##### What is Quantum Cryptography?

We will discover ‘What is Quantum Cryptography?’ in this blog. It is a safe method of communicating when two or more people trade encryption keys. This approach uses the principles of quantum theory to exchange encryption techniques securely and consistently. Maybe because it is sophisticated, quantum cryptography looks to be difficult. We made an effort to make it easier for you.

**Cryptography**

**Cryptography** is the practice of hiding or encoding data so that only the intended recipient can decipher it. For thousands of years, people have been using cryptography to symmetric encryption, and it is still used today in e-commerce, card payments, and password protection.

**Take a quick look at the topics this blog will cover.**

**Table of Content:**

**What is meant by Quantum Cryptography?****QKD’s History****What is the distinction between post-quantum and quantum cryptography?****How does Quantum Cryptography Work?****Difficulties in Quantum Cryptography****Conclusion**

**What is meant by Quantum Cryptography?**

Cryptography is the process of encrypting data or turning plain text into scrambled text that can only be read by a person with the right “key.” By extension, quantum cryptography merely uses the unbreakable encryption and transmission techniques provided by quantum physics.

The intricacy of quantum cryptography, despite the definition’s seeming simplicity, resides in the quantum physics concepts that underlie it. These concepts include:

- The particles that make up the universe are fundamentally ambiguous and can exist simultaneously in different places or states.
- One of two quantum states is randomly chosen for photon generation.
- It is impossible to measure a quantum attribute without altering or disturbing it.
- A particle’s quantum properties can be duplicated, but not the entire particle.
- These ideas all have implications for quantum cryptography.

Two parties can create and share a key with QKD, which can then be used to encrypt and decrypt messages. Instead of the key itself or the communications it enables users to transmit, QKD refers to the distribution technique for the key.

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**QKD’s History**

The idea for quantum cryptography was first put up by Stephen Wiesner of Columbia University in the 1970s with his quantum conjugate coding proposal. In 1983, Wiesner’s paper was published. Based on Wiesner’s research, Charles H. Bennett later developed the idea of secure communication. Additionally, Bennett developed the first nonorthogonal state quantum cryptography technique, BB84. In 1990, Artur Ekert also created a different QKD technique based on quantum entanglement.

**What is the distinction between post-quantum and quantum cryptography?**

- Post-quantum cryptography is the name given to cryptographic algorithms that are believed to be secure from a quantum computer attack. These algorithms are mainly public-key algorithms. In months or even years, conventional computers can solve these challenging mathematical equations. In contrast, mathematically based systems will be quickly broken by quantum computers executing Shor’s algorithm.
- Quantum cryptography, which is entirely unhackable, uses quantum mechanics to convey private messages, in contrast to classical cryptography.

**How does Quantum Cryptography Work?**

- Fiber optic connections are used by QKD to transmit photons, or beams, among entities. When delivered collectively, the various quantum states of the individual photons create a flow of ones and zeros.
- Qubits are the numerical counterpart of bits in this torrent of quantum systems that are made up of zeroes and ones. A diffraction pattern forces a beam to enter a photon collectors by one of two routes once it arrives at its destination.
- The transmitter will then contrast the received data to the emitters, who would have emitted each particle, to determine the order of photons that were sent.
- The erroneous beam collector discards photons, leaving just a particular bit pattern. Then, you may use this bit pattern as a key to encrypt data. The error – correcting method and other comment steps ensure that there are no errors or data leaks.
- Another post-processing step that eliminates whatever knowledge an eavesdropper might have gained about the ultimate private key is postponed security amplification.
- Prepare-and-measure protocols and Entanglement-based protocols are the two main typical kinds of QKD. Detection of unidentified quantum states is the main goal of prepare-and-measure techniques.
- This protocol has the ability to identify eavesdropping attempts and estimate the volume of data that might have been intercepted.
- Protocols based on entanglement deal with quantum states when two items are connected to create a single quantum state.
- According to tangling, evaluating one thing will have an impact on the other. The other partners will be alerted if an unauthorized user takes charge to a formerly trusted device and makes changes.
- The computer is altered by the very act of trying to view photons, making an incursion observable through the use of quantum coherence or quantum quantum states.
- There are two further types of QKD: discrete variable QKD (DV-QKD) and continuous variable QKD (CV-QKD). With DV-QKD, quantum states will be measured using a photon detector and quantum information will be encoded in variables.
- The BB84 protocol is exemplified by the DV-QKD protocol. CV-QKD encrypts quantum entanglement on the phase and amplitude regions of a laser prior to emitting light to a receiver. This approach is used by the Silberhorn protocol.

**Here are some examples of QKD protocols:**

- Decoy state
- BB84
- E91
- Silberhorn
- KMB09

**Difficulties in Quantum Cryptography**

The usage of QKD in the first place, the distance photons can travel, and integrating QKD devices into the existing infrastructure are the three main problems facing the technology.

It is currently challenging to set up the proper infrastructure for QKD. Even though single photon detector problems make QKD insecure in practise, the theory of the technique is entirely secure. Consideration of security analysis is essential.

The fact that QKD depends on an already-existing channel of communication that has been classically authenticated is one of the biggest hurdles. This indicates a sufficient level of security because at least one person has already exchanged a symmetric key. Without using QKD, another cutting-edge encryption method can be employed to protect a system.

**Conclusion**

In order to boost QKD’s overall effective distance and high data rates, new technology is constantly being developed. QKD is being used increasingly frequently in commercial settings as a result of new networks and businesses providing commercial QKD solutions.

Resource : https://intellipaat.com/blog/what-is-quantum-cryptography/