CAPTCHA, which stands for Completely Automated Public Turing test to tell computers and humans apart, was introduced in the early 2000s to prevent fraud submissions on the Internet. The Turing Test, named after Alan Turing, evaluates a machine's intelligence, and the Loebner Prize offers rewards for passing this test, though no program has yet achieved the success rate aimed for. Various types of CAPTCHA exist, but advancements in machine learning, such as those made by Vicarious, have shown that it's possible to break some CAPTCHA systems.

1. What is CAPTCHA ?

2. Introduction to
‘CAPTCHA’

4. What is CAPTCHA ?
• CAPTCHA stands for Completely
Automated Public Turing Test to
tell Computers and Humans
Apart.
• In the early 2000 it was first implemented in
famous search engine ALTA VISTA to prevent
fraud submission of URLs.
• It is a type of challenge-response test used
in computing to determine whether or not the
user is human.
Source: www.tutorialspoint.com/

5. TURING TEST
(An Imitation Game)
• Turing test is a test named after the father of
modern computer science- Alan Turing.
• It is used to determine the intelligence level of
a machine.
• If a machine passes the Turing test, it is said to
be ‘intelligent’.
Source: www.tutorialspoint.com/

6. Now the question is
What is Turing Test?

7. Turing Test
Image Source: http://www.clarkoncode.com/What-is-the-Turing-Test/

8. The Loebner Prize
• Dr. Hugh Loebner pledged $100,000 to the
first entrant that could pass the test (1991).
• Since 1995, there has been an annual
competition, which has yet to find a winner.
• While small prizes are given out to the most
"human-like" computer, no program has had
the 50% success Turing aimed for.
• Steven Harnad has proposed the "Total
Turing Test"

9. Types of Captcha
S. No Title Example
01 Text-based Captcha
02 Re-CAPTCHA
03 Mathematical
Captcha
04 Image-based Captcha
05 Logic-based Captcha
06 3D Captcha
07 Commercial Captcha
Image Source: www.google.com/
Author highly acknowledge all the sources.

10. Is it impossible to break Captcha?
----The answer is No ---
• Vicarious Company (Founded in 2010) claimed
that they have designed a software based on
machine learning.
• Vicarious software can read images nearly as
well as humans and can crack a CAPTCHA 90
percent of the time.
• One more claim is there in market that a
security researcher has defeated the ‘Audio
Captcha’ by using Google speech recognition
system.

11. THANKS