Introduction to quantum cryptography

The real-world systems of quantum cryptography represent an advancement in the field of communication, wherein the advantages offered by quantum mechanics are used to minimize security threats which are handled with classical computers. This chapter starts with introducing some concepts to the reader about Quantum Cryptography, starting with an overview of classical Cryptography and its limitations in this new era of quantum computing technologies. Certain aspects of quantum mechanics like superposition, quantum entanglement, no-cloning theorem, and their applications for Quantum Key Distribution are also studied. This followed a thorough analysis of key protocols BB84 and E91 to unmask their strengths in securing superior security. Security threats associated with quantum-cryptographic systems and their corresponding provable level of security are considered to strengthen the notion of quantum cryptography as opposed to methods of classical cryptography. The corresponding characteristics of such quantum-cryptographic methods are also discussed for their application in proper targets. By the end of this chapter, we will attempt to explain the conception of some complications regarding quantum mechanics, and how they are now of use in modern practices of quantum cryptography and why such techniques are needed at all.