CAPTCHAWhat is CAPTCHA?Types of CAPTCHAsVisual-based CAPTCHAsSlide 5Further InformationCAPTCHAPresentation byAnnette Tsui, Section 2What is CAPTCHA?CAPTCHA: Completely Automated Public Turing test to tell Computers and Humans ApartIntroduced by Alan Turing in 1950 - “If a computer’s performance was indistinguishable from a human, it could be deemed intelligent.”Still not able to do completely, but programs have been developed that are able to pass tests that humans can passTypes of CAPTCHAsVisual-based and Sound-basedVisual-based examples:Gimpy, EZ-Gimpy, Gimpy-r, Pessimal Print, BaffletextSound based: Sounds CAPTCHA used in Hotmail®, Yahoo! ®, and Altavista® new login accountsVisual-based CAPTCHAsYahoo!® CAPTCHA (EZ-Gimpy)Gimpy CAPTCHASource: http://www.captcha.netVisual-based CAPTCHAsPessimal Print CAPTCHABaffletext CAPTCHASource: http://www2.parc.com/istl/projects/captcha/captchas.htmFurther InformationThe CAPTCHA Project: http://www.captcha.netPARC (Palo Alto Research Center) website about CAPTCHAs: http://www.parc.xerox.com/research/istl/projects/captcha/Greg Mori’s web page about his attack on Gimpy:
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