Researchers at the University of UNSW Sydney and Monash University have demonstrated a communication method that hides data transfers inside natural thermal radiation.
Every object emits faint infrared radiation from heat. Thermal cameras can detect it, but the human eye can’t. Instead of adding a brighter signal, the system subtly reduces that glow. The change blends into the normal background radiation, making the data transmission difficult to detect.
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New ways to protect data
Dr Michael Nielsen from the UNSW Sydney explains, “Data is so ubiquitous nowadays, but we’re not necessarily coming up with new ways to protect that data. We do have encryption methods, but at the same time we’re always having to create new encryption methodologies when bad actors find new decryption strategies.”
The research group built a device called a thermoradiative diode (pictured above) that can rapidly switch between slightly brighter and darker infrared states, a pattern that encodes information. To outside observers the signal blends into natural infrared noise, so it appears like nothing unusual is happening.
“If someone doesn’t even know the data is being transferred, then it’s really very hard for them to hack into it,” Nielsen said. “If you can send information secretly then it definitely helps to prevent it being acquired by people you don’t want to access it.”
Early laboratory tests transferred data at roughly 100 kilobytes per second and researchers think faster versions are possible as the hardware improves.
Future designs could become directional or even guided in ways similar to fiber systems. I was intrigued by all this, so I spoke to Dr Nielsen about his work.
- Does the technology require line of sight and is it sensitive to temperature variations?
Yes it would require line of sight, no different to any other optical communication method using the visible, telecommunications or THz frequency spectrum. The usual pros and cons between optical communication methods and radio wave communication methods (WiFi included) apply.
But surprisingly, it’s not sensitive to temperature variations! That is, unless things get very cold (-100C kind of cold) as the negative luminescence effect actually grows stronger at higher temperatures, and this is currently the limiting factor for the magnitude of the effect.
You do not need to actively control the temperature of the emitter, in fact, the emitter should be left at ambient temperature so that it blends into its surroundings (no temp control required).
- Is it practical and what would an operational product look like?
It’s very early days. We only just demonstrated the effect for the first time, now the real engineering work begins.
It would be no different to a visible light LED, except this emits thermal radiation instead of visible light.
Yes, except using thermal radiation instead of visible light radiation. So if by lower frequencies you mean longer wavelengths, then yup!
The real difference is the ability to hide your communication from an outside observer. For example, when I open my laptop and go to connect to the internet, I can see all the available communication networks because I can detect their signal, even if I don’t know the password.
In this case, the very signal or act of communication is hidden if the observer doesn’t have the capability to look for it. No other communications methodology has this capability.
- But the same could be said for Lifi? The lower frequency means that the transfer rates will be much lower as well
Lower frequency of light does not immediately mean lower data transfer rates unless you are close to the limit (i.e. the fundamental limit for optical frequencies like Lifi is in the 100sTHz, but we don’t operate anywhere close to that).
If I was in a room with a Lifi, I can see the optical radiation, with a camera, a detector, etc.
The difference here is that this can be designed so the camera, detector, etc, never even sees the act of communication, even if I was in the same room as it.
You could never hide from a camera (i.e. outside observer), no matter how fast you modulate or what encryption you use. That optical radiation is being used for communication in the first place with Lifi, because you are always only using ON and OFFs to communicate (so the time average is still “bright”).
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