Variations in the intensity of each pixel create fluctuations in the sound created by the screen's power supply, leaking information about the image being refreshed-information that can be processed with machine learning algorithms to extract details about what's being displayed. Advertisementīecause of the way computer screens render a display-sending signals to each pixel of each line with varying intensity levels for each sub-pixel-the power sent to each pixel fluctuates as the monitor goes through its refresh scans. Even though LCD screens consume a lot less power than the old CRT beasts, they still generate the same sort of noise, though in a totally different frequency range. And acoustic bugging has also been shown to reveal keystrokes on a physical keyboard.Īnyone who remembers working with cathode ray tube monitors is familiar with the phenomenon of coil whine. In former MI5 Assistant Director Peter Wright's book Spycatcher, Wright recounted how British intelligence used a phone tap to record audio from an Egyptian embassy's cipher machine during the Suez Crisis. And nation-state use of acoustic side-channels has been documented, though not against computer screens. Genkin and Tromer-with another team of researchers, including Adi Shamir, one of the co-inventors of the RSA cryptographic algorithm-previously demonstrated a way to use noise generated by a computer's power supply and other components to recover RSA encryption keys. This isn't the first acoustic side-channel attack ever discovered, by any means. While Van Eck phreaking uses radio signal emissions that leak from display connectors, the Synesthesia research leverages "coil whine," the audio emissions from transformers and other electronic components powering a device's LCD display. The research, supported by the Check Point Institute for Information Security at Tel Aviv University (of which Schuster and Tromer are members) and funded in part by the Defense Advanced Research Projects Agency, examined what amounts to an acoustic form of Van Eck phreaking. All you'll need to do is process the audio picked up by their microphones.ĭaniel Genkin of the University of Michigan, Mihir Pattani of the University of Pennsylvania, Roei Schuster of Cornell Tech and Tel Aviv University, and Eran Tromer of Tel Aviv University and Columbia University investigated a potential new avenue of remote surveillance that they have dubbed " Synesthesia": a side-channel attack that can reveal the contents of a remote screen, providing access to potentially sensitive information based solely on "content-dependent acoustic leakage from LCD screens."
Ken Fisher / Getty Images reader comments 65 withĮver wonder what the people on the other end of a Hangouts session are really looking at on their screens? With a little help from machine learning, you might be able to take a peek over their shoulders, based on research published at the CRYPTO 2018 conference in Santa Barbara last week.
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