Quantum Key Distribution: The Evolution

Quantum Key Distribution: The Evolution

Bhavesh B. Prajapati (IT Department, Commissionerate of Technical Education, Government of Gujarat, India & Gujarat Technological University, India) and Nirbhay Kumar Chaubey (Gujarat Technological University, India)
Copyright: © 2020 |Pages: 15
DOI: 10.4018/978-1-7998-2253-0.ch002


Quantum key distribution is an application of quantum cryptography which is based on quantum mechanics and optical physics. The word “quantum” means the smallest particle of matter and energy which inhibits unique special properties to make it different from normal matter. This chapter discusses underlying principles, and operations of quantum mechanics which are used to derive quantum key distribution protocols. This chapter also discusses elementary QKD protocols based on no cloning theorem and EPR correlations. Limitation of quantum key distribution is also discussed with reference to its implementation. Conceptual notes on quantum internet are also given.
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Today’s world is flooded by exponentially increasing small mobile devices having enormous computing power and giant central servers. The need of communicating secret messages among parties is basic demand and hence need to be attained by cryptographic solutions. Cryptographic solutions should not only be used for solving current needs but it should also address the assumptions of increasing computational power in future with reference to technological advancement.

Current classical cryptographic techniques solely depend on complexity of mathematical algorithms and limitation of current computational power to break it with reference to time constraints. Application of basic principles of quantum physics for cryptographic solutions proves almost all classical cryptographic solutions are inadequate for use and promises to provide unconditional security in quantum key distribution which is unattainable task using classical techniques.

Quantum technology is an emerging field now a days and current quantum devices are capable enough to break the latest classical cryptographic solutions in fraction of time. Quantum factoring algorithm developed by Shor can break RSA scheme easily. New emerging field Post Quantum Cryptography aims to develop cryptographic algorithms which are future safe against quantum computers. Such technological developments point out towards the need of more challenging and complex protocols for security.

How It Started

At MIT in 1981, Richard Faynman coined the idea of Quantum Computer and proposed a conceptual model of quantum Computer. He assumed that quantum computer will replace classical computers in near future but the first break through was achieved almost after 10 years when in 1994, Peter Shor proposed Shor’s algorithm. Shor’s algorithm can efficiently factorize large integer exponentially faster compared to classical computers. To factor large numbers like a 300 digit number, classical computer may take millions of years but the same can be done by the quantum computer in few minutes. Quantum computers and related research are gaining attention of many due to the ability of breaking cryptosystems in negligible time.

In 1996, Lov Grover presented a database search algorithm based on quantum techniques which solves the problem of random search or brute force search four times faster than search techniques using classical computers. First functioning 2-qubit quantum computer was built in 1998 which was capable to solve Grover’s algorithm. This development started a new era of technical advancement in quantum computing and its applications. Recently in 2017, IBM built a commercial quantum computer and raised the bar to new level.

Quantum Information and Quantum Processing

A quantum computer is a device which is based on the underlying principles of quantum mechanics. The basic unit of operation which is used for quantum computer is quite different in structure and characteristics than in classical computer. This unit of operation is called a “Qubit.” When quantum computer is being operated with classical data gives normal efficiency but key to outperform classical computer is the use of qubit because of its properties which are discussed in later sections.

Quantum computers differ with classical computers in following points:

  • Quantum operations are exponentially faster than classical operations and hence result in great efficiency.

  • Inhibit properties of a qubit allows its use in multiple ways which is not the case with classical bits.

  • One cannot measure the position of qubit due to its super position state. If one tries to measure its position, it collapses to either of the states and this feature is essential in achieving privacy.

  • No-Cloning property of qubit ensures that quantum information is impossible to be copied.

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