Download Captcha

CAPTCHA
What humans can do,
But computers can not.
24.05.2017
Matthias 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?
24.05.2017
Matthias Neubauer
Turing Test (1)


Turing: „One day, computers will be as
intelligent as humans“
Created a Test to prove it:




24.05.2017
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
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
24.05.2017
Matthias 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
24.05.2017
Matthias Neubauer
Can we know that no
computer can pass this test?


It`s wrong to believe, no computer will ever
pass this tests
BUT:


24.05.2017
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
Hard Problem of the AI?

What is a „hard“ problem of the AI?



24.05.2017
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
Why public?



The developers WANT the hackers to
break their CAPTCHAs
„This is how lazy cryptographers to AI“
The results are good, and some textbased CAPTCHAs are already broken
24.05.2017
Matthias Neubauer
What kinds of CAPTCHAS
exist? (1)

Gimpy – a text-based CAPTCHA
24.05.2017
Matthias Neubauer
What kinds of CAPTCHAS
exist? (2)

Bongo – a shapebased CAPTCHA
24.05.2017
Matthias Neubauer
What kinds of CAPTCHAS
exist? (3)

Pix – a picture-based CAPTCHA

Eco – a sound-based CAPTCHA
24.05.2017
Matthias Neubauer
„Bad“ Computers use humans!

Relink CAPTCHAs to human-users

Let humans do the work, and tell them
it`s a game!
24.05.2017
Matthias Neubauer
Resumee

Good to secure from „bad“ programs



Although wanted to be broken
=> Use new / unbroken Captchas
Captcha – A wanted race with AISpecialists covered as Hackers
24.05.2017
Matthias 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!
24.05.2017
Matthias Neubauer
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
24.05.2017
Matthias Neubauer