On Fri, Jul 03, 2009 at 09:47:20AM -0400, Richard Stallman wrote:
You'd make me happy if I was able to access cable TV signals I have paid for without DRM.I think it is not quite correct to call cable scrambling DRM. DRM restricts the use of data you have a copy of. Cable scrambling prevents you from getting the data if you do not pay for the descrambler; however, as far as I know, once you do have the descrambler, and do get the data, it does not seriously impede your use of the data.
This is not correct (any more). With the advent of CI+ for DVB (the european-originated version of digital TV meanwhile used in several parts of the world), the cable operators have the possibility to only allow descrambling by CI+ capable receivers/descrambling modules. However, to be CI+ compliant, all receivers and descrambling modules have to be certified and have to authenticate against each other to prevent CI+-compliant operation if this authentication fails. This is necessary because the CI+ specification mandates that any receiver operating a CI+ descrambling module honors the operator-sent bits specifying what you are allowed to do with the "descrambled" signal: analog/digital outputs, store on a disk (the time to stay there can be limited by the operator), and so on.
Needless to mention that you have to prove secure boot to get CI+ certification (and thus a valid certificate).
There's much more to this, but I hope you get the idea.
Regards, Wolfgang