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CAPTCHA

CAPTCHA. What humans can do, But computers can not. Introduction. What does CAPTCHA mean? “ C ompletely A utomated P ublic T uring Test to Tell C omputers and H umans A part“

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CAPTCHA

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  1. CAPTCHA What humans can do, But computers can not. Matthias Neubauer

  2. Introduction • What does CAPTCHA mean? • “Completely Automated Public Turing Test to Tell Computers and Humans Apart“ • Founded by Luis von Ahn, Manuel Bluhm, Nick Hopper and John Langford from Carnegie Mellon School of Computer Science • What is a Turing Test? Matthias Neubauer

  3. Turing Test (1) • Turing: „One day, computers will be as intelligent as humans“ • Created a Test to prove it: • A Tester (für Turing a person) • 2 Contestians (1 Computer, 1 Human) in another room than the tester • Tester asks questions in text-form • Answers are returned in text-form Matthias Neubauer

  4. Turing Test (2) • If the Tester isn`t able to tell who`s the Human and who`s the Computer • => Then the computer must be as (or even more) intelligent as the human being. • CAPTCHA: The Tester doesn`t need to be human if it knows the correct answers Matthias Neubauer

  5. What is CAPTCHA for? • Helps blocking automated creations of email-accounts • Blocks Computers to vote automatically in online-polls • Blocks Search-Engine-Bots • and anything where humans don`t want computers to do something Matthias Neubauer

  6. Can we know that no computer can pass this test? • It`s wrong to believe, no computer will ever pass this tests • BUT: • It`s hard do develop a computer program for modern machines that can pass this tests • „Any program that can be used to break a CAPTCHA, can be used to solve an unsolved problem of the Artificial Intelligence“ Matthias Neubauer

  7. Hard Problem of the AI? • What is a „hard“ problem of the AI? • A problem, the AI-Community is aware of, but wasn`t able to solve • So it is very hard to develop a program for it • => If a CAPTCHA-breaking program can be used to solve a hard problem of the AI, it is very hard to break a CAPTCHA Matthias Neubauer

  8. Why public? • The developers WANT the hackers to break their CAPTCHAs • „This is how lazy cryptographers to AI“ • The results are good, and some text-based CAPTCHAs are already broken Matthias Neubauer

  9. What kinds of CAPTCHAS exist? (1) • Gimpy – a text-based CAPTCHA Matthias Neubauer

  10. What kinds of CAPTCHAS exist? (2) • Bongo – a shape-based CAPTCHA Matthias Neubauer

  11. What kinds of CAPTCHAS exist? (3) • Pix – a picture-based CAPTCHA • Eco – a sound-based CAPTCHA Matthias Neubauer

  12. „Bad“ Computers use humans! • Relink CAPTCHAs to human-users • Let humans do the work, and tell them it`s a game! Matthias Neubauer

  13. Resumee • Good to secure from „bad“ programs • Although wanted to be broken • => Use new / unbroken Captchas • Captcha – A wanted race with AI-Specialists covered as Hackers Matthias Neubauer

  14. Last Sentence • Who knows, maybe one day WE aren`t allowed anymore to create an E-Mail-Account, because we are not intelligent enough... Thank You for your Interest! Matthias Neubauer

  15. List of Sources • [1] Luis von Ahn, Manuel Bluhm und John Langford. The Captcha Project Homepage:http://www.captcha.net • [2] Luis von Ahn, Manuel Bluhm und John Langford. Telling Humans and Computers Apart (Automatically):http://www.cs.cmu.edu/~biglou/captcha.pdf • [3] Andrew Hodges. The Alan Turing Internet Scrapbook:http://www.turing.org.uk/turing/scrapbook/test.html • [4] Luis von Ahn. The ESP Game:http://www.espgame.org Matthias Neubauer

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