New Captcha

8/2/2019 New Captcha

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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_authentication


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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.jpg


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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.aspx


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THANK YOU

Documents

New Captcha