Unpacking 6G Security Challenges—The Metasurface-in-the-Middle Attack

June 03, 2022 by Jake Hertz

Since 6G technology is still in its early days, there's a lot to be learned. Increasing the world's 6G knowledge, Rice University discovered an attack that creates a vulnerability in 6G frequency bands.

While it feels like 5G technology has just reached the market, folks in the industry already have their sights set on 6G. The next generation in cellular communications, 6G is still many years away from practical use in any commercial applications, but that hasn't stopped it from being the subject of intense research and development efforts in the past couple of years.


Overview of possible spectrum for mobile systems.

Overview of possible spectrum for mobile systems. Image used courtesy of 6G Flagship


Recently, researchers from Rice University made headlines when they announced the discovery of a new man-in-the-middle attack that renders certain 6G frequencies vulnerable to security exploits. 

In this article, we'll discuss the discovered attack, how it works, and the potential impact the finding can have on the future of 6G technology.


6G Means Higher Frequency 

In evolving from 5G technology to 6G technology, one of the biggest changes expected to occur is the transition to higher frequency bands.

While much of the new communication standard is not defined yet, many are expecting that 6G frequencies will range from 90 GHz all the way up to 3 THz. Compared to 5G communications, which exist from about 3.3 GHz to 4.2 GHz, the 6G frequencies should offer significantly higher data rates.


6G will use higher frequencies than any previous technology generation.

6G will use higher frequencies than any previous technology generation. Image used courtesy of ICNIRP and Mi-Wave


However, along with these higher frequencies comes greater attenuation of the electromagnetic (EM) wave as it propagates through its given medium. Thus, the challenge here becomes how to sustain a flexible and reliable network that is simultaneously capable of supporting a massive number of users in spite of this high attenuation.


6G Directionality and Security

To address these challenges, many suggest the need for 6G networks to leverage high-gain, highly-directional antennas with strict beam alignment. By using narrow beamwidths with a point-to-point communication scheme, researchers expect to compensate for the extremely high path loss associated with the higher frequencies of 6G.

As an added benefit, researchers are also touting that, by using highly directional antennas, 6G should theoretically be more secure than wireless communications with higher beamwidths. The theory is that by narrowly directing communications between receiver and transmitter, there is less chance of an eavesdropper gaining access to a communication channel.

This purported security benefit is a big concern, as 6G technology is expected to empower more interconnected personal devices than ever before—leading to more sensitive, personal information being transmitted than in the past.


Metasurface-in-the-Middle Attack

Hoping to check that 6G is secure as technology is being developed, researchers from Rice University, in a recent paper, revealed a man-in-the-middle attack directed at 6G frequencies that show legitimate security concerns.

The researchers describe their attack as a metasurface-in-the-middle attack (MSITM), where an adversary can use a carefully designed metasurface to intercept communications at 6G frequencies. 

In the attack, an adversary can redirect a portion of the sensitive communications by designing a metasurface and placing it directly in the line of sight between transmitter and receiver. 


Diagram of the metasurface-in-the-middle-attack.

Diagram of the metasurface-in-the-middle-attack. Image used courtesy of Shaikhanov et al


Notably, the researchers showed that the metasurface does not need to be complicated but can be produced through DIY methods using:

  • Office paper
  • An inkjet printer
  • A metallic foil transfer
  • A laminator 

The design that they demonstrate can induce a phase discontinuity at the surface interface, allowing for controllable diffraction radiation patterns that then establish a diffraction-based eavesdropping channel for the adversary. 

The ultimate fear, in practice, is that an adversary can use this technique by attaching a metasurface to a drone to intercept conversations regardless of the location of the transmitter and receiver.


Paving the Way for 6G

While 6G technology may be quite a ways away, it is undoubtedly crucial that researchers start investing time and energy into the field today. By finding potential security vulnerabilities in the technology, the researchers from Rice University are ensuring a safer future for the technology, where designers can address these exploits and build countermeasures into the technology. 

All in all, we're sure to see more 6G research and technology trickling in over the next foreseeable future.