CAPTCHA (capture) is a type test Challenge / Response in a kind of, to be used to ensure that the responder is not a computer. CAPTCA is the most widely used as a method to verify that the user is human, and difficult to recognize in human beings on the other hand.
There are many different CAPTHA, Most of them are boring but “Catcha” is a unique and simple technique.
Approach is simple: just choose an image of the “cat” in the three images.
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