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