Captcha based on encyrpting and decrypting user data by mathematical operation

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

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.

IQ, Math Captcha

Simple captcha image generator gem

RMagickCaptcha is a gem that implements captcha for using in Rails application.

Solve Media CAPTCHA Replacement

Helps humankind with simpler captchas

Form protection with simple captcha calculations.

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

A very simple rack captcha middleware via captchator.com API

Gem that uses RuCaptcha API to solver any type of captcha

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

HumanDetector is a friendly logic captcha for Rails the doesn't require any external system dependency (e.g. external captcha API connections). It uses a simple question that any 7 or more years old human can understand, but that a spambot will not be able to answer. This Gem supports Ruby v1.9.2...

This is a gem wrapper for tiny captcha in C with no dependencies.

这是一个验证码生成器。基于rucaptcha。本人只是将他的源码拉下来。为我的网站进行适配。因为我不使用sesion.id

Description of RailsCaptcha.

Death by Captcha Ruby implementation (HTTP API)

Simple, easy captcha for Sinatra