Experiment Shows How to Eavesdrop on Terahertz Frequencies

  • October 19, 2018
    Two black stands with an antenna and receiver are positioned to face each other in an open room.
    Photo: Mittleman Group/Brown University
    In a series of experiments, researchers at Brown University showed that it’s possible to use a metal plate to divert part of a wireless signal broadcast in the terahertz range.


    Society is poised to enjoy a major communications upgrade with the widespread launch of commercial 5G networks. Meanwhile, a handful of researchers have already started to think ahead to 6G—the next (next) generation of wireless and cellular technology.

    Just as 5G networks will transmit data on higher frequencies than previous generations, preliminary research suggests that the trend may well continue with 6G networks. Harnessing these waves brings a wealth of benefits. Along with offering more bandwidth for data transfers, higher-frequency wavelengths are expected to be more difficult to intercept—and lead to more secure communications.

    Today’s wireless networks rely on low-frequency, omnidirectional waves; these wide-area signals can easily be picked up by a third party using a transceiver without much concern for where the transceiver is placed. 5G networks will add narrower, higher-frequency millimeter waves, which technically span from about 30 gigahertz to 300 GHz, though frequencies between 25 GHz and 35 GHz have proven most popular with carriers. 6G networks could rely on even higher frequencies and narrower beams, possibly in the terahertz range.

    In theory, narrower beams that are highly directional could make it much more difficult for any eavesdroppers to access the broadcast. This is partly because if an eavesdropper placed a bulky transceiver in the path of a narrow terahertz broadcast, it would block the signal enough to alert the two communicating parties to the interception.

    But no method of wireless transmission is entirely secure, and the same is true for terahertz frequencies. Researchers have now demonstrated, in a study published in Nature, how someone could intercept and eavesdrop on a private conversation broadcast with terahertz waves (terahertz includes frequencies of 0.1 terahertz—100 GHz—and higher).


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