In Focus Network Security

Quantum Key Distribution in the GÉANT network, is it possible?

As the internet and other communication networks continue to grow and evolve, it is becoming increasingly important to find secure and reliable communication methods that can meet modern demands.

Quantum Key Distribution (QKD) has emerged as a promising answer to this call. QKD enables perfectly secure cryptographic keys to be exchanged between two parties and can provide security guarantees against eavesdropping attempts. How? Single photons encode information that are transmitted using quantum mechanical principles. Streams of photons are then sent across fibre connections from which cryptographically sound keys can be distilled.

The use of QKD has been the subject of significant research and development in recent years, with particular attention paid to addressing the challenges associated with implementing QKD such as long-distance communication and the need for sufficiently high key rates. This has led to the development of various QKD systems.

To investigate the applicability of QKD in the GÉANT network, a study was conducted over a nine-month period. The study focused on the co-existence of data waves and QKD traffic on a shared fibre medium and included a quantitative analysis of the performance of QKD equipment. The results of the study showed that key exchange could take place at attenuation levels of up to 23.5dB. Currently, this would allow for QKD to be deployed in approximately 35% of the fibre spans in the GÉANT network.

If dedicated dark fibre is used instead of shared fibre, this percentage is expected to increase to approximately 90%. This is because dedicated dark fibre allows for QKD to be performed at 1550nm. This wavelength is commonly used for data transmission and has a lower level of attenuation per km of fibre.

As part of the research, a technical feasibility analysis of QKD on the western ring of the network was performed, where the percentages of fibre spans that could currently support QKD were slightly lower, at 30% and 85%. This was found to be caused by the high levels of attenuation that are experienced on links that cross the English Channel.

Map of Europe, displaying the applicability of QKD on the western ring of the GÉANT network. PoPs are shown as blue squares, amplifier stations as magenta triangles. Lines that are either red, orange, or green connect all points, corresponding to the level of attenuation on the link span.
Map of the western ring, visualising the link spans that could be covered with QKD equipment. Green links could be multiplexed with data waves, orange links would require a dedicated dark fibre. Red links would require alternative approaches to QKD.

Overall, the study provides valuable insights into the technical applicability of QKD, highlighting the potential for QKD to be a secure and reliable communication method in this context. The full paper can be found here, which also includes an analysis of existing standardisation efforts related to QKD and QKD networks.

The research was performed by Karel van Klink during an internship at GÉANT in the Network Evolution team. The outcome of this internship is a master’s thesis in Internet Science & Technology at the University of Twente. For any queries regarding this research, please contact Karel van Klink at GÉANT.

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