The quantum nature of cryptography

Gilles Brassard A

Charles H. Bennett

We review the goals of cryptography, explain how quantum laws allow some of these goals to be attained that could not be otherwise, and comment on the future of quantum cryptography and the nature of its security.

Erik Kreifeldt

Richard Hughes, Douglas M. Alde, P. L. Dyer +3 more

Quantum cryptography is a new method for secret communications offering the ultimate security assurance of the inviolability of a law of nature. In this paper we shall describe the theory of quantum cryptography, its potential relevance and the development of a prototype system at Los Alamos, which utilizes the phenomenon of single-photon interference to perform quantum cryptography over an optical fibre communications link.

Sellami Ali, Khalid A. Saeed Al-Khateeb

S. N. Molotkov

The prototype of a new quantum cryptosystem is described. Such a cryptosystem is naturally called time-shift quantum cryptography. It realizes all basic quantum-cryptography protocols [BB84, B92, BB84(4+2)] in a common fiber-optic system. This scheme does not involve Mach-Zehnder interferometers, which enables one to naturally realize the multiplex mode of secure key distribution and to naturally integrate this quantum-cryptography scheme into traditional fiber-optic telecommunication systems. The proposed time coding method in quantum cryptography makes it possible to significantly simplify experimental schemes and to exclude the finest fiber-optic part, the interferometer. In essence, the fundamental difference of the time coding method from the phase coding method is that the part using phase relations in superposition between “parts” of a quantum state is eliminated from the phase-coding method, and only the part using the time division principle is retained. The time division principle is common for both methods and is minimally necessary, in contrast to the phasecoding method, which can be excluded altogether. The proposed scheme is briefly compared with the two most developed phase-coding schemes (without self-compensation and with passive self-compensation).