Why the time is now to implement Quantum-safe networks

By Dr Andrew Shields, Head of the Quantum Technology Division, Toshiba Europe
The WEF predicts 20 billion devices will need to be upgraded or replaced to support new forms of quantum-resistant encryption over the next two decades

At Mobile World Congress in September, Luke Ibbetson, head of R&D at Vodafone, said: “Quantum computing is by far the biggest revolution in computing since the 1950s.” This is not an overstatement. Quantum computers will be capable of easily performing calculations beyond the capabilities of classical computers, including those involved in cracking public key cryptography algorithms. These encryption techniques are used to protect much of our valuable data today – from WhatsApp messages to bank transfers. What happens when these fortresses come down?

Telecoms providers, who are responsible for ensuring the security of the network, are at the forefront of this discussion. But even as the threat of quantum computing evolves from theory to reality, creating a quantum-safe network has proven an ongoing challenge. Solutions have always come with a significant downside: either a huge bill for overhauling an entire network, or compromises to the distance and performance of existing networks. With new innovation in the field, all this is about to change.

A growing threat

Quantum computers have been discussed in academic circles since the early 1980s. Despite ongoing research, however, they remained a pipe dream until private investment accelerated innovation over the last few years. Understandably, conversation about the threat such computers posed to cybersecurity had always felt somewhat academic.

Thanks to a recent innovation arms race, organisations across the globe have competed to realise the computational benefits of quantum, with IBM releasing the first integrated quantum computing system in 2019 - IBM Quantum System One. Shortly after, Google’s 54-qubit Sycamore processor completed a computation in 200 seconds that would have taken the most powerful classical supercomputer in the world 10,000 years.

Today, quantum computers not only exist, but Fujitsu predicts that it will make its first commercially available quantum computer just next year.

There is understandably huge excitement about the possible benefits of quantum computing, including increasing the accuracy of molecular simulation, making drug-design and discovery faster and less expensive. However, such benefits are counterbalanced by the fact that once the technology is available on the commercial market, it will no longer be controlled and its power can be put to nefarious means.

In fact, malicious actors have already begun collecting data protected by traditional public-key cryptography in ‘harvest now, decrypt later’ attacks: already, they are anticipating the commercial availability of quantum computers, which will allow them to crack it. As we reach the brink of this reality, there has been increasing alarm from academics and industry bodies about creating quantum-safe technologies.

Quantum-safe solutions

In July, The US National Institute of Standards and Technology (NIST) selected four encryption algorithms that it believes will be more resilient to the known quantum computing algorithms. The World Economic Forum predicts that over the next two decades 20 billion devices will need to be upgraded or replaced to support new forms of quantum-resistant encryption[1].

Beyond this, the network itself is a central focus for resisting the threat by protecting data while it’s in transit. A huge amount of investment and research has gone into the problem of how to create quantum-safe networks; here, Quantum Key Distribution (QKD) has proven an exciting field.

QKD technology takes advantage of the laws of quantum physics to ensure that bad actors cannot decrypt data in transit even with the use of powerful new quantum computers, while still maintaining security against other high-performance computers.

For telecoms providers, QKD technology offers a way to protect customers from current and future cyber security threats. However, integrating QKD into existing networks has traditionally presented complications, including the need to introduce dedicated dark fibre cables alongside original infrastructure to carry the QKD signal. 

Implementing additional dark fibres might be feasible for some sections of the network, but metro and “access tail” environments – which are often built-up locations such as cities – present a significant challenge: it would be expensive for telecoms providers to use dedicated fibres within the metro segment of the network. Such obstacles have prohibited many providers from being able to move quickly on the installation of quantum-safe technologies.

Multiplexing: opportunity and obstacle

Wavelength division multiplexing (WDM) is a common technique used in fibre optic networks that involves placing many different optical data wavelength channels on the same fibre, greatly increasing the fibre’s data carrying capacity.

WDM – or simply ‘multiplexing’ – is the simplest solution to integrating QKD onto telecoms providers’ existing fibre, with the secret encryption keys transmitted on the fibres that are already carrying conventional telecoms data services.

In the past QKD has typically been implemented on dedicated fibres. However, dark fibre can be a scarce and valuable commodity, especially within metro networks. The dedicated fibres required for QKD in the past could be more profitably employed for customer data, or in some circumstances may not be available at all. The ability to combine QKD and data signals on common fibres using WDM is the key to the puzzle for telecoms operators. 

From possible to viable

New technologies are giving hope to the cause, just as the threat of quantum draws nearer. Toshiba has been pioneering quantum-safe solutions for decades, but we’ve now discovered a technique that will enable multiplexing on the same fibre, without compromising performance.

Although it is possible to multiplex QKD signals into the C-band (around a wavelength of 1550nm) conventionally used for data traffic, best performance is achieved placing the quantum channel in the O-band at 1310nm. This allows for a degree of spectral separation between the QKD (at 1310nm) and conventional data signals (around 1550nm) within the optical fibre, allowing more effective filtering of the noise created by the strong data signals.

While QKD over dedicated fibres has been available for some time, this innovation makes QKD economically viable for the first time, even for the access tails to the customer. Using this system, it’s possible to easily implement QKD to an existing network infrastructure, without the need to introduce new fibres for the quantum signals – radically reducing the cost of making a current infrastructure quantum-safe. Meanwhile, using this brand-new multiplexing technique, providers can maintain existing performance standards too.

Two factors have converged to make this a uniquely important time for telecoms providers to plan to adapt their infrastructure. Rapid advances in quantum computing mean that the threat to cybersecurity has become more real and pressing. Meanwhile, for the first time, new multiplexing technology makes it viable for telecoms providers to integrate QKD without choosing between a prohibitively expensive overhaul to install dedicated dark fires, or impaired performance with previous types of multiplexing.

With this exciting new innovation, telecoms providers can protect their existing network against the future quantum threat, while still delivering the transmission distance and speed that their customers demand.

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