Researchers from Brown University suggested that terahertz data links are not as immune to eavesdropping as assumed in previous studies
Terahertz radiation can carry up to 100 times more data than conventional microwaves used in wireless communication, owing to its higher frequency. This radiation has enhanced bandwidth that enables its use to enhance cyber security. Microwaves propagate in wide-angle broadcasts, whereas terahertz waves propagate in narrow and very directional beams. In microwave communications, an eavesdropper can install an antenna anywhere in the broadcast cone. This will allow to pick up the signal without interfering with the intended receiver. However, an eavesdropper requires to place the antenna between the transmitter and receiver in terahertz networks, owing to its narrow beams.
A team of researchers from Brown, Rice University, and the University at Buffalo set up a direct line-of-site terahertz data link between a transmitter and receiver and experimented with devices capable of intercepting signal. The team was able to demonstrate several strategies capable of stealing signal without being detected. Moreover, these strategies were possible even when the data-carrying beam is very directional. In one such strategy, the team placed objects at the very edge of a beam, which is capable of scattering a tiny portion of the beam. A reliable data link requires the diameter of the beam to be slightly larger than the aperture of the receiver. This in turn enables an attacker to work with without casting a detectable shadow on the receiver.
The tem demonstrated that a flat piece of metal could redirect a portion of the beam to a secondary receiver, which is operated by an attacker. The team was able to acquire a usable signal at the second receiver with no significant loss of power at the primary receiver. Moreover, the team used a metal cylinder in the beam instead of a flat plate to show an even more flexible approach from the attacker’s perspective. The researchers also demonstrated another type of attack, which involved a lossless beam splitter that can be challenging to detect. The beam splitter placed in front of a transmitter can enable to steal data without setting off alarm among network administrators. The research was published in Nature on October 15, 2018.