Secure cryptography with real-world devices is now possible

July 27, 2022 – Research published this week in Nature explains how an international team of researchers from the UK, Switzerland and France have, for the first time, experimentally implemented a type of quantum cryptography considered “ultimate”, “Bug-proof means of communication.

One of the two ion traps used. Around the trap run a number of lines of laser beams for ion preparation and manipulation. At the front of the trap, the end of the quantum network link to the other trap – an optical fiber – is visible. Credit: David Nadlinger, University of Oxford.

Existing implementations of “quantum key distribution” (QKD) rely on communication between “trusted” quantum devices (and thus offer the potential for quantum hacking). The recently demonstrated approach enables secure communication between devices without needing to know much about them. This significant breakthrough paves the way for secure cryptography for real-world devices and other quantum information applications based on the principle of device independence.

The offer of quantum cryptography for greater security

Currently, secure cryptographic communication relies on the inability of traditional computers to calculate the prime factors of large numbers. However, as technology advances, future quantum computers can easily solve these problems, rendering current cryptographic protocols obsolete.

In an experiment based on three decades of fundamental research, experimental work at the University of Oxford – with theoretical contributions from ETH Zurich, EPFL, the University of Geneva in Switzerland and the French Commissariat aux Alternative Energy and Atomic Energy (AEC) – have demonstrated a comprehensive quantum key distribution protocol immune to the vulnerabilities and flaws in physical devices that plague current quantum protocols. Experience proves a much stronger form of security than is currently achievable using conventional computers.

Professor David Lucas from the University of Oxford explains: “The real breakthrough here is that we were not only able to show that our quantum network theoretically had sufficient performance to do this new type of QKD, but that we were actually able to do it. in practice and go as far as distributing a shared secret key. Although originally designed for quantum computing experiments, this shows the versatility of the quantum network for other applications.

Once two parties have obtained a secret key using device-independent quantum key distribution (DIQKD), they can use it for proven secure communication. To illustrate this in the experiment, the sender transmits to the receiver an encrypted image of John Stewart Bell, whose theoretical arguments about the limits of correlations in nature are central to device-independent security. Credit: David Nadlinger, University of Oxford; original image credited to CERN.

Independence of the device guaranteed

The multidisciplinary research team, made up of theoretical and applied physicists and computer scientists, succeeded in the experiment based on “high-quality quantum entanglement” or, in layman’s terms, an exclusive relationship between two particles that can extend over great distances (even light-years) in space, but still operate in tandem. Such connections provide broader security and privacy guarantees for communications and financial transactions without interference from third parties.

Previous work on QKD has already removed the assumption of limited computing power, but forced communicating parties to trust their quantum devices instead. The quantum key distribution demonstrated in this new research, however, can guarantee privacy with only a few general assumptions about the physical device used. The foundation of this “device-independent” scheme rests on the validity of quantum theory and can be certified by the measurement statistics observed during the experiment.

“Ninety years ago we thought that nature could not behave in such a curious way; sixty years ago we figured out how to show that it was after all; thirty years ago we discovered a way to harness this advantage,” says David Nadlinger, lead author of the Nature paper, “and now we can finally put that knowledge to the fundamental fabric of reality. in practice to secure communication”.

The importance of collaboration

As well as working with international partners, the University of Oxford leads the Quantum Computing and Simulation Hub (QCS), a collaboration between 17 UK universities that is part of a national program focused on promoting quantum technologies in the UK. United. Speaking of the breakthrough, Professor Lucas explains: “This has only been made possible by sustained investment from the UK’s National Quantum Technology Program, through the NQIT and QCS hubs – it requires many years of development to achieve the level of technical sophistication necessary for these experiments. ”

Source: University of Oxford

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