Web developers have taken the idea of Captchas - challenge-response systems that are often used to stop the automatic creation of webmail accounts by spammers - forward in a fun way by using images of kittens instead of distorted images of letters. KittenAuth features nine pictures of cute little animals, only three of which are feline. A user demonstrates that there's a human in front of machine by selecting the three kittens among these images.

Doubtless the choice of animal would find favour over at b3ta.com.

Security guru Bruce Schneier also thinks the idea merits further investigation even though it certainly not ready to be applied seriously just yet. For one thing, as the system stands, there's a one in 84 chance of a computer randomly selecting the three correct images.

"You could increase the security by adding more images or requiring the person to choose more images. Another worry - which I didn't see mentioned - is that the computer could brute-force a static database if there are only a small fixed number of actual kittens," he writes.

Despite these reservation, Schneier describes the concept of authentication using pictures of animals in this way as "an interesting idea that warrants more research". ®

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