The massive and automated access to Web resources through robots has made it essential for Web service providers to make some conclusion about whether the "user" is a human or a robot. A Human Interaction Proof (HIP) like Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) offers a way to make such a distinction. CAPTCHA is a reverse Turing test used by Web serv...

Many security primitives are based on hard mathematical problems. Using hard AI problems for security is emerging as an exciting new paradigm,but has been under explored a novel family of graphical password systems built on top of Captcha technology,which we call Captcha as a graphical passwords (CaRP).. CaRP addresses a such as online guessing attacks, relay attacks, and, if combined withdual-...

CAPTCHA is an acronym that stands for Completely Automated Public Turing Test to tell Computers and Humans Apart (CAPTCHA), it a good example of authentication system can be used determine the true identity any user. It serves as security measure prevent attack caused by web bots (automatic programs) during online transaction. come text-based or image-based depending on project programmer. The ...

CAPTCHAs are tests that distinguish humans from software robots in an online environment [3, 14, 7]. We propose and implement three CAPTCHAs based on naming images, distinguishing images, and identifying an anomalous image out of a set. Novel contributions include proposals for two new CAPTCHAs, the first user study on image recognition CAPTCHAs, and a new metric for evaluating CAPTCHAs.

In this paper we present a new CAPTCHA system (Completely Automated Turing Test To Tell Computers and Humans Apart). This proposal, SemCAPTCHA, is motivated by an increasing number of broken OCR-based CAPTCHA systems and it is based not only on text recognition but also on text understanding. We describe SemCAPTCHA from both user’s perspective and system’s perspective and compare it to some cur...

Code voting provides an appropriate technology to address the secure platform problem of remote Internet voting, but it is not particularly user-friendly. In this paper, we propose the use of CAPTCHAan acronym standing for Completely Automated Public Turing tests to tell Computers and Humans Apart to improve the user-friendliness of code voting, discuss the security of CAPTCHAbased code voting,...

The use of colour in user interfaces is extensive. It is typically a usability issue, and has rarely caused any security concerns. In this article, we show that the use of colours in the design of CAPTCHA, a standard security technology that has found widespread applications in commercial websites, can have interesting but critical implications on both security and usability. © 2010 University ...

Over the last years, most websites where users can register (e.g., email providers and social networks) adopted CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) as a countermeasure for automated attacks. The battle of wits between designers and attackers of CAPTCHAs led to current ones being annoying and hard to resolve for users, while still being vulnerabl...

The advent of electronic voting gives rise to a new threat: Adversaries may execute undetectable, automated attacks against the system. Elections are often secured through complex policies, which may be difficult to enforce; Completely Automated Public Turing Tests to Tell Computers and Humans Apart (CAPTCHAs) provide an inexpensive alternative. The goal of this study is to introduce a unique a...