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

[Michael T. Dean]

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.

Mike