This paper studies reverse Turing tests to tell humans and computers apart. Contrary to classical Turing tests, the judge is not a human but a computer. These tests are often called Completely Automated Public Turing tests to tell Computers and Humans Apart (CAPTCHA). The main purpose of such test is avoiding automated usage of various services, preventing bots from spamming on forums, securing...

Audio CAPTCHA systems, which distinguish between software agents and human beings, are especially important for persons with visual disability. The popular approach is based on mixing-based methods (MBM), which use the mixed sounds of target speech and noises. We have proposed a deletion-based method (DBM) which uses the phonemic restoration effects. Our approach can control the difficulty of t...

In an on-line transaction, a client usually have to present some authenticators (password, user certificate or both) to the server. However, those authenticators are exposed to client-side malware such that the malware is able to obtain the server-client messages, or impersonate the user to build another “secure” channel with the server. The present paper aims to patch this client-side security...

This paper proposes JACI (Just Another CAPTCHA Implementation). JACI is an image-based CAPTCHA technology that requires users to match like images with their partner image in order to pass the test. JACI is not dependant on keyboard interaction which aids some forms of accessibility and does not require internationalisation. Interaction is controlled with a pointing device such as a mouse; as e...

Secure authentication is necessary for everyday applications, such as logging in to a personal computer, making a financial transaction or boarding an aircraft. We present a novel approach to user authentication in which biometric data related to human cognitive processes, in particular visual search, working memory and priming effect on automatic processing, are captured and used to identify u...

Human Interactive Proofs systems using CAPTCHA help protect services on the World Wide Web (WWW) from widespread abuse by verifying that a human, not an automated program, is making a request. To authenticate a user as human, a test must be passable by virtually all humans, but not by computer programs. For a CAPTCHA to be useful online, it must be easy to interpret by humans. In this paper, we...

A CAPTCHA is a program that can tell whether its user is a human or a computer. CAPTCHAs are used by many websites to differentiate between the bots (automated program) and the human. The main motive behind using the CAPTCHA is to prevent abuse from "bots," or automated programs usually written to generate spam. The CAPTCHA basically uses images in distorted form that is difficult to read by th...

Image-based CAPTCHA challenges have been successfully used to distinguish between humans and bots for a long time. However, image-based techniques are constantly broken by hackers, forcing web developers implement more robust security features new approaches in images. Modern-day can use many technologies break images automatically. These include OCR, Segmentation, erosion, threshold, flood fil...

INCORPORATING PRIVACY AND SECURITY FEATURES IN AN OPEN SOURCE SEARCH ENGINE The aim of this project was to explore and implement various privacy and security features in an open-source search engine and enhance the security and privacy capabilities of Yioop. Yioop, an open-source PHP search engine based on GPLv3 license, is designed and developed by Dr. Chris Pollett. We have enabled a crawl, s...