A smart captcha library

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

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.

RedisCaptcha provides simple captcha that can be read by human.

Merb plugin that provides resource access rate limits and captcha'ing

Captcha based on encyrpting and decrypting user data by mathematical operation

Helps humankind with simpler captchas

Simple captcha image generator gem

Death by Captcha Ruby implementation (HTTP API)

NO LONGER MAINTAINED AND NOT RECOMMENDED, AS BOTS ARE ABLE TO RESOLVE CAPTCHAS BETTER THAN HUMANS. Based on Login Attempts check if captcha is necessary. It stores a permanent cookie and uses a table for tracking login requests.

Integrate the AreYouAHuman.com CAPTCHA alternative human verification into your Ruby/Rails application

This library can help you create a captcha in your terminal application, which may be damaged by a large influx of requests.

Quick little arithmetic plain-text captcha

Simple, easy captcha for Sinatra

Gem that uses RuCaptcha API to solver any type of captcha

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

Merb plugin that provides resource access rate limits and captcha'ing

Repackaged visualCaptcha's backend service, including translation and minor modification. Mainly for private use. Everything still belongs to original author: emotionLoop.

Forked from https://github.com/kares/simple_captcha

Form protection with simple captcha calculations.