Difference between Quantum Cryptography and Post Quantum Cryptography

What is Cryptography?

Cryptography is the study of secure communication mechanism so that only the sender and intended recipient of a message can read its contents. Microdots and merging are examples of cryptography techniques used to conceal information in photos.

Modern cryptography brings together the subjects of mathematics, computer science, electrical engineering, communication science, and physics. Cryptography plays an important role in e-commerce, chip-based payment cards, digital currencies, computer passwords, and military communications.

The evolution of cryptographic technology in the Information Age has resulted in a slew of legal issues. Because of its potential for espionage and sedition, several countries have categorized cryptography as a weapon, banning or forbidding its use and export. Cryptography is also important in the case of digital media.

In this article, we will discuss in detail about Quantum Cryptography and highlight how it differs from Post-Quantum Cryptography.

What is Quantum Cryptography?

Quantum cryptography is the study of applying the concepts of quantum mechanics to fulfil cryptographic tasks. The prominent application of quantum cryptography is quantum key distribution, which gives an information-theoretically safe solution to the key exchange issue.

At least, in theory, quantum cryptography looks to be a successful turning point in the information security industry. However, no cryptographic approach can ever be totally secure. In practice, quantum cryptography is only conditionally secure, as it is based on a set of key assumptions.

How Does Quantum Cryptography Work?

The sender sends photons via a filter (or polarizer) that assigns them one of four polarizations and bit designations at random: vertical, horizontal, 45 degrees right, or 45 degrees left.

The photons are sent to a receiver, which "reads" the polarization of each photon using two beam splitters (horizontal/vertical and diagonal). The receiver must estimate which beam splitter to utilize for each photon because it does not know which to use.

After the stream of photons has been sent, the receiver informs the sender of which beam splitter was used for each photon in the sequence it was sent, and the sender matches this information to the polarizer sequence used to convey the key. The photons read with the incorrect beam splitter are eliminated, and the resulting bit sequence becomes the key.

What is Post-Quantum Cryptography?

Quantum computers may become a reality. Thus, it's vital to investigate cryptographic techniques that may be used against adversaries who have one. The term used to characterize the research of such approaches is post-quantum cryptography.

Shor's approach for factoring and calculating discrete logarithms on a quantum computer can be used to break a lot of common encryption and signature schemes, necessitating post-quantum cryptography.

While quantum cryptography describes using quantum phenomena at the core of a security strategy, post-quantum cryptography refers to cryptographic algorithms (usually public-key algorithms) that are thought to be secure against an attack by a quantum computer. Post-quantum cryptography is all about preparing for the era of quantum computing by updating existing mathematical-based algorithms and standards.

Quantum Key Distribution

Quantum Cryptography is shown by the Quantum Key Distribution (QKD). It transmits data using photons rather than the traditional approach of utilizing bits. Photons have the property of not being duplicated or modified in any manner, which entities can make use of. As a result, the data transmitted between two parties can be kept private.

QKD employs quantum mechanics concepts to ensure that communication is safe and that no unwanted access is possible. The QKD concept will very certainly be used in highly sensitive information exchange. The communicating entities must be in a certain location. It will mostly be employed in the government, military, and financial services areas, where sensitive information is sent often.

Difference between Quantum Cryptography and Post-Quantum Cryptography

The following table highlights the major differences between Quantum Cryptography and Post-Quantum Cryptography −

Quantum CryptographyPost-Quantum Cryptography
Quantum cryptography, also known as Quantum Encryption or Quantum Security, is a term that explains how the laws of Quantum mechanics can be applied in cryptography.Post-Quantum Cryptography is a set of techniques (typically public-key algorithms) that are expected to be secure against a quantum computer assault.
A quantum channel cannot be properly intercepted without detection, according to quantum mechanics.Algorithms will be studied in order to evaluate their trustworthiness, but there is no assurance that someone will ultimately find a method to break them.
Implementation will necessitate the use of specialized hardware.The majority of implementations will be software-only and will not necessitate the use of specialized hardware.
Only works with optical communications over a free space optical fiber.It works with all types of digital communications mediums, including RF wireless networks and optical communications.
Higher costs due to the need for new hardware and communications infrastructure.Software-based synthesis solutions will be relatively low-cost.
Receiving a Quantum channel, decoding to classical bits, and re-encrypting and broadcasting to another Quantum channel makes a repeater conceivable.Compliant with today's digital repeater technology.
The number of options is really limited. Only line-of-sight nodes should be utilized.Compatible with any form of mobile device communications.
It's possible that it may be utilized for digital signatures, but it's improbable.Different versions of the standards are being developed expressly for the use of digital signatures.


Quantum cryptography explains how the laws of Quantum mechanics can be applied in cryptography, while Post-quantum cryptography refers to a set of algorithms that are assumed to have the capability to secure against an attack by a quantum computer.

Updated on: 22-Jun-2022


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