I'm curious, can someone provide a simple several paragraph, basic explanation of how satellite radio authentication works? eg. If the radio is only a receiver and I cancel my subscription how does the radio know that the subscription has been canceled (do they send it a list of all valid radios)?
They probably send out programming information occasionally to tell your radio to ignore them... "number 102374 has not paid its bill, it should stop listening, be a good boy". The radio probably then deletes some kind of decryption key it has stored.
Here are seemingly better informed guesses from Wikipedia:
`Each receiver has an Electronic Serial Number (ESN) Radio ID to identify it. When a unit is activated with a subscription, an authorization code is sent in the digital stream telling the receiver to allow access to the blocked channels. Most services have at least one "free to air" or "in the clear" (ITC) channel as a test. For example, Sirius uses channel 184, Sirius Weather & Emergency.'