Captcha in GWT Widget

Question

I'm looking for a Captcha (SimpleCaptcha or JCaptcha) widget for GWT. I've found examples online, but they all use servlets to generate and validate the Captcha. Are there any client-only Captcha implementations?

Answer 1

A CAPTCHA has to be generated server-side because of the implicit security. There's no way to be positive that anything client-side is secure. Since GWT client code gets turned into Javascript, it's feasible that it can be modified. Potential for modification means potentially insecure content. That's why implementations like this all use server-side code to generate, pass down as an image, and validate all CAPTCHAs.