[mythtv-users] Failed Firewire recording

Mark Knecht markknecht at gmail.com
Sat Jun 20 15:44:28 UTC 2009

On Sat, Jun 20, 2009 at 8:18 AM, Preston
Crow<pc-mythtv08a at crowcastle.net> wrote:
> On Sat, 2009-06-20 at 10:38 -0400, Jarod Wilson wrote:
>> > So, why would 1 channel work and the other one not?  Could it be
>> the
>> > 5C encryption?
>> Yes.
> In theory, shouldn't Myth be able to record the encrypted program?  Not
> that it would do us any good.  Or at least detect that there's a stream,
> but it's encrypted, so as to give a more friendly failure message?
> Too bad the 5C specs aren't public.  Perhaps the cable box doesn't even
> acknowledge that there's a stream until it's been authenticated.  Anyone
> know?

If the device at the receiving end doesn't correctly handle passing of
encryption/decryption keys then the transmitting device is allowed to
stop transmitting data completely. New keys are transmitted as often
as every 30 seconds IIRC and the receiver must respond correctly or
the transmitting device is allowed to stop transmitting. Additionally
the transmitting device is allowed to keep a list of known or suspect
receiving devices and not transmit any data to those devices should it
choose that it the right thing to do.

The 5C specs weren't *that* hard to get your hands on some time back.
Don't know about now. All you had to do was attend some working group
meetings. It was the encryption algorithm that was only provided under
a deep, specific NDA to companies that were going to actually
implement something.

Hope this help,

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