The landscape of the World Wide Web today consists of a vast amount of services. While most of them are offered for free, the service providers prohibit their malicious usage by automated scripts. To enforce this policy, Captchas have emerged as a reliable method to setup a Turing test to distinguish between human and computers. Image recognition Captchas as one type of Captchas promise high hu...

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-...

Prof. von Ahn began his discussion of the possibilities of augmented intelligence with a description of his invention (with colleagues) of the Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) [1], often encountered as a random sequence of distorted letters, which human Web users have to repeat to prove that they are indeed human, rather than a computer progra...

INTRODUCTION In recent years, outcome assessment related to orthopedic surgeries has increasingly focused on patient-reported questionnaires. The Oxford Hip Score (OHS), self-administered questionnaire, is a reliable, valid, and responsive instrument for assessing hip in patients undergoing Arthroplasty. METHODS The study involved 105 adult Persian-speaking patients admitted for primary Total...

BACKGROUND The Oxford Knee Score (OKS) is a short patient-reported outcome instrument that measures pain and physical activity related to knee osteoarthritis. The purpose of this study is to evaluate, construct validity and consistent reliability of the Persian version of the OKS. METHODS The case series consisted of 80 patients who were clinically diagnosed with having knee osteoarthritis. A...

A CAPTCHA which humans find to be highly legible and which is designed to resist automatic character–segmentation attacks is described. As first detailed in [BR05], these ‘ScatterType’ challenges are images of machine-print text whose characters have been pseudorandomly cut into pieces which have then been forced to drift apart. This scattering is designed to repel automatic segmentthen-recogni...

Most of current text-based CAPTCHAs have been shown to be easily breakable. In this work, we present two novel 3D CAPTCHA designs, which are more secure than current 2D text CAPTCHAs, against automated attacks. Our approach is to display CAPTCHA characters onto 3D objects to improve security. We exploit difficulty for machines in rotating 3D objects to find a correct view point and in further r...

A CAPTCHA is a Completely Automated Public Test to tell Computers and Humans Apart. Typical CAPTCHAs present a challenge string consisting of a visually distorted sequence of letters and perhaps numbers, which in theory only a human can read. Attackers of CAPTCHAs have two primary points of leverage: Optical Character Recognition (OCR) can identify some characters, while nonuniform probabilitie...