Published on August 22nd, 2011 | by Alexis Argent0
Password-based network security could be vulnerable
A successful man-in-the-middle attack on the smartphones of Def Con attendees in early August demonstrated that simple password-based security might not be sufficient to keep a determined, sophisticated attacker from listening in on data transmissions, according to a report from PhysOrg.
However, the publication stated, MIT researchers have published a paper outlining a new type of authentication system that can make Wi-Fi connections much harder to break into. Taking advantage of basic properties of Wi-Fi transmissions, the setup would authenticate a connection with a timing-based set of signals that would cause standard man-in-the-middle hijacking attempts to fail.
In an MITM attack, the attacker needs to drown out the signal from the legitimate sender. But the researchers’ new system ensures that any attempt to do so will be detected. The trick is that, after transmitting its encryption key, the legitimate sender transmits a second string of numbers related to the key by a known mathematical operation. But whereas the key is converted into a wireless signal in the ordinary way — it’s encoded as changes in the amplitude of a radio wave — the second string of numbers is encoded as alternating bursts of radiation and silences.
Through the silences of one, the receiver will hear the bursts of the other. The overlapping sequences will look to the receiver like a wholly new sequence, which won’t match up with the transmitted key, indicating an MITM attack.
Of course, the attacker could try to drown out the entirety of the legitimate transmission and then send his own key. But that would require broadcasting a signal of such long duration that it, too, would alert the receiver to an attack.
“Other people have been focusing on protecting against man-in-the-middle attacks and just assumed that an adversary would be able to tamper with messages,” says Tadayoshi Kohno, an assistant professor of computer science and engineering at the University of Washington. “These guys look under the hood and say, ‘Wait, if we actually know how wireless works, we can construct a system so that an adversary couldn’t tamper with messages to begin with.’ In a way, there was a fundamental assumption that all preceding work had, and this paper steps back and says that assumption is incorrect, and here’s why it’s incorrect, and here’s what we can do with it.”
The reports of an MITM attack on 4G phones are still being verified, and 4G itself is a vague term that encompasses many different technical approaches. But if the reports prove true, then cell phones, too, could benefit from the MIT researchers’ security scheme. “You could imagine that the same protocol could be used in cell phone networks as well,” Zeldovich says. “At the design level, the idea sounds like it should be applicable.”
“If an attacker tries to substitute his key for the legitimate sender’s, he’ll have to send the corresponding sequence of bursts and silences. But that sequence will differ from the legitimate one. Through the silences of one, the receiver will hear the bursts of the other. The overlapping sequences will look to the receiver like a wholly new sequence, which won’t match up with the transmitted key, indicating an MITM attack,” the publication explained.
Increasingly sophisticated hacking techniques can often be neutralized by equally sophisticated defense measures, but non-technical attacks – including social engineering – require a degree of organizational familiarity with potentially fraudulent requests for information.
Physorg, Via Airtight Networks
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