Download Problem Statement:-

LGNSCOE, Anjaneri
Department of Computer Engineering
(GR:C)
ASSIGNMENT NO: 2
Implement a program to generate and verify CAPTCHA image/string.
TE Comp (SEMESTER I)
1
Programming Laboratory-II
LGNSCOE, Anjaneri
Department of Computer Engineering
Problem Statement:
Implement a program to generate and verify CAPTCHA image/string.
THEORY
A CAPTCHA (an acronym for "Completely Automated Public Turing test to tell Computers and
Humans Apart") is a type of challenge-response test used in computing to determine whether or not
the user is human.
It is used to differentiate between humans and robots.This form of CAPTCHA requires that the user
type to the letters of a distorted image, sometimes with the addition of an obscured sequence of
letters or digits that appears on the screen. This helps in differentiating between a program and
visualisation. Because the test is administered by a computer, in contrast to the standard Turing test
(test of a machine's ability to exhibit intelligent behaviour) that is administered by a human, a
CAPTCHA is sometimes described as a reverse Turing test.
History:
The term was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas J. Hopper of
Carnegie Mellon University and John Langford of IBM. The most common type of CAPTCHA was
first invented by Mark D. Lillibridge, Martin Abadi, Krishna Bharat and Andrei Z. Broder.
Characteristics:
1) CAPTCHAs are by definition fully automated, requiring little human maintenance or
intervention to administer. This has obvious benefits in cost and reliability.
2) The algorithm used to create the CAPTCHA must be made public, though it may be covered by a
patent. This is done to demonstrate that breaking it requires the solution to a difficult problem in the
field of artificial intelligence (AI) rather than just the discovery of the (secret) algorithm, which
could be obtained through reverse engineering or other means.
3) Modern text-based CAPTCHAS are designed such that they require the simultaneous use of three
separate abilities—invariant recognition (ability to recognize the large amount of variation in the
shapes of letters), segmentation, and parsing—to correctly complete the task with any consistency.
4) There are nearly an infinite number of versions for each character that a human brain can
successfully identify. The same is not true for a computer, and teaching it to recognize all those
differing formations is an extremely challenging task.
5) Segmentation, or the ability to separate one letter from another, is also made difficult in
CAPTCHAs, as characters are crowded together with no white space in between.
6) Unlike computers, humans excel at differentiating between unusual fonts. While segmentation
and recognition are two separate processes necessary for understanding an image for a computer,
they are part of the same process for a person. Human brain will not be fooled by variations in
letters.
Application:
TE Comp (SEMESTER I)
2
Programming Laboratory-II
LGNSCOE, Anjaneri
Department of Computer Engineering
CAPTCHAs are used to prevent bots from using various types of computing services or
collecting certain types of sensitive information. Applications include preventing bots from taking
part in online polls, registering for free email accounts (which may then be used to send spam) and
collecting email addresses. CAPTCHAs can prevent bot-generated spam by requiring that the
(unrecognized) sender pass a CAPTCHA test before the email message is delivered, but the
technology can also be exploited by spammers by impeding OCR detection of spam in images
attached to email messages.
Relation with AI:
While used mostly for security reasons, CAPTCHAs also serve as a benchmark task for
artificial intelligence technologies. Any program that passes the tests generated by a CAPTCHA can
be used to solve a hard unsolved AI problem
The arguement is that the advantages of using hard AI problems as a means for security are
twofold. Either the problem goes unsolved and there remains a reliable method for distinguishing
humans from computers, or the problem is solved and a difficult AI problem is resolved along with
it. In the case of image and text based CAPTCHAs, if an AI were capable of accurately completing
the task without exploiting flaws in a particular CAPTCHA design, then it would have solved the
problem of developing an AI that is capable of complex object recognition in scenes.
reCAPTCHA:
reCAPTCHA is a free service provided by google to protect your website from spam and abuse.
reCAPTCHA uses an advanced risk analysis engine and adaptive CAPTCHAs to keep automated
software from engaging in abusive activities on your site. It does this while letting your valid users
pass through with ease.
reCAPTCHA offers more than just spam protection. Every time our CAPTCHAs are solved,
that human effort helps digitize text, annotate images, and build machine learning datasets. This in
turn helps preserve books, improve maps, and solve hard AI problems.
In this assignment, we have designed the code using java.
Explanation of the program:
Note: Student is supposed to write explanation for code of the given problem statement.
Mathematical Model:
Note: Student is supposed to write mathematical model for the given problem statement.
Conclusion
Hence, we have successfully studied concept of generation and verification of CAPTCHA image.
TE Comp (SEMESTER I)
3
Programming Laboratory-II
LGNSCOE, Anjaneri
TE Comp (SEMESTER I)
Department of Computer Engineering
4
Programming Laboratory-II