[mythtv-users] The Coax Straightjacket: Stopping Cable Copy-Protection Abuse

[R. G. Newbury]

Michael T. Dean wrote:
> On 10/12/2007 12:32 PM, R. G. Newbury wrote:
>> This link: http://lauren.vortex.com/archive/000310.html
>>
>> is an interesting article about cableco's changing the 'do not copy byte'.
>>
>> Does anyone know of any programs which would allow a user to find the 
>> CCI byte in a digital stream?
>>
>> I'm in Canada, and the use of a program to find, and even change the CCI 
>> byte in a digital file on my computer is not illegal. And although the 
>> MPAA and RIAA believe otherwise, I do not think that it breaches the US 
>> DMCA, although that is just my opinion, and relies in part upon my 
>> necessarily fuzzy understanding of the US Copyright Act fair use 
>> doctrine, as explained by SCOTUS in the Betamax decision.
> 
> Though this is probably not the right forum for this, I would guess that
> the only time you could change the do-not-copy byte and be able to use
> the video is if you did it on unencrypted video.  However, since
> (most?/all?) available digital capture cards/Linux drivers ignore
> (=aren't designed to work with) any "broadcast flag" (such as the
> do-not-copy byte)--even if it appears on unencrypted video (such as OTA
> video)--you don't need to change that byte.  You can just record the
> unencrypted video.
> 
> In other words, if one were to design the do-not-copy byte such that it
> could be applied to unencrypted video to tell an STB to encrypt the
> data, you could just capture the unencrypted video directly rather than
> through the STB.  Therefore, I would guess that the byte is applied to
> video and then both video and do-not-copy byte are encrypted so that one
> would have to decrypt the video to change the byte.  If you can decrypt
> the video, there's no reason to then change the byte--you might as well
> just capture/decrypt it directly rather than through the STB.
> 
> Then again, dumber mistakes have been made in commercially-implemented
> security, so it's possible that it may have been designed incorrectly. 
> And, since the above is all conjecture, it's quite possible that I'm wrong.
> 
> Interesting link, though.

Yes. Interesting is the right word. It is unclear whether the cablecos 
referred to are adding/changing the do-not-copy byte to unrencrypted 
streams, but that is what I infer is being referred to.

And I can see cablecos doing just that. The 'usual' manner of conduct 
seems to be that premium content is only transmitted as encrypted, but 
the MPAA/RIAA bastards (with apologies to those to whose parents were 
not married...(Yes, I ALWAYS apologize to the US Marines! but I 
digress...)) seem to think that no-one, anywhere should be entitled to 
copy anything sent digitally.

I doubt that the do-not-copy byte would be of much utility in the FOSS 
world, if it were not for its pernicious existance in firmware..for 
example in HDMI/HDCP interfaces.

Geoff