A Detailed Guide on Quantum Cryptography with Pros and Cons

Quantum cryptography is the next level of encryption used today. Originating from principles of physics, this segment of encryption involves the mechanisms of physics mixed with computing power. This computing power and quantum mechanisms are used to create two powerful security systems, quantum key distribution, and quantum-safe cryptography.

We will take you through the details of quantum encryption and cryptography in this guide. Going forward, you will also learn about how quantum cryptography works and what its applications are in our world.

Explaining Quantum Cryptography

Quantum Cryptography applies the tenets of quantum mechanics to encryption and cryptography. With the mechanisms of quantum integrated into encryption, the resultant security is so tightened that no one can access the data being shared and secured with this system.

Even if a hacker would have access to quantum computers and the entire kit, they cannot crack the encryption provided here. This is because quantum encryption leverages quantum’s multiple states and the “no change theory” to secure the information.

There is no doubt that quantum encryption is better, more reliable, and more authentic than the traditional cryptographic measures we are using till today. The highly popular Advanced Encryption Standard (AES) makes the data virtually unhackable, but it does not make anything impossible to hack.

Alice and Bob Demonstration

To depict the working behind quantum encryption, we were given a case example that will help make things more clear. So, take that Alice wants to send a message to Bob. As she writes the message and runs it through the polarizer to polarize every single photon to change its orientation into a particular type. This can be horizontal, vertical, or diagonal.

The encryption key here is the change in the orientation of the photons. Upon receiving, Bob would guess the polarizer and decode the message. Here Bob would guess and match the photon cases with the ones Alice has generated.

In this case, suppose there is another person who is trying to access the message. In the crypto world, this person is called Eve. Eve is using its own polarizer for accessing the message. In case Eve uses the polarizer for decoding purposes, Bob and Alice would say that there are discrepancies because we cannot change the property of a photon without moving or changing it.

With this principle at the backend, quantum cryptography was developed and used as a protective measure to secure data, transactions, communication, and information.

Principles Behind Quantum Cryptography

Quantum cryptography leverages individual particles of light like photons for data transmission and transfer. This data is transmitted over fiber optic wires. The photons represent binary bits, hence the security depends on the execution of quantum mechanics.

The utilization of photons or light particles is effective because these particles can exist in two or more places simultaneously. Also, any quantum property cannot be changed or observed without first changing it, and the particles cannot be copied.

With these aspects, quantum cryptography is able to provide the highest form of security. Some might say that the keys shared via quantum cryptography are unhackable because of the principles of photons applied here.

However, we are seeing some possibilities of getting around the security provided by this system. But nothing has been proved or demonstrated as of yet and even with quantum computing power, hacking a quantum key is not easy.

Let’s get into some detail about photons. Every photon passed through the encryption system in quantum cryptography represents a binary code number. It can be either 0 or 1.

The key represents a string of 1’s and 0’s creating a coherent message that only the two entities involved can use for encryption and decryption. The way quantum computing encryption works is similar to the AES, but due to the properties of photons, we can see a big change in security.

The binary bits converted from the photons provide a distinct spin to the photons. It can be vertical (|), horizontal (-), diagonal to the right (/), or diagonal to the left (\). This provides a unique code or cryptographic property to the key.

Heisenberg’s Uncertainty Principle

This principle states that we cannot measure or calculate the position and momentum of an object. This principle does not apply to the macroscopic world because minute changes in that world are often ignored.

But in a quantum world, even the slightest change can make a big difference. Hence, the Heisenberg Uncertainty Principle has a big role to play in quantum computing and cryptography.

Why is there a Need for Quantum Cryptography?

Have you heard of the phrase, “Necessity is the mother of invention”? Well, the inception of quantum encryption and cryptography has a similar story. With the coming of quantum computing, the existing encryption standards may have become vulnerable.

Using Shor’s algorithm in quantum computing, computers have broken the asymmetric encryption. Normal computers cannot find the prime number that is the key to finding the decryption key in the RSA encryption standard. But a quantum computer can find the prime number. Hence it can break the key.

For the AES, the AES-64 bit and AES-128 bit have become vulnerable with the brute force attack from a quantum computer. While they are still not hacked, the brute force attack has reduced the security net.

This is to the extent that the AES-128 bit is reduced to AES-64 bit, and the AES-256 bit is reduced to AES-128 bit. The AES 128-bit standard is still strong enough to protect the information, but we can say that it is only a matter of time before quantum computers can crack the code.

