Wireless security method shapes signals to foil eavesdroppers

Wireless security method shapes signals to foil eavesdroppers

Technology News |
By Rich Pell

Encryption methods now used to secure communications from eavesdroppers can be challenging to scale toward emerging high-speed and ultra-low-latency systems such as 5G and beyond. The very nature of encryption, say the researchers, requires exchange of information between sender and receiver to encrypt and decrypt a message, which makes the link vulnerable to attacks and also requires computing that increases latency.

For networks that support latency-critical systems such as self-driving cars, robots and other cyber-physical systems, minimizing time to action is critical. To address this security gap, the researchers developed a methodology that incorporates security in the physical nature of the signal.

To do so, the researchers developed a new millimeter-wave wireless microchip that allows secure wireless transmissions to prevent interception without reducing latency, efficiency and speed of the 5G network. The technique, say the researchers, should make it very challenging to eavesdrop on such high-frequency wireless transmissions, even with multiple colluding bad actors.

“We are in a new era of wireless — the networks of the future are going to be increasingly complex while serving a large set of different applications that demand very different features,” says senior researcher Kaushik Sengupta. “Think low-power smart sensors in your home or in an industry, high-bandwidth augmented reality or virtual reality, and self-driving cars. To serve this and serve this well, we need to think about security holistically and at every level.”

Instead of relying on encryption, the rsearchers’ method shapes the transmission itself to foil would-be eavesdroppers. To explain this, say the researchers, it helps to picture wireless transmissions as they emerge from an array of antennas: With a single antenna, radio waves radiate from the antenna in a wave; when there are multiple antennas working as an array, these waves interfere with each other like waves of water in a pond. The interference increases the size of some wave crests and troughs and smooths out others.

An array of antennas is able to use this interference to direct a transmission along a defined path. But besides the main transmission, there are secondary paths. These secondary paths are weaker than the main transmission, but in a typical system they contain the exact same signal as the main path. By tapping these paths, potential eavesdroppers can compromise the transmission, say the researchers.

They realized they could foil eavesdroppers by making the signal at the eavesdroppers’ location appear almost as noise by chopping up the message randomly and assigning different parts of the message to subsets of antennas in the array. The researchers were able to coordinate the transmission so that only a receiver in the intended direction would be able to assemble the signal in the correct order. Everywhere else, the chopped-up signals arrive in a manner that appear noise-like.

“Imagine in a concert hall, while playing Beethoven’s symphony No. 9, every instrument, instead of playing all the notes of the piece, decides to play randomly selected notes,” says Sengupta. “They play these notes at correct times, and remain silent between them, such that each note in the original piece gets played by at least some instrument. As the sound waves carrying these notes from all the instruments travel through the hall, at a certain location, they can be made to arrive precisely in the correct fashion. The listener sitting there would enjoy the original piece as if nothing has changed. Everyone else would hear a cacophony of missing notes arriving at random times, almost like noise. This is, in principle, the secret sauce behind the transmission security — enabled by precise spatial and temporal modulation of these high-frequency electromagnetic fields.”

If an eavesdropper tries to intercept the message by interfering with the main transmission, it would cause problems in the transmission and be detectable by the intended user. Although it is theoretically possible that multiple eavesdroppers could work together to collect the noise-like signals and attempt to reassemble them into a coherent transmission, says Sengupta, the number of receivers needed to do that would be “extraordinarily large.”

“We showed for the first time that it is possible to stitch several noise-like signatures into the original signal by colluding eavesdroppers applying AI, but it is very challenging,” says Sengupta. “And we also showed techniques by which the transmitter can fool them. It is a cat-and-mouse game.”

The researchers created the entire end-to-end system in a silicon chip that is manufactured by standard silicon foundry processing. It would be possible to use encryption along with the new system for additional security, say the researchers.

“You can still encrypt on top of it but you can reduce the burden on encryption with an additional layer of security,” says Sengupta. “It is a complementary approach.”

For more, see “Secure space–time-modulated millimetre-wave wireless links that are resilient to distributed eavesdropper attacks.”

Related articles:
‘Funtenna’ hack turns IoT devices into radios
Microsoft finds security vulnerabilities in IoT, OT devices
First quantum-resistant network encryption solution launched
Quantum sensor uses atoms to receive common communications signals


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