Phone Gyroscope Signals Can Eavesdrop On Your Conversations

A gyroscope is a device made for measuring orientation and can typically be found in modern smartphones or tablet PCs to enable rich user experience. A team from Stanford managed to recognize simple words from only analyzing gyroscope signals (PDF warning). The complex inner workings of MEMS based gyroscopes (which use the Coriolis effect) and Android software limitations only allowed the team to only sniff frequencies under 200Hz. This may therefore explain the average 12% word recognition rate that was achieved with custom recognition algorithms. It may however still be enough to make you reconsider installing an app that don’t necessarily need access to the on-board sensors to work. Interestingly, the paper also states that STMicroelectronics currently have a 80% market share for smartphone / Tablet PCs gyroscopes.

On the same topic, you may be interested to check out a gyroscope-based smartphone keylogging attack we featured a couple of years ago.

9 thoughts on “Phone Gyroscope Signals Can Eavesdrop On Your Conversations

  1. very good paper, interesting read.

    STM might be the biggest player in the smartphone market, but i bet InvenSense is preferred for stabilization and IMU applications in multirotors and RC helicopters and the like.

    Also i wouldn’t worry about eavesdropping using this attack, since the team used a setup of subwoofers blasting out signals < 200 Hz at 75dB (to get a good SNR).
    And the STM chip only supports samplerates up to 800 Hz.

    1. The InvenSense MPU-6000 does support a samplerate of up to 8 kHz, the same bandwidth of a POTS line, or most telephone conversations. Combined with high resolution samples (16 bits) this can result in pretty good dynamic range too.

      However, i doubt the android or ios API will let you sample it at those rates, and if you need to break in to kernel space, you might as well just use the microphone.

      Ok, I looked it up, and the android api supports update rates of max. 200 Hz

  2. “A gyroscope is a device made for measuring orientation and can typically be found in modern smartphones or tablet PCs…”
    Nope, these “gyro” are rate sensors, they can only sense the rate at which the orientation changes, not the orientation itself.

    1. no, they contain both. We have Gyros which respond quickly, but drift over time, and we have accelerometers which respond slowly but are accurate over time. We can merge these two sensor readings to give use a quick response which is also accurate

  3. It’s clever, but realistically dozens of organization have access to your cell phone’s microphone, so this is rather pointless for spying on people really since it is already doe the easy way.

    1. I have old nokia (s60 family) as primary phone, I have android phone with cyanogenmod flashed as an internet device – what organisations can have access to my phones microphone?

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