TELECOM Digest OnLine - Sorted: Re: Satellite Radio Authorization: How Does it Work?

Re: Satellite Radio Authorization: How Does it Work?

Mark Crispin (MRC@CAC.Washington.EDU)
Fri, 11 Feb 2005 18:06:18 -0800

On Fri, 11 Feb 2005, AES wrote:

> When a satellite authorizes a given radio, does it do it by sending
> that radio (and, as a side effect, all other radios) some kind of
> digital key that combines with some unique built-in matching key in
> that particular radio to enable it to decode the broadcast content?

Correct.

> If so, presumably if you stop paying your bill it can also deauthorize
> your radio by sending something to wipe out the code?

I believe this to be the case. It's certainly the way that satellite
TV works.

> But suppose you put your radio in a shielded box, stop paying, wait a
> few months until they give up trying to deauthorize you, then bring it
> back out -- are you still authorized? Or does every authorized radio
> have to get reauthorized at some periodic interval?

Maybe, and yes.

A satellite radio or TV that was not receiving when the update comes
down continues with its old status. But, it doesn't last for more
than a few minutes, when the satellite company's periodic re-update
hits the receiver.

If the receiver has had no power (as in unplugged, not "turned off",
since it's still receiving updates even when "turned off") for an
extended period of time, it drops its authorization entirely and goes
into unauthorized mode. It stays in that mode until the next periodic
re-update when it goes alive again. RVers with satellite receivers
who are quite familiar with this behavior.

In my experience, it only stays unauthorized for a couple of minutes
before it comes back.

Empirical evidence suggests that every receiver is updated every few
minutes. You can also call and ask for a manual update if you're
having problems.

There is quite a tribe of individuals who hack the security of
satellite TV, usually in modifying the access cards to be promiscuous;
and an equal tribe at the satellite TV companies who figure out how
the hack worked and (1) develop a new generation of cards that breaks
the hacks, (2) develop a counter-hack that attacks hacked cards and
disables them. These access cards are actually programmable CPUs --
they're not just passive memory -- and the actual work is done there.
I don't think that the receivers are anything other than receivers; I
don't think that they have a crypto engine.

North American satellite TV pirates seem to be primarily in Canada,
and focus their attacks at US satellite providers. Apparently, there
are some Canadians who want to get the TV that their socialist
government denies them.

I haven't heard of anyone hacking satellite radio. I suspect that it
isn't economical; also the receiver itself would have to be hacked
instead of a card.

> Bottom line: Do individual radios actually talk back to the satellites
> at any point?

No.

> Or do authorization and other command signals flow only from the
> satellites to the radio?

Yes.

-- Mark --

http://staff.washington.edu/mrc
Science does not emerge from voting, party politics, or public debate.
Si vis pacem, para bellum.

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