Abstract: A CAPTCHA is a type of challenge-response test used in computing to determine whether the user is human. "CAPTCHA" is a contrived acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart", trademarked by Carnegie Mellon University. A CAPTCHA involves one computer (a server) which asks a user to complete a test. While the computer is able to generate and grade the test, it is not able to solve the test on its own. Because computers are unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human. A CAPTCHA is sometimes described as a reverse Turing test, because it is administered by a machine and targeted to a human, in contrast to the standard Turing test that is typically administered by a human and targeted to a machine. For example, human can generally read degraded images, but OCR machines cannot. CAPTCHAs are designed to prevent bots – programs that pose as humans on the Internet – from abusing internet services. Bots, driven not to dominate but to sell, sign up for thousands of free email accounts every minute, sending millions of spam messages from them. They infiltrate chat rooms, collecting personal information and posting links to promotional sites. They generate worms, break password systems, invade privacy, and drain resources. To defend e-commerce systems from bots, an increasing number of companies are arming themselves with CAPTCHAs. For example, users registering on Yahoo must first correctly recognize a distorted word displayed against a cluttered background and type it into a box to prove they are human. Such reading-based CAPTCHAs exploit the large gap between humans and machines in their ability to read images of text.
Keywords: Captcha, Images, OCR machines, Turing test.
Title: Reusable Captcha Security Engine
Author: Mr. Ujwal Namdeo Abhonkar, Mr. Swapnil Mohan Phalak, Mrs. Pooja Ujwal Abhonkar
International Journal of Computer Science and Information Technology Research
ISSN 2348-1196 (print), ISSN 2348-120X (online)
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