Post on 05-Apr-2018
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ASEMINAR
ON
CAPTCHA
Presented by:ABHINAY MAURYAB.Tech 3rd Yr.
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Contents
Introduction & History
Examples of Captcha
Types of Captcha Characteristics of Captcha
Applications
Benefits and Drawbacks
Reference
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Introduction
A CAPTCHA is a program that can generateand grade tests that humans can pass butcurrent computer programs cannot. Forexample, humans can read distorted text,but current computer programs can't read it:
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A CAPTCHA is a type of challenge-response testused in computing to ensure that the response isnot generated by a computer. The process usuallyinvolves one computer (a server) asking a user tocomplete a simple test which the computer is ableto generate and grade.
http://en.wikipedia.org/wiki/Challenge-response_authenticationhttp://en.wikipedia.org/wiki/Computinghttp://en.wikipedia.org/wiki/Server_(computing)http://en.wikipedia.org/wiki/File:Modern-captcha.jpghttp://en.wikipedia.org/wiki/Server_(computing)http://en.wikipedia.org/wiki/Computinghttp://en.wikipedia.org/wiki/Challenge-response_authenticationhttp://en.wikipedia.org/wiki/Challenge-response_authenticationhttp://en.wikipedia.org/wiki/Challenge-response_authentication8/2/2019 New Captcha
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History of Captcha
The term "CAPTCHA" was created in 2000 byLuis von Ahn, Manuel Blum, Nicholas J. Hopperof Carnegie Mellon University.
CAPTCHA code was created to stop automatedcomputer spam robots from filling out forms,
harvesting email addresses, and then sendingout countless spam emails.
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CAPTCHA
Completely
Automated
Public Turing test to tell
Computers and
Humans Apart
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Example of Captcha
http://en.wikipedia.org/wiki/File:KCAPTCHA_with_crowded_symbols.gifhttp://en.wikipedia.org/wiki/File:Modern-captcha.jpghttp://en.wikipedia.org/wiki/File:Captcha.jpg8/2/2019 New Captcha
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Some Weak CAPTCHAs
From Paypal
From YahoosBriefcase
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Some CAPTCHAs that may betoo hard for people
From Yahoo:
From Passport:
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Types of Captcha
Text Based
Graphic Based
Audio based
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Text Based Captcha
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Graphic BasedCAPTCHA
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Audio Based CAPTCHA
- Pick a word or a sequence of numbers atrandom
-Render them into an audio clip-Distort the audio clip
-Ask the user to identify and type the word
or numbers
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A CAPTCHA system is a means ofautomatically generating new challengeswhich:
- Current software is unable to solveaccurately.
- Most humans can solve
- Does not rely on the type of CAPTCHAbeing new to the attacker.
Characteristics
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Applications
* Free e-mail services
* Online polls
* Dictionary attacks* Newsgroups, Blogs, etc
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Benefits
The database already exists and is public
The database is constantly being updatedand maintained
Adding concrete objects to the dictionary is
virtually instantaneous
Distortion prevents caching hacks
Quick expiration limits streaming hacks
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Drawbacks Not accessible to people with disabilities
(which is the case of most CAPTCHAs)
Relies on Googles infrastructure
Unlike CAPTCHAs using random letters andnumbers, the number of challenge words is
limited
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Reference
1. www.google.com
2. www.wikipedia.com3. www.answer.com
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Make your own CAPTCHA
A web site that offers you the means:
www.codeproject.com/KB/aspnet/
CaptchaImage.aspx For a general tutorial see:
www.theopavlidis.com/technology/
captcha/tutorial.htm
http://www.codeproject.com/KB/aspnet/%0BCaptchaImage.aspxhttp://www.codeproject.com/KB/aspnet/%0BCaptchaImage.aspxhttp://www.theopavlidis.com/technology/%0Bcaptcha/tutorial.htmhttp://www.theopavlidis.com/technology/%0Bcaptcha/tutorial.htmhttp://www.theopavlidis.com/technology/%0Bcaptcha/tutorial.htmhttp://www.theopavlidis.com/technology/%0Bcaptcha/tutorial.htmhttp://www.theopavlidis.com/technology/%0Bcaptcha/tutorial.htmhttp://www.codeproject.com/KB/aspnet/%0BCaptchaImage.aspxhttp://www.codeproject.com/KB/aspnet/%0BCaptchaImage.aspxhttp://www.codeproject.com/KB/aspnet/%0BCaptchaImage.aspx8/2/2019 New Captcha
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THANK YOU