chapter  8
Quantum cryptography
Pages 44

The word cryptography originates from two Greek words: kryptos (secret) and graphein (writing). Thus cryptography is the art of communicating a message in secret manner or in other words, it is the art of rendering a message unintelligible to any unauthorized party. Its history is very old and exciting. From the beginning of human civilization there was a need to hide information from unauthorized people. This need gave birth to cryptography. Initial cryptographic protocols were very simple. With time they have become much more sophisticated and secure. However, all the classical cryptographic protocols developed so far are secure under some assumptions. In contrast, the protocols of quantum cryptography are unconditionally secure. This particular aspect of quantum cryptography makes it very interesting. This chapter aims to provide a flavor of the intrinsic beauty of various aspects of secure quantum communication. Before we start a journey into the fascinating world of secure quantum communication, it would be apt to become familiar with the jargon used in this field and also with some interesting protocols of classical cryptography. Let us first do that.