Abstract
Quantum key distribution’s (QKD’s) central and unique claim is information theoretic security. However there is an increasing understanding that the security of a QKD system relies not only on theoretical security proofs, but also on how closely the physical system matches the theoretical models and prevents attacks due to discrepancies. These side channel or hacking attacks exploit physical devices which do not necessarily behave precisely as the theory expects. As such there is a need for QKD systems to be demonstrated to provide security both in the theoretical and physical implementation. We report here a QKD system designed with this goal in mind, providing a more resilient target against possible hacking attacks including Trojan horse, detector blinding, phase randomisation and photon number splitting attacks. The QKD system was installed into a 45 km link of a metropolitan telecom network for a 2.5 month period, during which time the system operated continuously and distributed 1.33 Tbits of secure key data with a stable secure key rate over 200 kbit/s. In addition security is demonstrated against coherent attacks that are more general than the collective class of attacks usually considered.
Highlights
Quantum Key Distribution[1] (QKD) is well known for its unique information theoretic security, which does not depend on the resources available to an eavesdropper
The transmitter is installed in a server rack at the central location and connected to the receiver in the western location by two fibres from the cable; one is used for quantum signals and the second for all other communication data, such that no external network connection is required for the QKD system to operate
The fibre is of standard SMF-28 type with a total characterised loss of 14.5 dB, equivalent to 0.33 dB/km – this is increased compared to the typical laboratory fibre loss of 0.2 dB/km mainly due to splice and other connector losses
Summary
Quantum Key Distribution[1] (QKD) is well known for its unique information theoretic security, which does not depend on the resources available to an eavesdropper. Countermeasures should ideally be connected to the system security proof via testable assumptions – this is done for example with decoy states, phase randomisation characterisation and recently for Trojan horse optical components[20, 21]. Some of these attacks are well-known; for example the photon number splitting attack (which can be mitigated using the decoy state protocol) and detector control attacks[22,23,24,25]. It is worth clarifying that reports of attacks breaking the security of QKD www.nature.com/scientificreports/
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