[mythtv-users] HDCP Key out?

Robert McNamara robert.mcnamara at gmail.com
Tue Sep 14 20:17:51 UTC 2010

On Tue, Sep 14, 2010 at 1:13 PM, Tortise <tortise at paradise.net.nz> wrote:
> ----- Original Message ----- From: "Robert McNamara"
> <robert.mcnamara at gmail.com>
> To: "Discussion about MythTV" <mythtv-users at mythtv.org>
> Sent: Wednesday, September 15, 2010 3:49 AM
> Subject: Re: [mythtv-users] HDCP Key out?
> I for one appreciate your responding Robert, thank you.
> On Tue, Sep 14, 2010 at 8:33 AM, Brian J. Murrell <brian at interlinx.bc.ca>
> wrote:
>> On Tue, 2010-09-14 at 09:13 -0600, Brian Wood wrote:
>>> Thought this might be of interest to folks here:
>>> http://entertainment.slashdot.org/story/10/09/14/1211205/HDCP-Master-Key-Revealed
>> Now, the usual suspects will pop up and say that this sidesteps the
> Image Constraint Token (ICT).
> Not only am I a suspect, as I am responding, I am guilty of the charge of
> seeking to understand.
>> And a more informed someone will mention that the ICT is *only* a part
> of the Blu-ray specification, and that *0* discs ship with it enabled,
> and that it is not relevant in any way to broadcast media.
> I am not so sure that ICT are not a part of some broadcast media, they after
> all mere digital tokens (protocol flag according to
> wikipedia) and there is no reason I can see why they cannot be transmitted
> in a broadcast stream, just as they are embedded in a BR disc stream.

Except they're not.  ICT is part of AACS, not just some MPEG stream
flag.  You'd need to switch the entire infrastructure's encryption to
AACS to use the ICT.  It's just plain not gonna happen (ie, you're not
going to see everyone completely scrap their existing encryption,
broadcast, and receiver equipment to do so).

> As I see it the key to ICT working is a two way information flow, to allow
> the confirmation that there is a display device at the end of the chain that
> is HDCP compliant to send HD to (else SD or nil).  It seems DVB-T is a one
> way stream, so I expect Robert is correct here.
> What about IPTV(or an Internet two way protocol?), where a IPTV broadcaster
> uses a BR ICT enabled disc as the source in HDCP equipment and there is a
> two way digital traffic path?  Seems to me that ICT and HDCP was also
> designed for this?  Doesn't the schema involve a digital chain of any number
> of compatible intermediary devices / interconnects length?

See above, that's not how the ICT works (ie, it's not part of some
tunneled encryption, it's part of a specific encryption method that is
unique to blu-ray and HD-DVD).


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