Just when we were getting used to 5G
Rice University and Brown University
Crafty hackers can make a tool to eavesdrop on some 6G wireless signals in as little as 5 minutes using office paper, an inkjet printer, a metallic foil transfer and a laminator.
The wireless security hack was discovered by engineering
researchers from Rice University and Brown University, who will present their
findings and demonstrate the attack this week in San Antonio
at ACM WiSec 2022, the
Association for Computing Machinery’s annual conference on security and privacy
in wireless and mobile networks.
“Awareness of a future threat is the first step to counter that
threat,” said study co-author Edward Knightly,
a professor of electrical and computer engineering at Rice. “The frequencies
that are vulnerable to this attack aren’t in use yet, but they are coming and
we need to be prepared.”
In the study, Knightly, Brown engineering professor Daniel Mittleman and
colleagues showed that an attacker could easily make a sheet of office paper
covered with 2D foil symbols — a metasurface — and use it to redirect part of a
150 gigahertz “pencil beam” transmission between two users.
They dubbed the attack “ Metasurface-in-the-Middle” as a nod to both the hacker’s tool and the way it is wielded. Metasurfaces are thin sheets of material with patterned designs that manipulate light or electromagnetic waves. “Man-in-the-middle” is a computer security industry classification for attacks in which an adversary secretly inserts themself between two parties.
The 150 gigahertz frequency is higher than is used in today’s 5G
cellular or Wi-Fi networks. But Knightly said wireless carriers are looking to
roll out 150 gigahertz and similar frequencies known as terahertz waves or
millimeter waves over the next decade.
“Next-generation wireless will use high frequencies and pencil
beams to support wide-band applications like virtual reality and autonomous
vehicles,” said Knightly, who will present the research with co-author Zhambyl
Shaikhanov, a graduate student in his lab.
In the study, the researchers use the names Alice and Bob to
refer to the two people whose communications are hacked. The eavesdropper is
called Eve.
To mount the attack, Eve first designs a metasurface that will
diffract a portion of the tight-beam signal to her location. For the
demonstration, the researchers designed a pattern with hundreds of rows of
split rings. Each looks like the letter C, but they are not identical. The open
part of each ring varies in size and orientation.
“Those openings and orientations are very specifically done to
get the signal to diffract in the exact direction Eve wants,” Shaikhanov said.
“After she designs the metasurface, she prints it on a regular laser printer,
and then she uses a hot stamping technique that's used in crafting. She places
a metal foil on the printed paper, feeds it through a laminator and the heat
and pressure create a bond between the metal and the toner.”
Mittleman and study co-author Hichem Guerboukha, a
postdoctoral research fellow at Brown, showed in a 2021 study that
the hot-stamping method could be used to make split-ring metasurfaces with
resonances up to 550 GHz.
“We developed this approach in order to lower the barrier for
fabrication of metasurfaces, so that researchers could test many different
designs quickly and inexpensively,” Mittleman said. “Of course, this lowers the
barrier for eavesdroppers too.”
Scholars from Rice and Brown say that next-generation wireless
networks that use the technology could be designed with built-in defenses
against the ‘metasurface-in-the-middle’ attack. Video courtesy Rice University.
The researchers said they hope the study will dispel a common
misperception in the wireless industry that higher frequencies are inherently
secure.
“People have been quoted saying millimeter-wave frequencies are
‘covert’ and ‘highly confidential’ and that they ‘provide security,’”
Shaikhanov said. “The thinking is, ‘If you have a super narrow beam, nobody can
eavesdrop on the signal because they would have to physically get between the
transmitter and the receiver.’ What we’ve shown is that Eve doesn’t have to be
obtrusive to mount this attack.”
The research showed the attack would be difficult for Alice or
Bob to detect today. And while the metasurface must be placed between Alice and
Bob, “it could be hidden in the environment,” Knightly said. “You could conceal
it with other sheets of paper, for instance.”
Knightly said now that wireless researchers and equipment
manufacturers know about the attack, they can further study it, develop
detection systems and build those into terahertz networks up front.
“If we had known from day one, when the internet first came out,
that there would be denial-of-service attacks and attempts to take down web
servers, we would have designed it differently,” Knightly said. “If you build
first, wait for attacks and then try to repair, that is a much more costly and expensive
path than designing securely up front.
“Millimeter-wave frequencies and metasurfaces are new
technologies that can each be used to advance communication, but any time we
get a new capability for communication we have to ask the question, ‘What if the
adversary has this technology? What new capabilities will it give them that
they didn’t have in the past? And how can we realize a secure network against a
strong adversary?”
Fahid Hassan of Rice is a study co-author.
This
research was supported by Cisco, Intel, the National Science Foundation
(1955075, 1923782, 1824529, 1801857, 1923733, 1954780) and the U.S. Army
Research Laboratory (W911NF- 19-2-0269).
This story was authored by Jade Boyd, science editor and
associate director of news and media relations in Rice University’s Office of
Public Affairs.
