A Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a widely used security defense mechanism that is utilized by service providers to determine whether the entity interacting with their system is a human and not a malicious agent. Motivated by recent research which underpins the necessity for designing more userfriendly CAPTCHA, this paper investigates the ...

With data theft and computer break-ins becoming increasingly common, there is a great need for secondary authentication to reduce automated attacks while posing a minimal hindrance to legitimate users. CAPTCHA is one of the possible ways to classify human users and automated scripts. Though textbased CAPTCHAs are used inmany applications, they pose a challenge due to language dependency. In thi...

A Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is designed to distinguish humans from machines. Most of the existing tests require reading distorted text embedded in a background image. However, many existing CAPTCHAs are either too difficult for humans due to excessive distortions or are trivial for automated algorithms to solve. These CAPTCHAs also suff...

Recent document image understanding R&D intended to protect Internet services against abuse by programs is summarized. The accelerating pace of introduction of working CAPTCHAs — completely automatic public Turing tests to tell computers and humans apart — is reported, and the ability of these CAPTCHAs to resist attack is critiqued. Attacks on PARC’s ‘BaffleText’ CAPTCHA by the DIA, CV, and sec...

In this paper, we have proposed a system to grade CAPTCHA strength, according to various parameters determined by breaking the CAPTCHA. There are basically four major steps involved in the system.First step is preprocessing which includes – binarization and noise removal.Second step is segmenting the image into individual characters. Third step is to obtain skeletons of characters i.e., Thinnin...

A Completely Automated Public Turing test to tell Computer and Humans Apart (CAPTCHA) is a variation of the Turing test, in which a challenge is used to distinguish humans from computers (‘bots’) on the internet. They are commonly used to prevent the abuse of online services; for example, malicious users have written automated programs that signup for thousands of free email accounts and send S...