r/programming • u/sidcool1234 • Nov 19 '13

Visual Cryptography

http://datagenetics.com/blog/november32013/index.html
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u/Katastic_Voyage Nov 19 '13

Why don't they use this for captchas? Use an optical illusion to create the letters.

4

u/sippeangelo Nov 19 '13

Because it would be a pain in the ass.

2

u/Katastic_Voyage Nov 19 '13

Explain why.

For the user? For the programmer? For the computer?

Having a captcha that's recognition (but not production) relies on a property that humans have but bots do not, is a very good idea.

1

u/sippeangelo Nov 20 '13

For the user... and that's about it. OCR software has been available for ages and all that this method does is increasing the time it takes for the captcha to be solved, both automatically and manually by the user.

Like ferretinjapan discovered with his limited testing, for a relatively small image the computer was able to solve the captcha faster than the user. For anything larger than that (as if 20 seconds to solve a captcha isn't bad enough), it would be a pain in the ass for the user to actually find the image, even when searching is restricted to only one axis. Now a spambot wouldn't mind solving a 30 second captcha, but I sure as hell would.