如何使Rails中的模型id不可预测和随机

I'm writing a rails app that, by its nature, CANNOT require users to register, and thus cannot use authentication as the usual means to protect records. (I know, I know...) User information here is limited to email addresses. So I do need a way to make my model IDs unpredictable so that other IDs cannot be easily guessed. (I know, I know...)I'm writing a rails app that, by its nature, CA