Quantum Conference Key Agreement

Abstract

Quantum cryptography offers new methods of secure communication. Unlike traditional classical cryptography, which employs various mathematical techniques to restrict eavesdroppers from learning the contents of encrypted messages, quantum cryptography is focused on the physics of information. The process of sending and storing information is always carried out by physical means, for example photons in optical fibers or electrons in electric current. Eavesdropping can be viewed as measurements on a physical object—in this case the carrier of the information. What the eavesdropper can measure, and how, depends exclusively on the laws of physics. Using quantum phenomena, we can design and implement a communication system that can always detect eavesdropping. This is because measurements on the quantum carrier of information disturb it and so leave traces. What follows is a brief overview of the quest for constructing unbreakable ciphers, from classical to quantum.