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Books, Technology

CAPTCHA Gotcha

02.05.07 | 1 Comment

Just read this story (via Digg), about a “reverse CAPTCHA”. For those of you who don’t know, a CAPTCHA is a “Completely Automated Public Turing test to tell Computers and Humans Apart”, and is used on many content management systems to prevent spam. When you post a comment to this blog, the stylized series of letters you have to enter is a CAPTCHA.

This reminded me of a pretty good short story by Fred Saberhagen, one of his “Beserker” series. Background: in the far future, a race of automated spaceships is bent on destroying humanity. In “WHAT DO YOU WANT ME TO DO TO PROVE IM HUMAN STOP”, a human cruiser is pursuing two spaceships heading for a large colony. One of the ships is carrying vital material for the colony’s defense; the other is a Beserker. Blow them both up and the colony will be wide open to attack. Blow up neither and it will be under attack.

There is no audio or video communication, only binary, and the ships are too far away to overhaul and inspect. One claims to be a high-speed courier, the other a lifeboat from a passenger ship heavily damaged in a Beserker attack. So, who to trust?

Saberhagen comes up with a pretty good solution to this problem, based around a simple fact: if machines remember something, they remember it in every detail. People need hints.

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