28-02-2013, 12:29 PM
Completely Automated Public Turing test to tell Computer and Human Aparts
Completely Automated.pptx (Size: 2.44 MB / Downloads: 24)
INTRODUCTION
Completely Automated Public Turing test to tell Computer and Human Aparts
This is full form of CAPTCHA and also define the purpose of CAPTCHA
Actually CAPTCHA is used as simple puzzle hurdle Which restricts various automated program to sign up E-mail accounts, cracking passwords, spam sending,
HISTORY
The term “CAPTCHA” was coined in 2000 by Luis Von Ahn, Manuel Blum, Nicholas Hopper and John Langford
Actually the concept of CAPTCHA is motivated by real-world problem faced by internet companies such as yahoo and Alta vista
This companies offer free email account, intended for use by humans
EZ-Gimpy:
A modified version of Gimpy
Yahoo used this version in Messenger
Has only 1 random string of characters
Not a dictionary word, so not prone to dictionary attack
Not a good implementation, already broken by OCRs
PIX:
Uses a large database of labelled images
It shows a set of images, user has to recognize the common feature among those
E.g., Pick the common characteristic among the following four pictures-----”Aeroplane”
Conclusion
CAPTCHAs are an effective way to counter bots and reduce spam
CAPTCHAs as useful as data sets for studying object recognition
They serve dual purpose– help advance AI knowledge
Applications are varied– from stopping bots to character recognition & pattern matching
Some issues with current implementations represent challenges for future improvements