WHY THIS MATTERS IN BRIEF
As the rise in the number of connected devices and systems is out paced only by the rise in #cyber attacks, researchers have found a new way to identify individual systems at the quantum level.
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One thing that everyone agrees on is that in the future trust, if not just because of the emergence of DeepFakes and new synthetic content tech, and security, as we connect more and more people, things and devices together, especially in the era of the Internet of Things (IoT) and wearables, are going to get exponentially more difficult to guarantee and protect. But now, certainly when it comes to the latter, a new breakthrough might just help create the ultimate trust, security, and authentication system – a system that can, with a cast iron guarantee, prove that the person or thing you are communicating with are the real deal and not some dodgy faker.
We might imagine that electric current flows as a smooth, even stream of electrons through our electronics devices, but at the quantum scale the flow of electric current might be more accurately pictured as a bubbling brook containing many tiny ripples. These ripples can be caused by single-electron effects, which arise due to the repulsion among electrons confined in very small spaces, such as trap sites in transistors. Single-electron effects can lead to tiny changes in the current-voltage characteristics of these devices.
As trap sites are basically tiny defects that are randomly distributed in an uncontrollable way during fabrication, the number, location, and energy levels of trap sites differ for every transistor. As a result, single-electron effects lead to a unique modification in the current-voltage characteristics, effectively giving each transistor a unique “fingerprint.”
Recently, researchers have been investigating how these so called “Quantum fingerprints” might one day be used as an inexpensive form of ID to protect users’ personal information and systems against the emerging threats posed by the IoT and cyber criminals.
In a new paper published in Applied Physics Letters, physicists T. Tanamoto and Y. Nishi at the Toshiba Corporation in Kawasaki, Japan, and K. Ono at RIKEN in Saitama, Japan, have demonstrated that single-electron effects may be detected by image-recognition algorithms and used for computer chip identification and security.
“So far, no widespread application exists for single-electron devices,” says Tanamoto. “Our research opens a different way of using the single-electron effect – as a security device. The importance of security is increasing day by day.”
As the physicists explain, the fingerprint of an electronic device can be thought of as a Physically Unclonable Function (PUF). Like a human fingerprint, PUFs are based on unique, naturally occurring physical variations and cannot be transferred to other devices. In addition, PUFs retain their key features throughout the lifetime of the device, despite some degradation due to aging effects.
In their work, the physicists applied image-matching algorithms in order to identify different current-voltage features called Coulomb diamonds. The Coulomb diamonds are so-named because the regions of a current-voltage diagram in which current is suppressed by single-electron effects sometimes have the shape of a diamond. As the number of trap sites increases, the diamond patterns because more complex.
Just as human fingerprints change depending on conditions, such as being wet, dry, or oily, the Coulomb diamond images can also look slightly different when measured under different conditions. Despite these variations, the researchers demonstrated that currently available feature detection and image-matching algorithms could successfully extract the key features, such as corners and edges, and distinguish between different Coulomb diamonds.
One of the advantages of the method is that, although an average computer chip today contains more than a billion transistors, just a single transistor is needed to generate the fingerprint for the entire chip meaning that this method could be applied to literally every chip and everything since everything has its own unique quantum fingerprint whether it’s a diamond, a computer chip, or someone’s fingernail. This makes it potentially feasible to use this method for a wide range of devices and applications.
On the other hand, there are still challenges that remain before implementing the method. For one thing, the Coulomb diamonds, for example, were measured at cryogenic temperatures of around 1.5 degrees above Absolute Zero. And while previous research has shown that it’s possible to measure single-electron effects at room temperature, at the moment doing this requires expensive fabrication processes.
In the future though those challenges and costs will be overcome, and the physicists say they plan to explore other ways of fingerprinting transistors in the meantime.
One possibility is to measure the spin-qubit behaviors of electrons in traps, as these quantum behaviours are expected to be affected by the traps. As with single-electron effects, the unique and random distribution of traps in transistors is expected to result in a unique fingerprint for each transistor. Going forward, the researchers would also like to investigate ways to implement transistor fingerprint security into future quantum computers, the unhackable quantum encryption systems for which, notably, were hacked by hacked by Chinese researchers.
“Quantum computers are one of the hottest issues right now,” Tanamoto said. “We would like to combine our quantum PUF into the security system of quantum computers in the future.”