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shine a light

Engineers are on the brink of breaking a massive encryption barrier

The ultimate key is literally at your fingertips.

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Whether written invisibly with lemon juice or encrypted with complex math, secret messages are passed on through a myriad of bizarre and convoluted ways.

A team of engineers from China is introducing a new way to secretly transmit our most secret data or access secure locations using a tool that can be found on your person at any time: the human hand.

In their paper published Monday in the journal Proceedings of the National Academy of Sciences, the team demonstrated how infrared radiation (i.e. heat) coming from the hand can be used to not only decrypt secret messages but also to create passcodes that cannot be cloned or reproduced, granting unique access to information or locations with just a wave.

The integration would offer a power-free, multi-functional decryption system with intelligent human-machine integration — in other words, a powerful way to secure data that is controlled by the human body instead of a computer.

Your hand and a flashlight might not appear to have much in common, but engineers now have a new way for the human hand to shed light on hidden secrets.An et al. / PNAS

What’s new — Heat wafting off the human body has long been used for security and defense (e.g. to spot animals or other humans in the dark via night vision goggles,) but until now, write the authors, this infrared (IR) radiation had rarely been used as a way to actually put humans in control of such computerized systems.

This new way of connecting the human body with technology is reminiscent of fingerprint scanners today but would offer hands- and power-free opportunities for connection.

“The use of human components as IR light sources may provide a promising way to increase the controllability and flexibility of the engineered systems,” write the authors. “[T]he human hand is not just a natural and powerless IR light source, but also a multiplexed light source with each finger serving as an independent light source.”

Why it matters — Such a human-integrated system would not only offer a more sustainable approach to designing an encryption-decryption system (where information can be hidden and only accessed via a key or code,) but it could also help future proof encryption as well.

Today’s encryption protects everything from email passwords to NSA secrets from easy hacking by converting them from plain text into scrambled data that can be decrypted on the other side, but not at points in between. It largely relies on incredibly complex math that would take years or decades to hack to protect information from tampering, but quantum computers — which will have far superior processing power to classic computers — will be easily able to break into these systems by brute force.

Having immutable, physical encryption systems (like a hand, for example) offer new, robust avenues for encryption — which is only becoming more important as our lives and most sensitive information become increasingly digitized.

Here’s the background — If your hand is meant to be a beacon of light illuminating hidden mysteries, then why doesn’t it seem to glow when you look at it? It’s because the part of the electromagnetic spectrum that our hands (and whole bodies) “glow” in is outside of the visible range, meaning our eyes simply aren’t equipped to see it.

This electromagnetic range spans everything from large, low-frequency radio waves (like those sending tunes to your favorite FM station) to incredibly small and high-frequency gamma rays (like those inside atomic nuclei or the depths of space.)

Visible light — which captures all the colors that we see — ranges from 750 nanometers in wavelength to 380 nanometers and infrared light falls just outside this range with wavelengths between 1 millimeter to just above 750 nanometers.

But just because we can’t see the light that we emit, doesn’t mean it’s not there. Just as your hand looks unique to the human eye, its IR signature is unique as well. And because we effortlessly generate this light just by keeping our bodies at homeostasis, the authors write that it was the perfect candidate for a power-free decryption tool.

What they did — To transform the unremarkable human hand into a powerful decryption tool, the team only had to separate ambient infrared radiation (e.g. heat in a room) from the infrared radiation coming specifically from a hand. A kitchen scale is a good way to think about how this was done.

If your kitchen scale measured the weight of the mixing bowl as well as the flour you were adding, your recipe would be wildly off. Instead, bakers will tare their scales after setting down the mixing bowl (and before adding the flour) to superficially set the weight back to zero. This is essentially what the team did with their decryption system.

The team used a low-reflectivity polydimethylsiloxane spray on aluminum to encrypt a hidden message that was “tared” at ambient temperature, meaning any infrared radiation already in the room wouldn’t reveal it. But when additional infrared radiation was added via a hand, the hidden message or image could be revealed.

“When there is no hand, the coding pattern, including both the region of low IR reflectivity and region of high IR reflectivity, is in temperature equilibrium with the background... [meaning] the coding pattern is therefore not shown up in the IR image,” write the authors.
“[But] when the human hand is used as the light source, the IR emission from the hand is reflected by all the regions, and thus, the region of high IR reflectivity has a higher increase of IR radiance than that of low IR reflectivity, which leads to the differentiation of IR radiances and enables the decryption process.”
The decryption process works simply by applying extra infrared radiation to a reflective pattern. This slight change is enough to change the incident reflection of the infrared radiation and reveal the hidden image or data.An et al. / PNAS

The team found that using only the infrared light coming off a human hand they were able to reveal increasingly complex images, including those ranging across different depths (e.g. those with multiple layers of applied encrypted material.)

This discovery that the decryption process could be fine-tuned to work at different depths could be huge, write the authors, because it means that fingerprints (with their unique ridges and canyons) could be used as unclonable encryption keys.

From studying this system with American Sign Language as well, the team demonstrated that unique gestures could also be used as encryption keys as well, where every individual finger was a unique light source.

“The specific gesture composed of different fingers can thus be used as the matching key for information decryption as well, which increases the level of security in comparison to the use of the whole hand as the light source,” write the authors.

What’s next — There are still a lot of things that have to go just right for this technology to work, including nailing complex hand gestures or even having hands at the right temperature to contrast with the ambient heat (though the researchers say this can be easily fixed by rubbing your hands together to warm them up.) In the future, the researchers speculate that wearable detectors may be used to better capture these precise gestures.

Ultimately, the authors believe that this kind of technology could play a big role in increasing the intelligence and controllability of these encryption systems to put humans back at the helm of data protection.

Abstract: With the increasing pursuit of intelligent systems, the integration of human components into functional systems provides a promising route to the ultimate human-compatible intelligent systems. In this work, we explored the integration of the human hand as the powerless and multiplexed infrared (IR) light source in different functional systems. With the spontaneous IR radiation, the human hand provides a different option as an IR light source. Compared to engineered IR light sources, the human hand brings sustainability with no need of external power and also additional level of controllability to the functional systems. Besides the whole hand, each finger of the hand can also independently provide IR radiation, and the IR radiation from each finger can be selectively diffracted by specific gratings, which helps the hand serve as a multiplexed IR light source. Considering these advantages, we show that the human hand can be integrated into various engineered functional systems. The integration of hand in an encryption/decryption system enables both unclonable and multilevel information encryption/decryption. We also demonstrate the use of the hand in complex signal generation systems and its potential application in sign language recognition, which shows a simplified recognition process with a high level of accuracy and robustness. The use of the human hand as the IR light source provides an alternative sustainable solution that will not only reduce the power used but also help move forward the effort in the integration of human components into functional systems to increase the level of intelligence and achieve ultimate control of these systems.
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