kbd-audio

Description

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

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. The tool is still in development, but you can see a short demonstration here:

Video: Keytap2 - recovering text from typing sound (7:50)

CTF: can you guess the text being typed?

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  
  

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

Linux and Mac OS

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

Windows

(todo, PRs welcome)

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
keytap	text	stable
keytap-gui	gui	stable
keytap2	text	development
keytap2-gui	gui	development
-	extra	-
guess_qp	text	experiment
guess_qp2	text	experiment
key_detector	text	experiment
scale	text	experiment
subreak	text	experiment
key_average_gui	gui	experiment

Tool details

• record-full

  Record audio to a raw binary file on disk

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

  ---

• play-full

  Playback a recording captured via the record-full tool

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

  ---

• record

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

  ./record output.kbd [-cN]
  

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• play

  Playback a recording created via the record tool

  ./play input.kbd [-pN]
  

  ---

• 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] [-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]
  

  **Live demo (WebAssembly threads required) **

  

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• keytap2-gui (work in progress)

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

  ./keytap2-gui recording.kbd n-gram.txt
  

  

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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
  

  

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• view-gui

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

  ./view-gui input.kbd
  

  

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Feedback

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