How do I verify Android In-app Billing with a server with Ruby?

Question

I am having trouble figuring out how to verify Androind In-app Billing purchases with my Ruby on Rails server.

http://developer.android.com/guide/market/billing/billing_integrate.html

I think that Android gives a Security.java that has some sort of method to verify on physical device. From my research it seems like either (1) I need to figure out how to use this Security.java class with my Ruby on Rails server or (2) I need to port Security.java to Ruby.

Is this correct? Does anyone know another way to verify the receipt?