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Main Web>TWikiUsers>ElaineFarrow>RobotsBrainsArtificialIntelligence>LearningAndVision (24 Aug 2009, ElaineFarrow) (raw view)EditAttach

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A CAPTCHA is a program that can tell whether its user is a human or a computer. You've probably seen them — colorful images with distorted text at the bottom of Web registration forms. CAPTCHAs are used by many websites to prevent abuse from "bots," or automated programs usually written to generate spam. No computer program can read distorted text as well as humans can, so bots cannot navigate sites protected by CAPTCHAs.

Telling Humans and Computers Apart Automatically

A CAPTCHA is a program that can generate and grade tests that humans can pass but current computer programs cannot. For example, humans can read distorted text as the one shown below, but current computer programs can't:
CAPTCHA example

The term CAPTCHA (for Completely Automated Turing Test To Tell Computers and Humans Apart) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University. At the time, they developed the first CAPTCHA to be used by Yahoo.

Recaptcha examples attached.

Attachments

Topic attachments
I	Attachment	Action	Size	Date	Who	Comment
jpg	OCR_low.jpg	manage	33.2 K	24 Aug 2009 - 11:43	ElaineFarrow	OCR result of low quality scan
jpg	OCR_medium.jpg	manage	96.7 K	24 Aug 2009 - 11:44	ElaineFarrow	OCR result of medium quality scan
jpg	scan_low.jpg	manage	86.3 K	24 Aug 2009 - 11:43	ElaineFarrow	low quality scan
jpg	scan_medium.jpg	manage	118.0 K	24 Aug 2009 - 11:44	ElaineFarrow	medium quality scan

Topic revision: r2 - 24 Aug 2009 - 13:58:07 - ElaineFarrow

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