Handbook of Information Security: Information Warfare, Social, Legal, and International Issues and Security Foundations, Volume 2

Quantum Cryptography

G. Massimo Palma, Università degli Studi di Milano, Italy

Introduction

Public Versus Private Key Cryptosystems

The Photon Polarization and the Rules of Quantum Mechanics

Classical Polarization

Quantum Polarization

Nonorthogonal States Quantum Key Distribution Protocols

Quantum Eavesdropping

Entanglement-Based Quantum Key Distribution Protocol

Suggestions for Further Reading

Glossary

Cross References

References

INTRODUCTION

Quantum cryptography is the name under which are commonly known those techniques that make use of the laws of quantum mechanics to prevent the unauthorized access to secret information. The most celebrated of such protocols, whose description is the main scope of this section, is quantum key distribution, undoubtedly the most successful quantum information processing protocol from the technological viewpoint. Quantum key distribution is a scheme that allows two remote parties to share a common secret random string of bits even in the presence of an adverse party who tries to eavesdrop. As discussed shortly, it solves the problem of secure distribution of private cryptographic keys by allowing the detection of any eavesdropping.

Quantum key distribution is historically the first quantum information processing protocol. Some of the ideas behind it were implicitly suggested by Stefan Wiesner, who proposed “quantum tokens which cannot be forged,” later published in Wiesner (1983). The first quantum cryptographic protocol, however, was put forward ...