simple encrypted fields in rails

encrypter.rb

# extend Encrypter::Encryptable
# encrypt :email, :password

class Encrypter
  def self.encrypt val
    encrypter.encrypt val
  end

  def self.decrypt val
    encrypter.decrypt val
  end

  module Encryptable
    def self.extended base
      def base.encrypt *fields
        fields.each do |field|
          define_method "#{field}_with_decryption" do
            Encrypter.decrypt self.send("#{field}_without_decryption")
          end
          alias_method_chain field, :decryption

          define_method "#{field}_with_encryption=" do |val|
            self.send "#{field}_without_encryption=", Encrypter.encrypt(val)
          end
          alias_method_chain "#{field}=", :encryption
        end
      end
    end
  end

  private
  def self.encrypter
    @@encrypter ||= ActiveSupport::MessageEncryptor.new(ActionController::Base.session_options[:secret])
  end
end