1. Human Based Character Recognition Via Web-Security Measures Original Research By Luis Von Ahn Benjamin Maurer Colin McMillen David Abraham Manuel Blum Presented BY : Md. ShihabUddin Roll: 0607029, CSE,KUET This paper was published in Science Express on 14 August 2008 by the American Association for the Advancement of Science (AAAS).

3. Why Re-inventing Captcha?

4. Digitizing Books with Re-captcha

5. Re-Captcha IN USE

6. RE-CAPTCHA CURRENT

8. CAPTCHA’S CAPTCHA@yahoomail 4

9. CAPTCHA’S CAPTCHA@HOTMAIL 5

11. Colorful images with distorted text at the bottom of web registration forms.

13. Data collection

14. Preventing worms & spam

16. Daily solved CAPTCHA’S= more than 200 millions

17. Human hours lost= more than 150,000 hours a day.

19. Solution is: Re-CAPTCHAor Re-invented CAPTCHA

20. Digitizing Books: Normal Approach SCAN O C R Problem is OCR is not perfect. Cannot Decipher 20% of the word’s whereas Re-CAPTCHA can 99%

21. Digitizing Books: Re-CAPTCHA Approach WORD’s that OCR Cannot Read SCANNED BOOK Randomly Distorted Image of WORD

22. Digitizing Books: Re-CAPTCHA Approach Randomly Distorted Image of WORD Added in Random Order Known Distorted Control Word Re-CAPTCHA

25. Re-CAPTCHA IN USE Re-CAPTCHA IN TWITTER

26. Re-CAPTCHA IN USE Re-CAPTCHA IN FACEBOOK

27. Words Digitized Per Day

28. Re-CAPTCHA IN USE Digitization Rate: 4 Million Words Per Day Approximately 160 Books(400 pages,250 words per page) Per Day This ratio’s are very old, current rate is very high, cause Facebok+Twitter now have nearly 500 million users & using Re-CAPTCHA.

29. Re-CAPTCHA IN USE Words are coming from: The NEWYORK TIMES(1851-1980) Internet Archive Stored In: Google News Google Books

30. Re-CAPTCHA CURRENT GOOGLE Acquired Re-CAPTCHA LUIS VON AHN works as Research Scientist at GOOGLE along with his job at Carnegie Mellon. LUIS VON AHN’s co-workers who worked on Re-CAPTHA are now working on GOOGLE. LUIS VON AHN awarded a lot for inventing CAPTCHA & Re-CAPTCHA including Mc Arthur Fellowship, One of The Best 10 Computer Scientist of the world, Pioneer of Human Computation.

31. REFERENCES Paper from www.sciencmag.org http://www.captcha.net http://www.re-captcha.net http://www.captcha.net http://www.cs.cmu.edu/~biglou Homepage of LUIS VON AHN Pictures from Web: Facebook,Twitter,Google & other sites

32. Q & A

33. Thank You