[mythtv] [PATCH] Enable recording of encrypted channels withoutdecrypting them first.

Allan Stirling dibblah.allan.stirling at googlemail.com
Fri Jul 16 14:34:50 UTC 2010

wf_myth_user at online.nl wrote:

> But when the file is stored encrypted only people who have access to a cam
> with smartcard can watch the file.
> So for legal reasons option(2) would be the better solution.
> When looking at it this way it would even make sense to move the cam and
> smartcard to the frontend.

I'm not quite sure why all of this started but it's 
essentially impractical to do "offline" decrypting for a 
number of reasons:

1. There are no interfaces to hardware CAMs that are 
supported in Linux that allow arbitrary data to be passed to 
them. DVB cards take data from the demodulator and switch it 
either through the CAM or directly to the bridge chip. Very 
few video bridge chips have outputs and none that I have 
seen pass the output to the CAM, since it would have no 
purpose in a "normal" system. The Hauppauge standalone USB 
CAM is not supported under Linux.

2. Keys change. This means that your recordings are only 
"valid" and decryptable at the time when they are recorded. 
Manufacturer PVRs get over this in a number of ways which 
are not possible for us since we do not have access to the 
internals of the CAM.

There are other reasons why this should not be in the 
frontend, but these are the primary ones.

An open interface on the backend for the Hauppauge CAM may 
not be a terrible idea, though - It may even spur on 
development of the Linux driver.



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