We report on the security analysis of time-coding quantum key distribution protocols. The protocols make use of coherent single-photon pulses. The key is encoded in the photon time-detection. The u...

Quantum Information and ComputationNov 1, 20110 citations

Quantum Information and Computation

Security analysis of the time-coding quantum key distribution protocols

Thierry Debuisschert, Simon Fossier

Published Nov 1, 2011• 1 citation

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Abstract

DOI: 10.26421/qic11.11-12-7

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Security analysis of the time-coding quantum key distribution protocols

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We report the security analysis of time-coding quantum key distribution protocols. The protocols make use of coherent single-photon pulses. The key is encoded in the photon time-detection. The use of coherent superposition of states allows to detect eavesdropping of the key. We give a mathematical model of a first protocol from which we derive a second, simpler, protocol. We derive the security analysis of both protocols and find that the secure rates can be similar to those obtained with the BB84 protocol. We then calculate the secure distance for those protocols over standard fibre links. When using low-noise superconducting single photon detectors, secure distances over 200 km can be foreseen. Finally, we analyse the consequences of photon-number splitting attacks when faint pulses are used instead of single photon pulses. A decoy states technique can be used to prevent such attacks.We report the security analysis of time-coding quantum key distribution protocols. The protocols make use of coherent single-photon pulses. The key is encoded in the photon time-detection. The use of coherent superposition of states allows to detect eavesdropping of the key. We give a mathematical model of a first protocol from which we derive a second, simpler, protocol. We derive the security analysis of both protocols and find that the secure rates can be similar to those obtained with the BB84 protocol. We then calculate the secure distance for those protocols over standard fibre links. When using low-noise superconducting single photon detectors, secure distances over 200 km can be foreseen. Finally, we analyse the consequences of photon-number splitting attacks when faint pulses are used instead of single photon pulses. A decoy states technique can be used to prevent such attacks.

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Security analysis of the time-coding quantum key distribution protocols

DebuisschertThierry, FossierSimon

Quantum Information and ComputationNov 1, 20110 citations

We propose quantum key distribution protocols based on coherent single-photon optical pulses with duration

T

and with minimum time-frequency uncertainty. The pulses are sent with possible delays (e.g., 0,

T∕2

) that are used to code the information (e.g., bit 0, bit 1) and that are shorter than the pulse width. Therefore, the time detection of the photons may result in a ambiguity of the delay evaluation for a potential eavesdropper. The duration of the received pulses is controlled thanks to a contrast measurement using an interferometer. A quantum formalism is given, allowing us to model the transmission of the key and the consequences of a possible eavesdropping. Two protocols are proposed and discussed. The first one involves two states and is limited to channels with losses lower than 50%. The second one involves four states, which prevents the eavesdropper from exploiting the losses of the line. The security of each protocol is evaluated as a function of channel losses, quantum bit error rate, and contrast loss in the case of intercept-resend attacks. It is applied to situations where photocounters dark counts are the main limitation of the system. The resulting maximum propagation distance allowing secure communication is evaluated.