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ASP.NET MVC 2 Cookbook by Richard Kimber, Andrew Siemer

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Creating a CAPTCHA system

We have been discussing the ability to return images directly from an action quite a bit. It wouldn't seem right if we had all these discussions and didn't quickly demonstrate how to implement a CAPTCHA system. CAPTCHA is defined as Completely Automated Public Turing test to tell Computers and Humans Apart. It is basically a simple challenge and response system to ensure that your system is not interacting with someone else's system when you are expected to be interacting with a human.

Getting ready

We are going to work off of the knowledge that we covered in the previous examples. No external requirements—just more code!

How to do it...

  1. The first most important part to building anything CAPTCHA-related is to have something ...

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