Developments towards practical free-space quantum cryptography

We describe a free space quantum cryptography system which is designed to allow continuous unattended key exchanges for periods of several days, and over ranges of a few kilometres. The system uses a four-laser faint-pulse transmission system running at a pulse rate of 10MHz to generate the required four alternative polarization states. The receiver module similarly automatically selects a measurement basis and performs polarization measurements with four avalanche photodiodes. The controlling software can implement the full key exchange including sifting, error correction, and privacy amplification required to generate a secure key

Practical quantum cryptography for secure free-space communications

Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics and information-theoretically secure post-processing methods. An adversary can neither successfully tap the quantum transmissions, nor evade detection, owing to Heisenberg's uncertainty principle. In this paper we describe the theory of quantum cryptography, and the most recent results from our experimental free-space system with which we have demonstrated for the first time the feasibility of quantum key generation over a point-to-point outdoor atmospheric path in daylight. We achieved a transmission distance of 0.5 km, which was limited only by the length of the test range. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on orbit. We present a feasibility analysis of surface-to-satellite quantum key generation.Comment: 12 pages, 4 figure

Practical quantum cryptography for secure free-space communications

Quantum Cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics and information – theoretically secure post- processing methods. An adversary can neither successfully tap the quantum transmissions, nor evade detection, owing to Heisenberg’s uncertainty principle. In this paper we describe the theory of quantum cryptography and the most recent results from our experimental free space system with which we have demonstrated for the first time the feasibility of quantum key generation over a point-to-point outdoor atmospheric path in daylight. We achieved a transmission distance of 0.5km which was limited only by the length of the test range. Our results provide strong evidence that cryptographic key material could be generated on the demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on orbit. We present a feasibility analysis of surface-to-satellite quantum key generation

Enhancing security in quantum cryptography

Quantum Key Distribution was named as one of the top ten emerging technologies by Technology Review Journal in 2003 in their annual edition. The growth in quantum cryptography since the beginning of the millennium has been expedited by new theories and ideas. The introduction of practical quantum cryptosystems offered by USA based company MagiQTech and its European rival idQuantique has changed the face of cryptography. With active experimental research in USA, Europe, Japan and Singapore, the scope of quantum cryptography seems to be growing daily. When Bennett and Brassard proposed their BB84 protocol in Bangalore in 1984, no one would have guessed the quantum revolution they had launched. Since then, new protocols have been proposed and new theories developed, but BB84 remains the simplest and probably the easiest to implement. Now that the practical implementation of basic quantum cryptography has been achieved, one can be almost certain that new protocols will sooner or later be tested for the efficiency they could provide. We have developed a Classical Authentication Aided (CAA) protocol, which merges the classical authentication policies with quantum transmission to make it even more secure. With the complexities of the authentication policies and the bit to qubit conversion, our system becomes a complex one. We also discuss the possibilities of free space quantum transmission of the protocol instead of only through optical fiber

Quantum cryptography: key distribution and beyond

Uniquely among the sciences, quantum cryptography has driven both foundational research as well as practical real-life applications. We review the progress of quantum cryptography in the last decade, covering quantum key distribution and other applications.Comment: It's a review on quantum cryptography and it is not restricted to QK