For thousands of years, code-makers and code-breakers have been competing for supremacy. Their arsenals may soon include a powerful new weapon: quantum mechanics.
For thousands of years, code-makers and code-breakers have been competing for supremacy. Their arsenals may soon include a powerful new weapon: quantum mechanics. Cryptography — the art of code-making — has a long history of military and diplomatic applications, dating back to the Babylonians. In World World Two, the Allies ’ feat of breaking the legendary German code, Enigma, contributed greatly to the final Allied victory. Nowadays, cryptography is becoming increasingly important in commercial applications for electronic business and electronic commerce. 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. The most well-known application of cryptography is secure communication [1]. Suppose Alice would like to send a message to Bob, but there is an eavesdropper, Eve, who is wiretapping the channel. To prevent Eve from knowing the message, Alice and Bob may perform encryption, i.e., transform the message to something that is not intelligible to Eve during the communication. On receiving the message, Bob inverts the transformation and recovers the message (see figure 1). Bob’s advantage over Eve lies in his knowledge of a secret, commonly called the key, that he shares with Alice. The key tells him how to decode the message. For example: The rumble of Soviet tanks shook the Prague hotel room (number 117) as secret agent John Blond finished decoding his orders from his superior N. He tore the used page from the codebook and immediately burned it with his lighter. Blond is using a perfectly unbreakable cipher, a “one-time pad. ” The secret codebook allows N and Blond to share a long secret binary string — the key —
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?
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.