0-9 arası sayıları kullanarak random olarak 2 sayı seçer ve yine random olarak toplama ya da çarpma yaparak sonucu verir.

A simple and custom captcha for Rails3.

Google reCaptcha helpers and verifier

anti-captcha is a Ruby library for recognize captcha on anti-captcha.com

Implements view helpers for the ASIRRA CAPTCHA system for Rails-based websites

you will get arithmatic sum with answer you just have to compare with ur user in controller

Submit captcha images and retrieve the text as a string.

Captcha Gem for Rails, which generates captcha image by Rust.

Rails mountable engine, that provides captcha support

Simple negative captcha for Rails

Implementation of captcha (Completely Automated Public Turing-Test to Tell Computers and Humans Apart) that is both easy to use and easy to customize/extend.

Description of TinyCaptcha.

Generates and verifies ascii art captcha.

Simple negative captcha for Rails

API to interact with BrandCAPTCHA http://www.pontamedia.com/en/brandcaptcha/

This gem enable to use Captchme. Anti spam, Monetize captcha and Audience qualification

dongsx

IQ, Math Captcha