Naren Anand is worried about your Wi-Fi, and he’s working on a way to make it safer.
“When it comes to Wi-Fi security,” says the computer engineering Ph.D. student at Rice University, “we depend on passwords and encryption methods to keep our information safe. But hackers can always come up with a new way of breaking encryption.”
Anand, a member of the Rice Networks Group, is working a new kind of security. Specifically, he wants to make sure that the wireless network signal reaches you, the intended user, while dodging the prying eyes of Internet eavesdroppers intent on stealing sensitive information online.
With the publication of a new paper at the IEEE Conference in March 2012, Anand, with the support of his advisor, Electrical and Computer Engineering Professor Edward Knightly, and in collaboration with HP Labs, will announce a novel approach to wireless network security that could do just that, while changing the way that we think about keeping our Wi-Fi signals safe from intruders. The technique is called STROBE, which stands for Simultaneous TRansmission with Orthogonally Blinded Eavesdroppers.
Currently, a wireless network signal like the Wi-Fi at a local coffee shop is broadcast equally to everyone in a given area. While the coffee-sipping web surfers who are meant to freely and harmlessly use the signal can protect their sensitive data with passwords and encryption techniques, malicious eavesdroppers can intercept vulnerable data, download it, and crack through layers of protective codes long after closing time.
STROBE, however, capitalizes on leading edge antenna technology in order to strengthen Wi-Fi security by blocking out, or “blinding,” all but the intended recipient of a Wi-Fi signal. The forthcoming paper is a new study of STROBE and its effectiveness.
STROBE works by changing the way a signal is sent from the wireless access point, so that the intended receiver of a signal is also the only receiver of that signal. Anybody else who tries to “sniff” packets of data being transmitted over the air will find only meaningless interference, which is created through the use of multi-user beamforming, and with the power of multiple wireless antennas.
Whereas current wireless antennas alternately transmit to a single user at a time, multi-user beamforming uses multiple antennas to send out an array of signals that simultaneously serve multiple users. These multiple antennas divide up the bandwidth load, helping to increase network speeds.
In working with multi-user beamforming, Anand soon realized that speed was not its only application. He could also send out different kinds of signals. Some of those signals could even be used to cause confusion and frustration for potential hackers while efficiently serving the intended user. STROBE sends out one perfectly good signal to the user of choice, and it uses the wireless access point’s other antennas to unleash a salvo of interference everywhere else, which he calls “garbage.”
“Eavesdroppers can’t hear the packet, period,” Anand says of the Wi-Fi security technique.“STROBE prevents non-intended users from eavesdropping and trying to process offline what someone has said. The bad guy can’t even get to that point.”
While many have touted the benefits of multiple antenna technology—whose capabilities will expand with the implementation of forthcoming 802.11ac standards for wireless networks—for increased wireless bandwidth, Anand and Knightly focused their research and testing on the security ramifications of multiple signals.
Anand began by blocking out unwanted intruders in a limited space, about the size of an office in Rice’s Duncan Hall. After successfully thwarting network threats in that limited area, he and Knightly soon realized the potential for STROBE to expand far beyond a few bookcases.
“We were trying to figure out ways to wall off different spatial regions,” Knightly said. “The eureka moment was when Naren realized you could just wall off everybody.”
To simulate a real-world environment during testing, Anand had a team of eavesdroppers attempt crack his wireless network.
“We stood around a conference table at Duncan Hall,” says Anand, “I had a transmitter and four antennas, a scenario that is completely likely in a consumer access situation, and I put an intended user in one spot and had three eavesdroppers in a circle around the transmitter, trying to access the signal. Then I had them move in closer and closer.
“The idea is that if you are trying to overhear, it would be easier to eavesdrop the closer you got to a conversation. But with STROBE, even when the antennas are put incredibly close together—just a few centimeters apart—I was able to transmit data to the intended user while blinding the other malicious users.”
While the consumer applications for STROBE technology remain to be seen, Knightly envisions a bright future for the approach, especially in light of the new 802.11ac wireless standards.
“The basic principle is to exploit physical layer resources to enhance security,” Knightly said. “This can open doors to new and more powerful methods to thwart wireless attackers. In terms of both security and the use of multiple antennas, STROBE is a paradigm shift.”