Securing today’s communication networks against future quantum threats

Quantum computing looks set to revolutionise almost every industrial sector. Quantum computers can solve complex mathematical problems that cannot be tackled by traditional machines – or, if they were, would take thousands of years to complete. This increase in computing power alone will have ramifications across the globe.

It certainly affords new opportunities for telecommunications. New products such as Quantum Computing as a Service (QCaaS) could become prevalent, giving researchers and organisations access to quantum computing capabilities via the cloud.

There are many reasons to be excited about quantum technology. But, as we have seen above, quantum computers also threaten the effectiveness of current public key encryption techniques. The telecoms industry can adopt Quantum Key Distribution to create truly quantum-safe networks, ensuring sensitive data remains private even as new security challenges emerge.

‘Data in transit’ is one of the three ‘states’ of data, during which it requires specific protections. While the others, ‘at rest’ and ‘in use’, typically describe data housed in one location, data in transit is vulnerable to certain high-security threats like eavesdropping attacks and data theft while it’s in motion between points.

In order to secure data in transit against such attacks, networks need to be resilient against decryption attempts. That’s one reason why QKD technology is so successful at ensuring data security, as the quantum-secure data signals will alter when eavesdroppers are detected, meaning that the transmissions cannot be decrypted, and the network is secure.

‘Harvest now, decrypt later’ attacks are on the rise. Criminals are working to collect data which is currently encrypted using traditional cryptographic methods, with a view to accessing the sensitive information once quantum computers become commercially available.

These quantum computers already exist. Commercial, scalable quantum computing will soon be a reality. That’s why it’s vital for telecoms providers to transition to QKD as soon as possible. Only data which is encrypted using quantum-secure methods will be able to withstand decryption from a quantum computer, and any data transmitted via conventional methods is currently at risk of being harvested, and stored, for future decryption.

Optical fibres tend to degrade over time, which can reduce the strength of data signals, including the photons that make up the quantum signal. However, thanks to their high optical loss budgets, Toshiba QKD systems offer the headroom to accommodate potential fibre performance degradation while still conveying the quantum signal, thereby successfully transmitting quantum-secure keys and maintaining the quantum safety of the fibre link.

Integrating QKD into existing networks has traditionally required providers to use dedicated dark fibre cables alongside their original infrastructure to carry the QKD signal. This results in financial, logistical and operational expenses and takes significant time to deploy, which is why QKD multiplexing techniques that enable true QKD and data co-existence on the existing deployed fibre provides real and significant benefits to operators.

QKD signals are typically 100 million times weaker than those used to carry other forms of network data. It’s therefore challenging to preserve the quantum signal in the presence of multiple conventional data channels. In particular, scattering effects that result from the transmission of multiple, high power conventional data channels can potentially interfere with the quantum signals, making quantum key distribution impossible.

Multiplexing data with QKD information on the same fibre typically involves telecoms providers making trade-offs on a number of factors: the number of data channels multiplexed, the total optical launch power into the fibre, the QKD secret bit rate and the overall fibre transmission distance.

Our multiplexed (MU) QKD system places the quantum data channel in the O-Band (1310 nm), spectrally distant from the data channels in the C-band (1550 nm). This separation reduces scattering effects and potential interference.

As a result, it becomes possible to send QKD signals on fibres carrying multiple, conventional data signals, and to do so without impacting the performance of the existing optical network. Using this technique, existing deployed networks can be easily and incrementally upgraded to support QKD.

Toshiba’s multiplexed QKD systems are highly resilient, providing superior multiplexing performance across multiple data channels. With high optical launch power, it is possible to add additional channels without any impact on the overall performance of data or quantum channels.

This means that our multiplexed systems can be deployed on today’s fibre networks, running today’s data services, with the freedom to scale as needed.