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Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
Re capthca(msu on cse 4120)
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Re capthca(msu on cse 4120)

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  • 1. Human Based Character Recognition Via Web-Security Measures <br />Original Research By<br />Luis Von Ahn<br /> Benjamin Maurer<br /> Colin McMillen<br /> David Abraham<br /> Manuel Blum<br />Presented BY : <br />Md. ShihabUddin<br />Roll: 0607029, CSE,KUET <br />This paper was published in Science Express on 14 August 2008 by the American Association for the Advancement of Science (AAAS).<br />
  • 2. Outline<br /><ul><li>Captcha’s
  • 3. Why Re-inventing Captcha?
  • 4. Digitizing Books with Re-captcha
  • 5. Re-Captcha IN USE
  • 6. RE-CAPTCHA CURRENT
  • 7. References </li></li></ul><li>CAPTCHA’S<br />CAPTCHA @GMAIL <br />
  • 8. CAPTCHA’S<br />CAPTCHA@yahoomail<br />4<br />
  • 9. CAPTCHA’S<br />CAPTCHA@HOTMAIL<br />5<br />
  • 10. CAPTCHA’S<br /><ul><li>A CAPTCHA(COMPLETELY AUTOMATED TURING TEST TO TELL COMPUTERS & HUMANS APART) is a program that can tell its user whether a human or computer.
  • 11. Colorful images with distorted text at the bottom of web registration forms.
  • 12. Only can be deciphered by humans, computer programs or autobot's can’t .</li></ul>Applications: <br /><ul><li>Free e-mail services, social networks,blogs
  • 13. Data collection
  • 14. Preventing worms & spam
  • 15. Preventing dictionary attacks </li></li></ul><li>Why Re-inventing CAPTCHA <br />A calculation: <br /><ul><li>Time takes to solve a CAPTCHA= 10 seconds
  • 16. Daily solved CAPTCHA’S= more than 200 millions
  • 17. Human hours lost= more than 150,000 hours a day.
  • 18. 6% of world’s population type’s CAPTCHA everyday</li></li></ul><li>Why Re-inventing CAPTCHA<br />Though CAPTCHA’S prevents spam’s & autobot’s but this human effort is totally wasted everyday.<br />Is there anyway to use this HUMAN effort for something good?<br />
  • 19. Solution is: Re-CAPTCHAor Re-invented CAPTCHA <br />
  • 20. Digitizing Books: Normal Approach<br />SCAN<br />O<br />C R<br />Problem is OCR is not perfect. <br />Cannot Decipher 20% of the word’s whereas Re-CAPTCHA can 99%<br />
  • 21. Digitizing Books: Re-CAPTCHA Approach<br />WORD’s that OCR Cannot Read <br />SCANNED BOOK<br />Randomly Distorted Image of WORD <br />
  • 22. Digitizing Books: Re-CAPTCHA Approach<br />Randomly Distorted Image of WORD <br />Added in Random Order <br />Known Distorted Control Word <br /> Re-CAPTCHA <br />
  • 23. Digitizing Books: Re-CAPTCHA Approach<br /> Re-CATCHA <br /><ul><li>One Re-CAPTCHA is sent to many users.Same word typed by 3 users & matches with OCR Guess, word digitized
  • 24. Skipped by 6 users to type Re-CAPTCHA,WordConsidered Un-readable </li></li></ul><li>Re-CAPTCHA IN USE <br />FREE TO USE <br /> Popular Users<br />Facebook<br />CraiglistMore than 100,000 Websites <br />Twitter<br />
  • 25. Re-CAPTCHA IN USE <br />Re-CAPTCHA IN TWITTER <br />
  • 26. Re-CAPTCHA IN USE <br />Re-CAPTCHA IN FACEBOOK<br />
  • 27. Words Digitized Per Day <br />
  • 28. Re-CAPTCHA IN USE <br />Digitization Rate:<br />4 Million Words Per Day<br />Approximately 160 Books(400 pages,250 words per page) Per Day<br />This ratio’s are very old, current rate is very high, cause Facebok+Twitter now have nearly 500 million users & using Re-CAPTCHA.<br />
  • 29. Re-CAPTCHA IN USE <br /> Words are coming from:<br />The NEWYORK TIMES(1851-1980)<br />Internet Archive <br />Stored In:<br />Google News<br />Google Books<br />
  • 30. Re-CAPTCHA CURRENT<br />GOOGLE Acquired Re-CAPTCHA <br />LUIS VON AHN works as Research Scientist at GOOGLE along with his job at Carnegie Mellon. <br />LUIS VON AHN’s co-workers who worked on Re-CAPTHA are now working on GOOGLE.<br />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.<br />
  • 31. REFERENCES <br />Paper from www.sciencmag.org<br />http://www.captcha.net<br />http://www.re-captcha.net<br />http://www.captcha.net<br />http://www.cs.cmu.edu/~biglou Homepage of LUIS VON AHN<br />Pictures from Web: Facebook,Twitter,Google & other sites <br />
  • 32. Q & A <br />
  • 33. Thank You <br />

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