Quantum Cryptography Basics

Unlike conventional cryptography systems, quantum cryptography is not based on mathematics. It is based on physics, and it is extremely secure. The quantum property of light or photon is incorporated in quantum cryptography, and this makes it unbreakable, since it is not possible to measure the quantum state of the photons. As such, any message that is sent or received cannot be modified or compromised without the permission of the receiver or the sender.

* Introduction to Quantum Cryptography: Basic information on quantum cryptography.
* Quantum Cryptography Explained: Detailed explanation of the quantum cryptography concept.

Standard Cryptography

In standard cryptography, a set of keys is used to encrypt a message. Before sending the messages, these keys will be encrypted. There are fundamentally two types of standard cryptography, namely, the traditional system and the modern system. In the traditional system, reordering of characters, substitution of plain-text characters, and use of alternative words are some of the methods that are used for encrypting messages. On the other hand, modern cryptography uses very long keys or complex algorithms to encrypt messages. The downside of standard cryptography is that it is not completely secure, and it can be compromised.

* Modern Cryptography: An overview of modern cryptography.

History of Quantum Cryptography

The precursor to quantum cryptography was conjugate coding, which was invented in 1969. In 1984, a paper by Gilles Brassard and Charles Bennett described the system of quantum key distribution. Doug Wiedemann was another scientist who contributed greatly to the development of quantum cryptography in the 1980s. The study of quantum cryptography was revitalized in the 1990s, with Arthur K. Eckert's International Cryptography Workshop paving the way for rapid development in the field of quantum cryptography. Since then, there have been numerous quantum cryptography conferences. Today, quantum cryptography is one of the most widely discussed topics among scientists and computer engineers.

* Quantum Cryptography History and Basics: Account of the history of quantum cryptography, and explanation of its basic concepts.

Quantum Coding

Modern cryptography uses bits to create complex algorithms. Quantum cryptography, on the other hand, uses quantum states known as “Qubits” to encode messages. Photons are used because it is comparatively easier to send photons through digital communication networks such as fiber-optic cables. The most important feature of “Qubits” is that the quantum state will change whenever someone attempts to measure it. As such, if anyone tries to eavesdrop on a message that is quantum coded, the sender and the intended recipient will invariably come to know about it.

An Example Protocol

The BB84 system is a cryptographic protocol that was developed by Brassard and Bennett. In this system, a person sends an encrypted message and another person decrypts it, with both of them using a polarizer. For example, Jill sends a message through a polarizer, which can polarize a photon in four directions. Now, Jack doesn’t know which direction each of the photons is polarized in. So, Jack and Jill use a public platform to have a discussion after all the photons that contained the message have been sent. Jill doesn’t tell Jack the actual measurements; she only says which of the measurements were correct or incorrect. In this way, any eavesdropper on the public network will be unable to understand or decipher the transmitted message. Finally, by eliminating the incorrect measurements, Jack will be able to decrypt the message.

* Quantum Cryptographic Protocols: Comprehensive explanation of how quantum cryptography works.

Quantum Privacy Attacks

Although it is believed that quantum cryptography is impregnable, there are certain quantum privacy attacks that can jeopardize communication between the sender and the receiver. One of the known privacy attacks is the “Man in the Middle Attack” or “Bucket Brigade Attack”. An eavesdropper can intercept the message by the sender and respond to both the sender and receiver, thereby, fooling both of them. In this way, the eavesdropper can retrieve the secret key in its entirety.

* The Security of Quantum Cryptography: Article that discusses the potential weakness of quantum cryptography.
* Defeating Man in the Middle Attack: Find out how to defeat Man in the Middle Attack in the distribution of quantum key.

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