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...

To speak fluently is a complex skill. If reaching this goal in one’s mother tongue is already quite a feat, to do so in a foreign language can be overwhelming. One way to overcome the expression problem when going abroad is to use a dictionary or a phrasebook. While neither of them ensures fluency, both of them are useful translation tools. Yet, neither can teach you to speak. We will show here...

We report the synthesis and preliminary characterization of "clickable" inhibitors of human transglutaminase 2 (TG2). These inhibitors possess the 3-halo-4,5-dihydroisoxazole warhead along with bioorthogonal groups such as azide or alkyne moieties that enable subsequent covalent modification with fluorophores. Their mechanism for inhibition of TG2 is based on halide displacement, resulting in t...

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...