Monday, May 25, 2009

New Puzzles That Tell Humans From Machines | | Star-News | Wilmington, NC

New Puzzles That Tell Humans From Machines | | Star-News | Wilmington, NC:

Researchers at Google are testing a new captcha that requires people to turn upright randomly rotated images, like that of a parrot perched temporarily upside-down on a leafy branch. The task is a breeze for people — using a cellphone touchscreen, for example, to flip the image — but hard for machines.
Another new approach in the captcha arms race was developed by Luis von Ahn, a professor at Carnegie Mellon University and a pioneer in captcha development. Dr. von Ahn has created a more secure version of audio captchas used by the visually impaired in surfing the Internet with screen readers.

In the new captchas, which Dr. von Ahn said had proved to be more secure in research trials, the audio clips are not of numbers, but of phrases drawn from old radio shows posted on the Internet Archive. They will be easy for people to solve, but tough for automated programs.

Dr. von Ahn has also created a free system, called reCaptcha (, now used by about 120,000 sites including Ticketmaster, Craigslist, Facebook, Twitter and The New York Times.


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