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Israel Researchers Inventing ‘Gotcha’ for ‘Captcha’

Tel Aviv Univ. scientists have come up with a new mechanism that may outsmart spammers who break though “captcha” wavy letter systems on websites.
By Tzvi Ben Gedalyahu
First Publish: 12/30/2009, 3:06 PM / Last Update: 12/30/2009, 3:47 PM

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Tel Aviv University scientists are developing a new security mechanism that may outsmart spammers who break through the wavy letter “captcha” codes that Internet users have to manually type in on websites. The term "captcha" is based on the word “capture” and is a contrived acronym for "Completely Automated Public Turning test to tell Computers and Humans Apart."  

A research project led by Tel Aviv University Professor Danny Cohen-Or demonstrates how a new kind of video captcha code, still in the research stage, may be harder to outsmart.  

“Humans…can see what’s called an ‘emergence image’ ― an object on a computer screen that becomes recognizable only when it’s moving ― and identify this image in a matter of seconds.” he explained. His technique is designed to allow security developers to generate an infinite number of moving “emergence” images that will be virtually impossible for any computer algorithm to decode.

The researchers are also developing methods of automatically generating “hidden” images in a natural background, like a pastoral mountain setting ― a digital “Where’s Waldo?” game. “We’re trying to hide images like eagles or a lion in mountainscape,” says Prof. Cohen-Or. Because the moving image blends into a static background, it’s hard for bots [web robots] to understand what the human eye perceives with only minimal training.

“This could be a tough thing for a robot to crack, so we’re working hard to make it practical,” he emphasizes. “A good captcha has to be something that’s easy for people but hard for a machine.”