Improved Mathematical Captcha
A week ago I published MathCaptchaForm that I use in my blog for preventing spam. Malcolm Tredinnick and then other people noticed that solution don't protect from replay attacks and once solved question can be used by spam bots on different web-sites. So I added protection against replay attacks and implemented it without database usage. It was original requirement to keep MathCaptchaForm as lightweight as possible.
Mathematical Captcha
When spam bots started to post comments in my blog every day I realized that I need some kind of simple anti-spam protection. I didn't saw yet real anti-spam AI and don't like image captchas. I looked for a mathematical captcha where human is asked to solve a simple mathematical calculation like 3+5=?. Unfortunately I didn't found open-source implementation and write own MathCaptchaForm. A week already I don't see spam posts.
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