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Technological advances in quantum computers and number theory have the potential to compromise the security of existing cryptographic protocols. Quantum key distribution (QKD) offers the possibility of information theoretic security and is theoretically unbreakable. Therefore it is the natural candidate to face the above digital threat.
However, in implementing QKD, it is important to check that the components employed do not deviate from their expected behaviour, to avoid opening the door to new security loopholes [1]. For this reason, it is necessary to characterise the real behaviour of the components, build reliable models and include them in the security analysis.
Here we introduce a set of techniques and measurements to ease this characterisation process. We discuss explicit examples applied to the source [2], the boundaries [3] and the detection unit [4] of a QKD apparatus. These methods pave the way to the future certification of QKD systems.
[1] K. Tamaki, M. Curty, and M. Lucamarini, “Decoy-state quantum key distribution with a leaky source,” New J. Phys 18, 65008 (2016).
[2] J. F. Dynes et al., “Testing the photon-number statistics of a quantum key distribution light source,” arXiv:1711.00440 (2017).
[3] M. Lucamarini et al., “Practical Security Bounds Against the Trojan-Horse Attack in Quantum Key Distribution,” Phys. Rev. X 5, 031030 (2015).
[4] A. Koehler-Sidki et al., “Setting best practice criteria for self-differencing avalanche photodiodes in quantum key distribution,” SPIE Proc. 10442, Quant. Inf. Sci. Tech. III, 104420L (2017).
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