Well, maybe they are happy with that. But it seems it is vulnerable to replay attacks. For instance if I have box 1234 with options "all" it seems I could give it "1234 all" even after I canceled service, assuming I could send signals to it. Do they assume I can't? Good authentication usually involves showing you can respond to some random number in such a way that it proves you have secret information yet does not divulge that secret. Lots of services have used lots of different methods over the years. Most can be bypassed. It keeps evolving so just because something has been used commercially doesn't mean everybody would be satisfied with it today. - Tom John Shutt wrote: > You don't need a backchannel for authentication. You only "need" a > backchannel for impulse pay-per-view. > > Remember USDTV? > > Cable, DBS, and USDTV all work the same way: The provider transmits a > continuous stream of authorized box serial numbers, and what services > each is authorized to decode. If your box falls off the list, your > box will go dark. > > This is the same system as the very first scrambling method, > VideoCipher, which was used to thwart backyard satellite dish owners. > > John > > ----- Original Message ----- From: "Tom Barry" <trbarry@xxxxxxxxxxx> > >> Thanks. I had not previously read those documents. And I suppose that >> any scheme for multicast security like that could indeed be adapted to >> broadcast as long as they had a small back channel for authentication. > > > > ---------------------------------------------------------------------- > You can UNSUBSCRIBE from the OpenDTV list in two ways: > > - Using the UNSUBSCRIBE command in your user configuration settings at > FreeLists.org > - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word > unsubscribe in the subject line. > > ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.