Re: [Discuss-gnuradio] USRP2 + WBX for DVB-T replaying

[Marcus Müller]

Hi Dino,

DVB-T works in the UHF / VHF frequency bands, something you can tune
your wbx at without problems.
Bandwidth is about 8MHz (if I'm not mistaken), so that's low enough.
Since it sounds like you'll be doing stuff offline (not in realtime),
processing power is not a factor for your problem, either.

DVB-T generally uses OFDM with large numbers of bins (2^11 or 2^13-bin 
fft), generous guard intervals and whatnot. A moderately complex system, 
but someone has already implemented a dvb-t modulator in GNU Radio[1], 
you can take a look at that, but I doubt it would work with current 
versions of GNU Radio.

Regarding to your EMM "hint": You do have to realize that EMMs are 
rather "high level" concepts; you need to encode them into a data 
stream, mux them together with the video stream, encode that whole 
thing, map it to the correct OFDM carriers and transmit that.
Since what we're talking about are messages meant to inform decryption
devices about their working state, I guess it won't be as easy as 
replaying EMMs you captured, since it most probably carries keys for 
specific content. Then, on the other hand, TV encryption in the 90s has 
gained notority for being broken shortly after deployment, so this is 
actually an interesting field of research for someone with a 
cryptographic background (which I can't claim to have).

Happy hacking

Marcus


[1] PELLEGRINI, Vincenzo; BACCI, Giacomo; LUISE, Marco. Soft-dvb: A 
fully-software gnuradio-based etsi dvb-t modulator. Proc. WSR, 2008, 8. Jg.
Am 03.05.2013 23:35, schrieb Dinos Pastos:
> Hi there,
>
> I have a USRP2 with WBX board which has been sitting around doing nothing.
> I was wondering if it is possible to use this hardware to get a live
> DVB-T signal and replay it back.
>
> What I want to do is to intercept entitlement management messages and
> modify/remove them on the fly.
>
> Please let me know if there is such support with this hardware or even a
> previous project that tackles this request.
>
> Regards
>
> Dino
>
>
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