Story of reCAPTCHA : A Session By Naga Chokkanathan @ CRMIT (http://www.crmit.com/) Video Recording Of This Session : http://youtu.be/K5XI60uc06c

1. Story of reCAPTCHA
Naga Chokkanathan

2. Remember This?
• CAPTCHA
– Completely
– Automated
– Public
– Turing test to tell
– Computers and
– Humans
– Apart
• Security for the website, Agreed
• But for the real users?
• BORING task
• Waste of time
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

3. CAPTCHA
• Yahoo! popularized it first
• Later, almost every website started using CAPTCHA to
avoid automated attacks
• Very effective : Only people can crack those word /
image puzzles
• But, it is a waste of time too
– Assuming you spend 10 seconds on a CAPTCHA
– Multiplied by 200 Million CAPTCHAs every day
– Thousands of hours being wasted on a daily basis
• Can something be done about this? (1)
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

4. Another Problem
• Digitizing Books
• Process:
– Stage 1
• Scan
• Convert to image
• Save
– Stage 2
• Use OCR to convert
images to text
• Searchable Text
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

5. OCR
• Optical Character Recognition
• Wonderful technology
• But not always reliable
• Especially with old text (due to ancient typeface,
damages, stains etc.,)
• Can something be done about this? (2)
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

6. Possible Solutions
• Manual Corrections
– Near Impossible
– VERY Expensive
• Using multiple OCR Programs
– They will still make mistakes
– But not the same mistakes
– Hopefully!
• Can something be done about this? (3)
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

7. Crowd Sourcing
• Each book contains 25000 words (Assume)
– Can we split them to 25 people, each correcting 1000 words?
– Or 50 people, each 500 words?
– Or 100 people, each 250 words?
– Or 2500 people, each 10 words?
– Or 25000 people, each 1 word?
• Sounds Stupid?
– Think again!
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

8. Dr. Luis von Ahn
• Associate Professor @ Carnegie Mellon University
• Coined the word CAPTCHA
• Pioneer in the field of Crowdsourcing
• Founder of the company reCAPTCHA (Later acquired
by Google)
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

9. reCAPTCHA
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

10. reCAPTCHA Process
• Step 1 : Using multiple OCR Programs
– Accept Matching Words
– Use Dictionary
– Flag “Problematic” Words
• Step 2 : reCAPTCHA
– Millions of users on various websites fill reCAPTCHA forms
• Proving they are not robots
• Proof reading text, One word at a time
– Similar entries are compared, before arriving at the final word
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

11. How It Works
Flagged Word Control Word
(Real CAPTCHA)
Remember “25000 people, Proof Reading 1 Word at a time”?
Not “Stupid” Anymore!
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

12. Few Statistics
• 100M+ reCAPTCHAs every day
• 96000+ Websites
– Most major websites use it
• Facebook, Twitter, CNN etc.,
• Security concerns exist!
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

13. What We Can Do
• Use reCAPTCHA instead of CAPTCHA in your
websites, wherever required
– Registration Forms, Blogs, Forums etc.,
– Easy to use Widgets
• Be proud when filling a reCAPTCHA form
– You are helping Google preserve books ☺
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

14. Applying Crowd Sourcing
• Can it solve some of your existing problems?
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

15. References, Image Credits
• https://www.youtube.com/watch?v=VoybhowC4LE
• http://www.nytimes.com/2011/03/29/science/29recaptcha.html?_r=1&
• http://techie-buzz.com/tech-news/recaptcha-crowdsourcing-ocr-google-
books.html
• http://www.google.com/recaptcha
• http://drupal.org/project/captcha
• http://www.captcha.net/
• http://www.brothersoft.com/cuneiform-ocr-4384.html
• http://www.compzets.com/view-upload.php?id=166&action=view
• http://en.wikipedia.org/
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.

16. Thank you
Story of reCAPTCHA www.crmit.com
© Copyright 2013 CRMIT. All rights reserved.