kbd-audio

This is a collection of command-line and GUI tools for capturing and analyzing audio data.

Keytap

The most interesting tool is called keytap - it can guess pressed keyboard keys only by analyzing the audio captured from the computer’s microphone.

Check this blog post for more details:

Keytap: description and some random thoughts

Video: short demo of Keytap in action

Try it online:

Keytap2

The keytap2 tool is another interesting tool for recovering text from audio. It does not require training data - instead it uses statistical information about the frequencies of the letters and n-grams in the English language.

A more detailed description of the tool is available here: Keytap2 discussion

Video: short demo of Keytap2 in action

CTF: can you guess the text being typed?

Try it online:

Keytap3

This version introduces significant algorithm improvements and better n-gram statistics compared to keytap2. The attack is now fully
automated and does not require any manual intervation during the text recovery process.

Video: short demo of using Keytap3

Video: another example of using Keytap3

GUI for Keytap3

Check if your keyboard is vulnerable to Keytap:

What people say about Keytap

“This works incredibly well.
I hope you realize what you’ve created (and made available to every person in the world).” – ffpip

“I just tried it and it works incredibly well. It kind of makes me want to stop using a mechanical keyboard.” – Karawebnetwork

“This attack and Van Eck phreaking are why Edward Snowden, while typing passwords and other sensitive information, would pull a blanket over himself and his laptop.” – aarchi

“This is what mechanical keyboard users deserve” – super guy

“fuck…” – Lluis Franco

Build instructions

Dependencies:

• SDL2 - used to capture audio and to open GUI windows libsdl

  [Ubuntu]
  $ sudo apt install libsdl2-dev
  
  [Mac OS with brew]
  $ brew install sdl2
  
  [MSYS2]
  $ pacman -S git cmake make mingw-w64-x86_64-dlfcn mingw-w64-x86_64-gcc mingw-w64-x86_64-SDL2
  

• FFTW3 (optional) - some of the helper tools perform Fourier transformations fftw

Linux, FreeBSD, Mac OS, Windows (MSYS2 + MinGW)

git clone https://github.com/ggerganov/kbd-audio
cd kbd-audio
git submodule update --init
mkdir build && cd build
cmake ..
make

Tools

Short summary of the available tools. If the status of the tool is not stable, expect problems and non-optimal results.

Name	Type	Status
record	text	stable
record-full	text	stable
play	text	stable
play-full	text	stable
view-gui	gui	stable
view-full-gui	gui	stable
key-detector	text	stable
keytap	text	stable
keytap-gui	gui	stable
keytap2-gui	gui	stable
keytap3	text	stable
keytap3-gui	gui	stable
-	extra	-
guess-qp	text	experiment
guess-qp2	text	experiment
keytap3-multi	text	experiment
scale	text	experiment
subreak	text	experiment
key-average-gui	gui	experiment
keytap2	text	experiment

Tool details

• record-full

  Record audio to a raw binary file on disk

  ./record-full output.kbd [-cN]
  

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• play-full

  Playback a recording captured via the record-full tool

  ./play-full input.kbd [-pN]
  

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• record

  Record audio only while typing. Useful for collecting training data for keytap

  ./record output.kbd [-cN] [-CN]
  

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• play

  Playback a recording created via the record tool

  ./play input.kbd [-pN]
  

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• keytap

  Detect pressed keys via microphone audio capture in real-time. Uses training data captured via the record tool.

  ./keytap input0.kbd [input1.kbd] [input2.kbd] ... [-cN] [-CN] [-pF] [-tF]
  

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• keytap-gui

  Detect pressed keys via microphone audio capture in real-time. Uses training data captured via the record tool. GUI version.

  ./keytap-gui input0.kbd [input1.kbd] [input2.kbd] ... [-cN] [-CN]
  

  Online demo: https://keytap.ggerganov.com

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• keytap2-gui record.kbd n-gram-dir [-pN] [-cN] [-CN]

  Detect pressed keys via microphone audio capture. Uses statistical information (n-gram frequencies) about the language. No training data is required. The ‘record.kbd’ input file has to be generated via the record-full tool and contains the audio data that will be analyzed. The ‘n-gram-dir’ folder file has to contain n-gram probability files for the corresponding language.

  ./keytap2-gui record.kbd ../data
  

  Online demo: https://keytap2.ggerganov.com

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• keytap3

  Fully automated recovery of unknown text from audio recordings.

  ./keytap3 input.kbd ../data [-cN] [-CN] [-pF] [-tF] [-FN] [-fN]
  

  Online demo: https://keytap3.ggerganov.com

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• keytap3-gui

  GUI version of the keytap3 tool.

  ./keytap3-gui input.kbd ../data [-cN] [-CN] [-pF] [-tF] [-FN] [-fN]
  

  Online demo: https://keytap3-gui.ggerganov.com

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• view-full-gui

  Visualize waveforms recorded with the record-full tool. Can also playback the audio data.

  ./view-full-gui input.kbd [-pN]
  

  

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• view-gui

  Visualize training data recorded with the record tool. Can also playback the audio data.

  ./view-gui input.kbd [-pN]
  

  

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Feedback

Any feedback about the performance of the tools is highly appreciated. Please drop a comment here.