Something about audio CAPTCHAs Elie Bursztein, Romain Bauxis, - - PowerPoint PPT Presentation

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Something about audio CAPTCHAs Elie Bursztein, Romain Bauxis, - - PowerPoint PPT Presentation

Mar 31, 2023 270 likes •731 views

Something about audio CAPTCHAs Elie Bursztein, Romain Bauxis, Daniele Perito, Hristo Paskov, Celine Fabry, John Mitchell 1 Elie Bursztein (@elie) http://ly.tl/p18 The Failure of Noise-Based Non-Continuous Audio Captchas Elie Bursztein

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Something about audio CAPTCHAs

Elie Bursztein, Romain Bauxis, Daniele Perito, Hristo Paskov, Celine Fabry, John Mitchell

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

CAPTCHAS

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

CAPTCHAS

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

CAPTCHAS

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

CAPTCHAS

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

CAPTCHAS

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

CAPTCHAS

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

CAPTCHAS

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Audio capchas

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Audio capchas

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Outline

  • Audio captchas background
  • Breaking audio captchas
  • Evaluation results
  • Demo
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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Super secure captcha Captcha Maker

Creating audio captcha

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Super secure captcha Captcha Maker

Creating audio captcha

Voices

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Super secure captcha Captcha Maker

Creating audio captcha

Noises

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Super secure captcha

Creating audio captcha

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Type of noise

  • Additive noise i.e white noise
  • Convolutive noise i.e echo
  • Semantic noise i.e music
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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Noise intensity (RMS/SNR)

2 9 Microsoft J Digg A K Authorize K J 5 H

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Sound representation

WAV DFT Cep TFR TCR TDC

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Breaking audio captchas

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Solving an audio captcha

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Solving an audio captcha

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Solving an audio captcha

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Solving an audio captcha

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Solving an audio captcha

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Solving an audio captcha

C

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Solving an audio captcha

C T T A R A F R S 2

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Dealing with random noise

  • Statistical learning
  • Supervised learning
  • RLS (Regularized

least square) classifier

Authorize eBay Recaptcha Authorize Digg

5: J:

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Solver efficiency

Solver accuracy = Coverage * Precision^length Coverage: Segmentation Precision: Recognition rate

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Decaptcha

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Decaptcha overview

Web Site

Captcha scraping

Sound processing Mechanical Turk users

Captcha labels Discretized and segmented captcha

Classifier

Answers

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Testing corpus

Familly Name Description Constant Noise White White Gaussian noise. buzz Sine waves at 700 Hz, 2100 Hz and 3500 Hz. Regular noise pow 10 ms bursts of white Gaussian noise repeated every 100 ms. rnoise Every 100 ms, a section

  • f the signal is replaced

by white noise of the same RMS amplitude. lofi Add distortion, cracks, bandwidth limiting and

  • compression. Simulates
  • ld audio equipment.

echo The signal starts to echo at 0.6, 1.32, and 1.92 seconds. disintegrator Amplifies random half- cycles of the signal by a multiplier. Simulates a bad audio channel. Semantic noise chopin Chopin Polonaise for Piano No. 6, Op. 53. gregorian Gregorian chant. nina “Just in time“ by Nina Simone. Table III

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Synthetic evaluation

−5 5 10 15 20 10 20 30 40 50 60 70 80 90 100 SNR (dB) Per−Captcha Precision (%) white buzz gregorian nina chopin pow echo, lofi, rnoise, disintegrator

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Semantic noise

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Captcha features

Scheme Authorize Digg eBay Microsoft Recaptcha Yahoo Length 5 5 6 10 8 7 Type of voice Female Female Various Various Various Child Background Noise None Constant (random) Constant (random) Constant (random) Constant (random) None Intermediate noise None None Regular (speech) Regular (speech) Regular (speech) Regular (speech) Charset 0-9a-z a-z 0-9 0-9 0-9 0-9

  • Avg. duration

5.0 6.8 4.4 7.1 25.3 18.0 Sample rate 8000 8000 8000 8000 8000 8000 22050 Beep no no no no no yes

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Results

Length Coverage Digit Captcha Authorize 5 100 97 89.2% Digg 5 100 76 41.4% eBay 6 85.6 92.5 82.9% Microsoft 10 80.6 89.6 48.9% Recaptcha 8 99.9 40.5 1.5% Yahoo 7 99.1 74.7 45.4%

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Recaptcha semantic noise

  • 70
  • 60
  • 50
  • 40
  • 30
  • 20
  • 10

20 40 60 80 100 120 140 160 180 200

3 7 N 2 1 4 9 N 5 DB Time in seconds

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Recaptcha semantic noise

  • 70
  • 60
  • 50
  • 40
  • 30
  • 20
  • 10

20 40 60 80 100 120 140 160 180 200

3 7 N 2 1 4 9 N 5 DB Time in seconds

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Confusion matrices

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

How many captchas do you need ?

10

2

10

3

10

4

10 20 30 40 50 60 70 80 90 100 Per−Captcha Precision (%) Corpus Size (in Digits) Authorize Digg Ebay MSLive Recaptcha Yahoo

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Conclusion

  • Non-continuous based captchas are broken
  • Urgent need to come-up with the next generation of

audio captchas

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Elie Bursztein (@elie) The Failure of Noise-Based Non-Continuous Audio Captchas http://ly.tl/p18

Questions ?

Thanks http://ly.tl/p18

Twitter: @elie