captcha
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www.mysoftparade.com / blog / 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. I removed from the form captha_question and added new field captcha_token that holds a hash from question, answer, settings.SECRET_KEY , settings.SITE_URL and expires time (1 hour by default).
Improved Mathematical Captcha | My Soft Parade
I had recently purchased a small computer to act as my development server but I also wanted it to act as second desktop machines. I have plenty of experience using Debian as a server, but I decided to try the new distribution from Ubuntu . The install was pretty easy including getting PHP 5.1.2, Apache 2, and MySQL 5 installed using the familiar apt-get command. (I wish they had included php 5.1.4, but this wasn’t a deal breaker) I was dismayed to find that they didn’t have a package for PDO extension (PHP Database Objects). So I installed the PDO via the pecl command:
Defeating Digg’s CAPTCHA
Breaking a Visual CAPTCHA
Summary This is the homepage of the Shape Contexts based approach to break Gimpy, the CAPTCHA test used at Yahoo! to screen out bots. Our method can successfully pass that test 92% of the time. The approach we take uses general purpose algorithms that have been designed for generic object recognition. The same basic ideas have been applied to finding people in images, matching handwritten digits, and recognizing 3D objects.
