CAPTCHA IF YOU CAN

A CAPTCHA (Completely Automated Public Turing Test to tell Computers and Humans Apart) is a type of challengeresponse test used in computing to determine whether or not the user is human. Several people claim to have invented the concept. Late 1990s patent applications describe using human skills and cognitive abilities to solve simple problems that would be very difficult for computers. It’s around 2003, though, in the work of Von Ahn and his colleagues, that the term Captcha is said to be first found. It became the standard form of identity authentication for thwarting large-scale online abuse by automated programs, or bots.

“By about 2005, I did a back of the envelope calculation that, about 200 million times a day, somebody typed a CAPTCHA,” says Von Ahn.

The concept wasn’t perfect, of course. “It takes perhaps 10 seconds of your time. That works out to 500 000 hours a day wasted.”

This led to the development of RECAPTCHA. You still spent the 10 seconds, but now there was a purpose: the data generated by typing out the authentication image was helping describing images and decipher documents.