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Optical Fiber Communication Conference

Quantum key distribution the science of secret communications

Richard Hughes

Published Jan 1, 2005• 0 citations
Publisher

Abstract

Quantum key distribution (QKD) uses single photon communications to securely transfer cryptographic keys that are required for secure communications. I will describe the theory of QKD and its implementation in both optical fiber and free-space.
DOI
10.1109/ofc.2005.192866

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Quantum Key Distribution (QKD) is used in Quantum Cryptographic Systems to exchange secret key between parties who need to communicate secretly. Such a key can be used with a symmetric encryption schemes to establish a secure communication. Until recently, QKD is possible using optical fiber over few tens of kilometers but not more due to single photons getting absorbed by the fiber. There are no commercial wireless quantum crypto products yet, but QKD will soon be used in wireless medium from satellite to the earth so we could get 10,000 miles. But wireless medium brings its own problems. The energy transmitted via a wireless link spreads out, leading to higher and varying transmission losses, ambient daylight, or even light from the moon at night couple into the receiver, leading to a higher error rate. Interference from other photon sources air with clouds, dust and unsettled conditions creates intervention. In this paper, different techniques for communication in Quantum Cryptography using wireless networking infrastructure are discussed.
The secure distribution of the secret random bit sequences known as {open_quotes}key{close_quotes} material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is an emerging technology for secure key distribution with single-photon transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non-orthogonal single-photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. In our optical fiber experiment we have performed quantum key distribution over 24-km of underground optical fiber using single-photon interference states, demonstrating that secure, real-time key generation over {open_quotes}open{close_quotes} multi-km node-to-node optical fiber communications links is possible. We have also constructed a quantum key distribution system for free-space, line-of-sight transmission using single-photon polarization states, which is currently undergoing laboratory testing. 7 figs.
Despite the challenges, several researchers from academia, business, and government are conducting extensive research and development on quantum key distribution (QKD), a symmetric secret key that secures the secrecy of quantum communications. A QKD network is made up of two or more QKD nodes connected by optical fiber or open space. To ensure long-term security and forward secrecy, secret keys are negotiated between any two QKD nodes before being given to many users in multiple locations. In actuality, most QKD algorithms communicate across two separate channels. There are two channels: classical for QKD and quantum for quantum communication. This work offers a single-channel QKD technique for both traditional and quantum communication. To our knowledge, there is no single channel source validated QKD protocol in the literature. This study provides the foundation for the verified source of QKD.
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The secure distribution of the secret random bit sequences known as 'key' material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is a new technique for secure key distribution with single-photon transmissions: Heisenberg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non- orthogonal photon polarization states to generate shared key material over line-of-sight optical links. Key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. We have developed and tested a free-space quantum key distribution (QKD) system over an outdoor optical path of approximately 1 km at Los Alamos National Laboratory under nighttime conditions. Results show that free-space QKD can provide secure real-time key distribution between parties who have a need to communicate secretly. Finally, we examine the feasibility of surface to satellite QKD.
The secure distribution of the secret random bit sequences known as `key' material, is an essential precursor to their use for the encryption and decryption of confidential communications. Quantum cryptography is an emerging technology for secure key distribution with single-photon transmissions: Heisenburg's uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). We have developed experimental quantum cryptography systems based on the transmission of non-orthogonal single-photon states to generate shared key material over multi-kilometer optical fiber paths and over line-of-sight links. In both cases, key material is built up using the transmission of a single- photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. In our optical fiber experiment we have performed quantum key distribution over 24-km of underground optical fiber using single-photon interference states, demonstrating that secure, real-time key generation over `open' multi-km node-to-node optical fiber communications links is possible.