This book is designed to serve as a reference book for researchers. The book is primarily deals with the introductory concept of Quantum Cryptography. The various protocols used in the Quantum Key Distribution (QKD) is also discussed in this book. The Salient features of this book: - Concept of Quantum Cryptography - Protocols used in Quantum Key Distribution (QKD) - Security Analysis of QKD Protocols - BB84 Protocol and its Implementation