The acts_as_authentic method has a crypto_provider option. This allows you to use any type of encryption you like. Just create a class with a class level encrypt and matches? method. See example below.

Example

  class MyAwesomeEncryptionMethod
    def self.encrypt(*tokens)
      # The tokens passed will be an array of objects, what type of object
      # is irrelevant, just do what you need to do with them and return a
      # single encrypted string. For example, you will most likely join all
      # of the objects into a single string and then encrypt that string.
    end

    def self.matches?(crypted, *tokens)
      # Return true if the crypted string matches the tokens. Depending on
      # your algorithm you might decrypt the string then compare it to the
      # token, or you might encrypt the tokens and make sure it matches the
      # crypted string, its up to you.
    end
  end