Efforts to defend against automated attacks on e-commerce services have led to a new security protocol known as a CAPTCHA, a challenge designed to exploit gaps in the perceptual abilities between humans and machines. In this paper, we propose a new paradigm for building CAPTCHA’s which offers simultaneous benefits to both online security and pattern recognition research. We illustrate our discu...

Nowadays, many daily human activities such as education, trade, talks, etc are done by using the Internet. In such things as registration on Internet web sites, hackers write programs to make automatic false registration that waste the resources of the web sites while it may also stop it from functioning. Therefore, human users should be distinguished from computer programs. To this end, this p...

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...

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...

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...