Quantum-Safe Cryptography and Quantum Key Distribution (QKD)

Two concepts come out of quantum encryption and cryptography;

Quantum-Safe Cryptography

Quantum-Safe cryptography identifies the methods, efforts, and algorithms that will make a key resistant to attacks. It basically identifies the measures that will make any piece of data secure from hacking attacks from a classical computer we use in daily life or a quantum computer.

The focus here is on quantum computers because they have higher computing power and possibilities.

Quantum-Safe cryptography is also called Post-Quantum cryptography. At present, NIST is working to solicit, evaluate, and standardize quantum-resistant public key cryptographic algorithms. Once they are approved and standardized, quantum cryptographic keys will become available for public use.

The existing encryption standards like AES, ECC, RSA, etc., use mathematical equations to generate cipher text. But with quantum cryptography, we can generate cipher text with physics and mathematical equations, both.

Quantum Key Distribution

Quantum Key Distribution (QKD) involves sending data in the form of photons across an optical link. The motive here is to ensure the protection and security of the data, and QKD provides it easily because of the systems generated with quantum cryptography.

The higher form of security provided by QKD stems from the fact that it can easily detect any sort of intrusion. This will alert the interested parties or entities, and the key used for data transmission can be discarded.

QKD is most commonly used in communications channels. We can select from a number of protocols to implement QKD. But it requires a quantum channel and an authenticated classical channel.

The quantum channel sends the state of light in the form of photons and the classical channel is for the sender and the recipient.

Is Quantum Safe Cryptography “Unhackable”?

In every discussion about quantum encryption and cryptography, the laws of quantum mechanics will always pop up. The activity where encryption keys are sent in the form of photons to and fro between two entities is theoretically untraceable.

The fiber optic lines are the key element in this system. We have discussed all the fiber optic lines and how they make transmissions secure. However, there is another way of transmission used here, where satellites are used to exchange the keys.

In the satellite-based approach, the principle of Entanglement comes into play. China has been using this technology for sending and receiving quantum-safe cryptography data and messages.

Digressing a little from the topic here, in entanglement, two particles are entangled to a level that they achieve the same state. Once this is achieved, one of the particles is sent to someone else. After the particle is received at the other end, it is ensured to have a similar state as its twin.

In case, one of the particles changes, the other particle will change to match is not an assured fact. This is because we are not using the entanglement for communication purposes.

So, we cannot use this property for communication, but it can be used to share encryption keys, which then can be used for securing communication over traditional channels.

Based on the equipment, technology, and systems applicable in this system, we can say that, at present, quantum cryptography is unhackable. Yes, even with the quantum computing systems we have access to today, hacking communication, data, and transmission is not virtually possible.

Benefits and Disadvantages of Quantum Cryptography

Given its advantages, quantum encryption and cryptography also have a few disadvantages. Let’s go through the benefits first.

Benefits of Quantum Encryption

• Communication is Secured: With quantum cryptography, the communication is secured to a higher level than a traditional encryption standard. Since it's based on the laws of quantum physics, communication is more secure.

• Multiple Security Methods: Quantum computing and physics help provide the required security via different methods. We have discussed entanglement and polarizer in the sections above. But more methods can be derived in the future with more research and development.

• Detecting Eavesdropping: With quantum-safe cryptography, we can detect if any party other than the two entities authorized to access the data is trying to trespass.

  
  

Limitations of Quantum Cryptography

Even a technology as good as quantum cryptography has its limitations.

1. Limited by Range: Since the entanglement system has limited applications, we have to rely on fiber optical cables to implement quantum encryption. And these wires can only be laid for a limited distance. The longest we have is up to 500 KMs.

2. Polarization Changes: Photons are susceptible to changing their polarization, even when they are in transit. This can lead to higher error rates.

3. Costly Equipment: Not just the fiber optic cables, but all kind of equipment required to setup and install a quantum cryptography system is highly expensive.

   
   

Conclusion

From mathematical equations helping us secure our data and online communication to using physics for the same purpose, we have evolved. With quantum computing and cryptography allowing businesses, governments, and organizations to secure their data further, it is going to become virtually impossible for hackers to hack into systems and eavesdrop into conversations.

Even with its limitations, quantum encryption and cryptography are highly secure and useful. Once approved for public use, we can expect its limitations, especially about the higher costs going down once it gets more traction.

In the time to come, we can see a large-scale implementation of cryptographic technology.