On Wed, May 18, 2005 at 11:49:07AM -0600, Robert Johnston wrote: > <snip /> > > Would it be possible for someone to, say, sign the NDA, and write a > Closed Source/Binary-Only "Input plugin" for MythTV that handles 5C > (Like the MS Exchange connector for Evolution)?
Generally there is a "robustness" requirement on tools with 5C or similar DRM licences. You can't allow untrusted components or software access to the unencrypted video. So it can't be an "input plugin" in an open system. Instead, it would have to be a complex plugin that performed all functions that need access to the video stream, or a set of them. In a prior message I noted what many of those functions are. It would have to output directly to the hardware of the video card (analog only, no DVI) since playback of course needs access to the video. It could not, for example, use an untrusted device driver to output to the video card because that might be a fake driver just copying the frames. This is a problem because NVIDIA doesn't release the specs for high performance driving of their video cards, so we run their proprietary drivers. So they would have to join the game too. Even with all this it's an interesting debate about whether this plugin would meet the robustness tests, since linux allows you to instrument binary code for debugging, and it would not take long for somebody to provide a patch that streams out the clear bytes. For example, for Tivo to meet the requirements of DirecTV, they had to put in a mechanism that checksummed the kernel on booting to make sure it was a signed kernel and root FS from Tivo. People got around this, but with difficulty, and even then the video files on disk are encrypted there. However, this did not cause Tivo to be shut down by DirectTV (one hopes), that happened for other reasons. The Tivo is in a sealed box with a Torx bit, for some reason that helps your robustness even though you can buy those bits anywhere.
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