If one quantum changes, the state of the other quantum will change accordingly.

In other words, if the eavesdropper wants to intercept the quantum key, then the quantum signal in the quantum channel needs to be measured. According to the "non-replicability", the quantum signal will change the signal itself in the process of measurement.

In turn, it will lead to a great increase in the garbled code of the signal received by both sides of the key receiver, thus exposing the existence of their own eavesdropping, which can be said to be "stealing rice without corrosion".

In addition, each secret key is randomly generated, and once it is bugged, both sides of the communication can detect it immediately and change the password immediately, so it is 100% encrypted.

04. Which one is better than quantum encryption? The editor said proudly: only our country has the world's leading "secret weapon"-Mozi satellite! Mozi quantum science experiment satellite is developed for quantum communication.

At present, quantum communication has begun to move towards practical application.

On September 29, 2017, the "Beijing-Shanghai Line", the world's first quantum secure communication line, was officially opened. the "Beijing-Shanghai Line" has a transmission distance of more than 2000 kilometers, passing through Beijing, Shanghai and other cities, mainly carrying the secure transmission of important information.

After the completion of the "Beijing-Shanghai Trunk Line", it has gone through more than two years of related technical verification and application demonstration as well as a large number of stability tests, safety tests and related standardization research. The results show that the "Beijing-Shanghai trunk line" can resist all known eavesdropping attacks, and the key distribution of the network can support more than 12000 users to use at the same time.

05. When will "quantum encryption" be popularized? Although quantum communication has been put into application in our country, there are still many difficulties in realizing large-scale communication. For example:

There are still distance limitations in quantum channel transmission: the signal consumption caused by long-distance transmission-"the signal is gone when the signal is transmitted."

The number of quantum communication satellites is still very small: China needs to launch more quantum communication satellites in order to form a global quantum communication network.

At present, Chinese scientists continue to make breakthroughs in the field of quantum transmission. Let us have reason to believe that bringing quantum communication into thousands of households is a long way to go, but not out of reach.

This article comes from the official account of Wechat: ZTE documents (ID:ztedoc)

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.