1. 13.09.2015Matthias Neubauer CAPTCHA What humans can do, But computers can not.

2. 13.09.2015Matthias Neubauer 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?

3. 13.09.2015Matthias Neubauer 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

4. 13.09.2015Matthias Neubauer 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

5. 13.09.2015Matthias Neubauer 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

6. 13.09.2015Matthias Neubauer 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“

7. 13.09.2015Matthias Neubauer 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

8. 13.09.2015Matthias Neubauer 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

9. 13.09.2015Matthias Neubauer What kinds of CAPTCHAS exist? (1) Gimpy – a text-based CAPTCHA

10. 13.09.2015Matthias Neubauer What kinds of CAPTCHAS exist? (2) Bongo – a shape- based CAPTCHA

11. 13.09.2015Matthias Neubauer What kinds of CAPTCHAS exist? (3) Pix – a picture-based CAPTCHA Eco – a sound-based CAPTCHA

12. 13.09.2015Matthias Neubauer „Bad“ Computers use humans! Relink CAPTCHAs to human-users Let humans do the work, and tell them it`s a game!

13. 13.09.2015Matthias Neubauer 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

14. 13.09.2015Matthias Neubauer 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!

15. 13.09.2015Matthias Neubauer List of Sources [1] Luis von Ahn, Manuel Bluhm und John Langford. The Captcha Project Homepage: http://www.captcha.net 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 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 http://www.turing.org.uk/turing/scrapbook/test.html [4] Luis von Ahn. The ESP Game: http://www.espgame.org http://www.espgame.org