Abstract
Satellite-mediated quantum key distribution (QKD) is set to become a critical technology for quantum-secure communication over long distances. While satellite QKD cannot be effectively eavesdropped, we show it can be disrupted (or ‘jammed’) with relatively simple and readily available equipment. We developed an atmospheric attenuation and satellite optical scattering model to estimate the rate of excess noise photons that can be injected into a satellite QKD channel by an off-axis laser, and calculated the effect this added noise has on the quantum bit error rate. We show that a ground-based laser on the order of 1 kW can significantly disrupt modern satellite QKD systems due to photons scattering off the satellite being detected by the QKD receiver on the ground. This class of laser can be purchased commercially, meaning such a method of disruption could be a serious threat to effectively securing high-value communications via satellite QKD in the future. We also discuss these results in relation to likely future developments in satellite-mediated QKD systems, and countermeasures that can be taken against this, and related methods, of disruption.
Highlights
Rapid developments in quantum computing threaten the forward security of public key cryptography that currently underpins secure communication and trade
Along with the necessary optics and tracking mount, a system able to target a satellite and disrupt its Quantum key distribution (QKD) transmission can be assembled for under $200,000 USD, meaning that the means to disrupt satellite QKD are available to even small groups with modest resources. This poses a serious threat to the use of satellite-mediated QKD in the future, and we identify measures that future satellite QKD systems could employ to reduce their susceptibility to this type of disruption
While the complete additional QBER calculation for the scenario where a satelliteborne QKD receiver is directly targeted by the laser terminal is not carried out here due to the lack of a reliable scattering model for this scenario, from the scattering experiments described in Section 2.2 which showed on the order of one in 107 photons incident on the QKD optic couple into the QKD receiver, we expect that complete disruption of the QKD link in this scenario will be achieved with significantly lower laser powers than for the case where the laser power must scatter off the satellite and into the receiver at the ground station
Summary
Rapid developments in quantum computing threaten the forward security of public key cryptography that currently underpins secure communication and trade. As QKD technology matures to enable practical key rates over long distances, it will become of extreme importance to areas such as finance, government operations, and defence. A great deal of effort is being expended in developing practical QKD technologies around the world, and rapid progress is being made on many fronts [2]. Due to link attenuation and the impossibility of noiselessly amplifying quantum states, QKD via terrestrial optical fibre links is currently limited to a few hundred kilometres [3,4]. That extend the reach of QKD systems via entanglement swapping [6], are being developed, but these technologies have not yet matured to a practical level
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