Singapore Adopts Quantum Key Distribution. Is the technology mature enough?

Singapore today 🇸🇬. Singtel (Singaporean telecommunications conglomerate), in partnership with ID Quantique (quantum cybersecurity company), is launching the Nationwide Quantum Safe Network Plus (NQSN+). This project integrates Quantum Key Distribution (QKD) as a backbone for the creation of key material in the network. Access to the network is offered as a Quantum-Safe-as-a-Service model. Details on the number of participating organizations have not yet been disclosed.

As quantum key distribution (QKD) advances toward becoming a production-ready technology, several limitations persist due to the current stage of development. A key challenge is the reliance on trusted nodes that decrypt and re-encrypt messages, along with the relatively short distance between QKD nodes, typically limited to around 50 km. While this distance limitation poses less of an issue in geographically compact countries like Singapore, the continued need for trusted nodes adds complexity to achieving the desired level of security in physical implementations of the technology. As a result, QKD networks are not always practical for every scenario. However, for specific cases like the NQSN+ use case, QKD seemed to be a suitable solution.

Looking at the broader landscape of QKD's current state, future potential, and ongoing discussions about its evolution, the stages outlined in RFC9583 offer a clear roadmap for building more secure QKD networks. These stages describe the technological advancements needed to eliminate the reliance on trusted nodes by placing QKD directly in user devices and enabling long-range communication.

Stage 1: Secure communication through QKD with trusted nodes represents the current state of the technology. In this model, nodes decrypt and re-encrypt messages as they pass through the network. The requirement to handle unencrypted messages at these nodes introduces significant security challenges in practical implementations.

Stage 2: Secure communication using end-to-end QKD. This stage requires the development of prepare-and-measure technology that can be integrated into user devices. Once this is achieved, users will effectively become trusted nodes themselves. However, distance limitations will persist, and some trusted nodes will still be necessary in the broader network.

Stage 3: Secure communication using entanglement-enabled QKD. To reach this stage, advancements in entanglement distribution are required. This technology will enable the development of quantum repeaters that "amplify" the signal without the need for decoding and re-encoding, enhancing the overall efficiency and security of the system.

In summary, while QKD has made significant strides, further technological development is necessary to expand its use cases and improve its security. Achieving these next stages will unlock the full potential of QKD networks, allowing for broader implementation and greater long-distance communication capabilities.

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