A CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is an automatic security mechanism used to determine whether the user is a human or a malicious computer program. It is a program that generates and grades tests that are human solvable, but intends to be beyond the capabilities of current computer programs. CAPTCHA should be designed to be very easy for huma...

Simple, universally applicable strategies can help any captchaprotected system resist automated attacks and can improve the ability of administrators to detect attacks. The strategies discussed here cause an exponential increase in the difficulty faced by automated attackers, while only increasing the inconvenience for human users in an approximately linear manner. These strategies are characte...

In this paper we explore object recognition in clutter. We test our object recognition techniques on Gimpy and EZGimpy, examples of visual CAPTCHAs. A CAPTCHA (“Completely Automated Public Turing test to Tell Computers and Humans Apart”) is a program that can generate and grade tests that most humans can pass, yet current computer programs can’t pass. EZ-Gimpy (see Fig. 1, 5), currently used by...

Many CAPTCHA proposals have shortcomings in their design or implementation that make themmuch weaker than intended. In this paper we study Captcha2, a commercial algorithm, as a means of showing typical flaws that make many CAPTCHAs prone to successful low-cost attacks. The attack we present makes no use of any AI techniques, not affecting the resilience of the original AI problem this CAPTCHA ...

CAPTCHAs are a widely deployed mechanism to distinguish a legitimate human user from a computerized program trying to abuse online services. Attackers, however, have devised a clever and an economical way to bypass the security provided by CAPTCHAs by simply relaying CAPTCHA challenges to remote human-solvers. Most existing varieties of CAPTCHAs are completely vulnerable to such relay attacks, ...

This work focuses on development of an alternative aural CAPTCHA technology based on a speech transcription task. The principal goals are (1) to provide a better quality of service for visually impaired web users who currently have few alternatives for accessing web services protected by CAPTCHAs based on visual perception tasks, (2) as a side effect of CAPTCHA use, collect meaning data, such a...

Completely Automatic Public Turing test to tell Computers and Humans Apart (CAPTCHA) is a HIP (Human interactive Proof) system. CAPTCHAs are used to improve the security of Internet based applications in order to ensure that a web based application which is intended to be used by a human being is not maliciously used by Artificially Intelligent programs called bots. As the current CAPTCHA metho...

Online detection of protection orbit round as an important part of the train, the tread wear parameters traffic safety is important. Like the wheel of the measurement techniques based on optical screenshots Dimensions dynamic detection 'access to a complete round of the contour image is essential. For the round image features is proposed based on region developing the round image segmentation a...

Any Web user is a potential knowledge contributor, but it remains a challenge to make them devote their time contributing to some purpose. In order to align individual with social interests, we selected the CAPTCHA Web resource protection application to embed knowledge elicitation within the users' main task of accessing a Web resource. Consequently, unlike previous knowledge acquisition approa...

Cloud computing is simply a metaphor for the internet. User does not required knowledge, control, and ownership in the computer infrastructure. User simply access or rent the software and paying only for what they use. Advantage of cloud computing is huge like Broad network access, Cost effectiveness, Rapid elasticity, Measured services, On-Demand service, Resource pooling, Location independenc...