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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

A quantum jump in security

Hoi‐Kwong Lo

Published Dec 12, 2003• 0 citations

Abstract

ABSTRACT Q uantum mechanics can revolutionize the art of code-making by breaking standard encryption schemes and by making unbreakable codes. In this document, I survey the motivation, power and limitation of quantum code-making. * Keywords: Quantum computing, quantum information, quantum cryptography, security, key distribution,cryptography 1. INTRODUCTION Human desire to keep written messages secret is almost as old as writing itself. Indeed, cryptography—the artof code-making—dated back to the Babylonians. For thousands of years, code-makers and code-breakers have engaged in an escalating arms race with each other.' Cryptographers do not sleep well. Every innovation in code-making has so far been defeated by new innovation in code-breaking with disastrous consequence tothe unsuspecting users of those insecure codes. For instance, Queen Mary of Scotland was executed by QueenElizabeth following the decoding of encrypted communications between Queen Mary and her conspirators whichprovided the irrefutable proof of her quilt in plotting against Queen Elizabeth. In the Second World War, thebreaking of the legendary German Engima code by the Allied code-breakers contributed significantly to theoutcome of the war. In cryptography, one must expect the unexpected and even the unthinkable.Q uantum mechanics has made a recent entry in this life and death struggle between code-makers and code-23 In this document, I will address the following frequently asked questions:(1) What quantum code-breaking can do?(2) What quantum code-making can do?(3) What quantum code-making cannot do?

DOI: 10.1117/12.543335

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Cryptography—the art of code-making—has a long history of military and diplomatic applications, dating back to the Babylonians. In World War II, the Allies' feat of breaking the legendary German code Enigma contributed greatly to their final victory. Nowadays, cryptography is becoming increasingly important in commercial applications for electronic business. Sensitive data such as credit card numbers and personal identification numbers (PINs) are routinely transmitted in encrypted form. Quantum mechanics is a new tool for both code-breakers and code-makers in their eternal arms race. It has the potential to revolutionize cryptography both by creating perfectly secure codes and by breaking standard encryption schemes.

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In a series of recent experiments a radical new technique has been demonstrated that could have far-reaching consequences for the way in which the confidentiality and integrity of our networks is protected. This technique, known as quantum cryptography, is the result of a synthesis of ideas from fundamental quantum physics and classical encryption and has lead to a radical new approach to the business of secure communications. We review the origins of and developments in this rapidly growing field and assess the current status of both the theory and the experiments.

Ever since its inception, cryptography has been caught in a vicious circle: Cryptographers keep inventing methods to hide information, and cryptanalysts break them, prompting cryptographers to invent even more sophisticated encryption schemes, and so on. But could it be that quantum information technology breaks this circle? At first sight, it looks as if it just lifts the competition between cryptographers and cryptanalysts to the next level. Indeed, quantum computers will render most of today’s public key cryptosystems insecure. Nonetheless, there are good reasons to believe that cryptographers will ultimately prevail over cryptanalysts. Quantum cryptography allows us to build communication schemes whose secrecy relies only on the laws of physics and some minimum assumptions about the cryptographic hardware—leaving basically no room for an attack. While we are not yet there, this paper provides an overview of the principles and state-of-the-art of quantum cryptography, as well as an assessment of current challenges and prospects for overcoming them.