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reCAPTCHA-mobile is an implementation of reCAPTCHA agent verification for mobile browsers. It works by using accelerometer data from mobile phones which are accessible through Javascript.

Server Code

We wrote two servers in implementing this project.

  • data-capture/*: Contains the code for the web-server we wrote to get experimental data from our phones. We hosted two pages from this server on heroku, which are accessibly at (1) and (2)
    1. The first of these was used to collect data from users. When users click the button in the page, we get 5 seconds of motion data from their phone's accelerometer.
    2. The second of these was used for us to collect annotated data. We type a text label, and then can repeatedly send samples from our phone while we perform an activity that corresponds to that label, such as walking, sitting, being in a car, etc.
  • captcha-server/*: Contains the code for the web-server we wrote for the central CAPTCHA server described in detail in section 4 of the paper. The captcha-server/ file contains all of the server-side code. The captcha-server/templates/register.html page contains the client side code for displaying client key registrations to users and allowing users to manage keys.

Data Collection and Storage

To actually collect the data, we used deployed the server in data-capture/* on heroku. The server sent data to Then, we wrote a quick script, which you can find in gmail/* to download the data from that gmail account, clean it up, load it into an appropriate format, and save it to a file.

Model Training

  • This is the central training file. This file loads a particular dataset from disk, trains a configured recurrent neural network model with it, and saves the model along with the associated training and testing files to disk.
  • Contains various utility functions used in the testing and training process.
  • loaded.ipynb: This is an iPython Notebook that we used to test the trained models with a test set.
  • ckpt/*: Contains the trained models
  • npy/*: Contains the training and test files that are emitted for a particular model


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