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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. Shihab Uddin 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).
Outline CAPTCHA’S
WHY RE-INVENTING CAPTCHA?DIGITIZING BOOKS WITH RE-CAPTCHARE-CAPTCHA IN USE RE-CAPTCHA CURRENTREFERENCES
CAPTCHA’S
CAPTCHA @GMAIL
CAPTCHA’S
4
CAPTCHA@yahoomail
CAPTCHA’S
5
CAPTCHA@HOTMAIL
CAPTCHA’S
A CAPTCHA(COMPLETELY AUTOMATED TURING TEST TO TELL COMPUTERS & HUMANS APART) is a program that can tell its user whether a human or computer.
Colorful images with distorted text at the bottom of web registration forms.
Only can be deciphered by humans, computer programs or autobot's can’t .
APPLICATIONS: Free e-mail services, social networks,blogs Data collection Preventing worms & spam Preventing dictionary attacks
Why Re-inventing CAPTCHA
A calculation: Time takes to solve a CAPTCHA= 10 seconds Daily solved CAPTCHA’S= more than 200
millions Human hours lost= more than 150,000 hours
a day. 6% of world’s population type’s CAPTCHA
everyday
Why Re-inventing CAPTCHA
Though CAPTCHA’S prevents spam’s & autobot’s but this human effort is totally
wasted everyday.
Is there anyway to use this HUMAN effort for
something good?
Solution is: Re-CAPTCHAor Re-invented CAPTCHA
Digitizing Books: Normal Approach
SCAN
OC R
Problem is OCR is not perfect.
Cannot Decipher 20% of the word’s whereas Re-
CAPTCHA can 99%
Digitizing Books: Re-CAPTCHA Approach
SCANNED BOOK
WORD’s that OCR Cannot Read
Randomly Distorted Image of WORD
Digitizing Books: Re-CAPTCHA Approach
Randomly Distorted Image of WORD
Known Distorted Control Word
Re-CAPTCHA
Added in Random Order
Digitizing Books: Re-CAPTCHA Approach
Re-CATCHA
One Re-CAPTCHA is sent to many users.Same word typed by 3 users & matches with OCR Guess, word digitized
Skipped by 6 users to type Re-CAPTCHA,Word Considered Un-readable
Re-CAPTCHA IN USE
FREE TO USE
Popular UsersFacebookCraiglist More than 100,000 Websites Twitter
Re-CAPTCHA IN USE
Re-CAPTCHA IN TWITTER
Re-CAPTCHA IN USE
Re-CAPTCHA IN FACEBOOK
Words Digitized Per Day
Re-CAPTCHA IN USE
Digitization Rate:1. 4 Million Words Per Day2. Approximately 160 Books(400 pages,250
words per page) Per Day3. This ratio’s are very old, current rate is very
high, cause Facebok+Twitter now have nearly 500 million users & using Re-CAPTCHA.
Re-CAPTCHA IN USE
Words are coming from:1. The NEWYORK TIMES(1851-1980)2. Internet Archive Stored In:3. Google News4. Google Books
Re-CAPTCHA CURRENT
1. GOOGLE Acquired Re-CAPTCHA 2. LUIS VON AHN works as Research Scientist at
GOOGLE along with his job at Carnegie Mellon. 3. LUIS VON AHN’s co-workers who worked on Re-
CAPTHA are now working on GOOGLE.4. 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.
REFERENCES
1. Paper from www.sciencmag.org2. http://www.captcha.net3. http://www.re-captcha.net4. http://www.captcha.net5. http://www.cs.cmu.edu/~biglou Homepage
of LUIS VON AHN6. Pictures from Web: Facebook,Twitter,Google
& other sites
Q & A
THANK YOU