Do you know what quantum cryptography is and what changes it will bring in the future? He **Development of quantum computing will bring significant changes to the calculation speed of computers**. Processes that could take millions of years with current technology would be reduced to viable times thanks to this type of computing. In cryptography, it is evident that the development of this new technology will bring an impact and, in fact, this was mathematically proven more than two decades ago.

In this post, we will explain **what is quantum cryptography**what properties it is based on and what post-quantum cryptography is about.

## What is quantum cryptography?

Quantum cryptography is a branch of mathematics that applies the theory of the development of quantum computers to **two main functions**which, in the future, will be developed in practice.

The first function of quantum cryptography is to **break existing cryptosystems**, such as the RSA asymmetric encryption algorithm, the Diffie-Hellman key exchange algorithm or the AES block encryption algorithm, among others. These are currently used and are considered safe when implemented properly. When broken, HTTPS communications would be possible to decrypt. The second function of quantum cryptography is to **develop new cryptosystems with quantum computers**. The importance of this type of computer lies not only in its ability to break systems, but also in creating more efficient ones, thanks to its immense computing capacity.

*Properties of quantum physics*

*Properties of quantum physics*

To understand what quantum cryptography is and what it could look like in the future, it is worth doing a brief review of the laws of quantum physics that will enable this type of technology. Mainly, the development of a quantum computer is based on the following properties of quantum mechanics:

**The quantum superposition**: is a property of light particles (electrons and photons), which allows them to be in several quantum states at the same time. Therefore, its representation is done through the sum of said states.**Quantum entanglement**: It is a property that implies that two or more quantum particles are united in information despite how separated they are. This allows us to know the quantum state of the other particle at a speed faster than that of light.**Change with observation**: In quantum physics, this means that it is impossible to measure the state of these particles without modifying them. In fact, its state does not manifest itself until an observer measures it.**Use of qubits**: The qubit (in English «qbit») is the unit of measurement for quantum information processing, which is planned to be used in medium-term future computers. Qubits continually change value, but they are directly related to other quantum particles that change at the same rate and at a speed greater than that of light.

## Post-quantum cryptography

Now that we have seen what quantum cryptography is and what principles it is based on, we will talk about **post-quantum cryptography and how it differs from the previous one**.

Post-quantum cryptography, unlike quantum cryptography, is responsible for developing algorithms resistant to attacks with quantum computers. Currently, it is expected that many of the cryptosystems and protocols that we use every day can be decrypted through quantum computing. Nevertheless, **Ways to improve current algorithms and develop new ones are also studied.**. The encryption algorithms most vulnerable to quantum cryptography are:

RSA: one of the** asymmetric key algorithms** most used in binary computing. Key exchange with Diffie-Hellman: used to **exchange private keys during the handshake** in security protocols such as HTTPS.AES: the Advanced Encryption Standard is the

**block cipher algorithm**which is used as a standard in all communications. It will be vulnerable to attacks with quantum computers, but analysts have found that using keys twice as long will be enough to restore its security level.

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