[linux-dvb] Re: TT-budget+ Smart card reader + PIII 700?

[Giuseppe La Rosa <larosa@euro2001.com>]

> Hi,
>
> Giuseppe La Rosa writes:
>  > Preamble: I don't have a DVB-s card, i follow this list by many months
>  >
>  > I don't know how exactly is the TT-budget but i think that it has at
least
>  > the VES1893 chip, i guess.
>  > I'have found here
>  > http://www.semiconductors.philips.com/acrobat/other/cms/ves1893.pdf
>  > that in this chip there is a DVB descrambler.
>  > If this is right, and it really implements the DVB Common scrambling
>  > algorithm, it could be used to implement simple, public available, CA
system
>  > such as the 'Remotely Keyed Encryption Schemes' of cryptolabs. What is
>  > missing is to manage the ECM and EMM of this CA system, but i this that
this
>  > could be done in software.
>
>
> Yes, it has a DVB descrambler built-in.
> No, it does not have a DVB Common Scrambling Algorithm built-in.
>
> The "DVB descrambler" built into the VES1893 (and all other DVB
> decoders) refers to the energy dispersal process which is part of the
> DVB standard.
> To avoid long series of 0s and 1s in the signal, which could lead to
> unwanted interference effects, the DVB stream is pseudo-randomized for
> broadcast. This could be described as scrambling with a publically
> known key.
>
> This energy dispersal scrambling/descrambling has NOTHING to do with
> the Common Scrambling Algorithm.
> Please look it up in ETS 300 421, section 4.4.1
> "Transport multiplex adaptation and randomization for energy dispersal"
> where you will find a diagram of the scrambling algorithm.
>
> The VES1893 basically implements all of ETS 300 421 after the
> actual reception of the signal (which is done by the rest of the
> tuner), nothing more, nothing less.
>
>
> The Common Scrambling Algorithm (CSA) is usually built into the
> demultiplexer, i.e. in parts of the AV7110 in case of the non-budget
> card, or into CI-CAMs.

So, it could be possible to implements simple CA systems in the non-budget
cards using this functionality of the AV7110? Cause I've noted in the
dvb_demux.c this:

        if (dvbdmxfeed->descramble)
                return -ENOSYS;

and I deduced that this functionality wasn't available in the demux. So I've
tried elsewhere in the VES1893, and I've made the mistake that you
explained.
What does it means? That the functionality is present but is not used in the
driver implementation?
Do you think that could be activated? What I think is that, if is present,
should not be difficult to activate and use it. Form the demux part, it must
be only written the functions to tell what control words have to be used.
The rest is to make some software that implements the CA System part that
manage ECM and EMM.


> Since the budget card does not have a hardware demultiplexer this
> would have to be done in software. They only give the CSA specs to
> hardware companies though. Looks like they are not as stupid as the DVD
> people ...
>
>
> Alternatively, one could connect a PCMCIA interface to the PC, plug
> in a CI-CAM (+ official smartcard and payed subscription course)
> and somewhow pass the transport stream through it.
> If you look at the PIN descriptions of the CI-CAMS you will notice
> that you will have to clock the bytes through the CI-CAM "by hand",
> i.e. you will have to set and poll the data valid and other status
> pins in software.
> Have fun!
>
>
> Ralph
>
>
>
>
>
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>



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