A Google-style captcha for enterprise Rails apps

• Batch generate captchas
• Use ciphered filenames (no need to store filename/captcha pairs)
• Easy configuration
  • Number of captchas
  • Period for captcha refresh
  • Colors, wave, implode
• Handle lots of users

Tested with Ruby 1.8.6, 1.8.7, and 1.9.1.

script/plugin install git://github.com/winton/captcha.git

Captcha::Config.new(
  # Used for filename cipher
  :password => 'something-unique',
  # Captcha colors
  :colors => {
    :background => '#FFFFFF',
    :font => '#080288'
  },
  # Number of captcha images to generate
  :count => RAILS_ENV == 'production' ? 500 : 10,
  # Where to write captchas
  :destination => "#{RAILS_ROOT}/public/images/captchas",
  # Generate new batch every day
  :generate_every => 24 * 60 * 60
)

See lib/captcha/config.rb for more options.

class ApplicationController < ActionController::Base
  acts_as_captcha
end

You may now use the reset_captcha method in any controller.

class User < ActiveRecord::Base
  acts_as_captcha :base => "base error when captcha fails", :field => "field error when captcha fails"
end

With no parameters, a default error is added to the "captcha" field (:field => true).

Specify :base => true to use a default error for base.

<img src="/images/captchas/<%= session[:captcha] %>.jpg" />
<%= text_field_tag(:captcha) %>

user = User.new
user.known_captcha = session[:captcha]
user.captcha = params[:captcha]
user.save
reset_captcha

0 0 * * * cd /path/to/rails/app && /usr/bin/rake RAILS_ENV=production captcha:generate

Your config file sets the captcha refresh period. The rake task just checks if its time to repopulate, and does so if necessary.