chris at carde
Sep 12, 2003, 12:11 PM
Post #5 of 6
(2543 views)
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RE: OT: FCC adopts 'plug and play' cable for TVs
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Hello,
I believe the standard being proposed is "OpenCable"
(http://www.opencable.cm/). I had an interesting email exchange with
some of the people involved in OpenCable regarding the hypothetical
viability of an open-source OpenCable implementation. There are some
interesting issues that, as far as I can tell, would prevent any open
source implementation from succeeding. First, let me relay some of the
more interesting points I've learned. This information is all available
in the specifications and other documents on OpenCable's site:
- OpenCable not only specifies the modulation, encoding, and encryption
standards for interoperable digital (and HDTV) cable services. It also
defines a software platform to deliver software services to the user
terminal. These services could take the form of a traditional on-screen
program guide or could implement "next generation" interactive
television. It's up to the imagination of those implementing a
particular system.
- As mentioned earlier, access control for user terminals will take the
form of Point-Of-Deployment (POD) modules. These PODs will likely come
in the form of smart cards or PCMCIA form-factor devices. The POD will
interact with the cable head-end to selectively authorize and decrypt
services to which the user subscribes.
Conventional wisdom suggests that one could take the specification and
build an open implementation around that would interoperate with the
cable company's proprietary POD and everyone would be happy.
Unfortunately, that's not the case. The industry is not only concerned
with unauthorized persons obtaining access to pay channels -- they're
also concerned with people having the capability to record this content
in the digital domain and redistribute it. Consequently, they've
essentially built the system to tightly control who can make POD
"hosts". The POD will use cryptographic signatures to authenticate to
the host device when it is inserted. Reverse-engineering secret keys
from existing hardware manufacturers will not necessarily be worthwhile,
as certificates can be revoked at the cable head end. Furthermore, the
POD and host module will negotiate symmetric encryption of certain video
content to transmit between the POD and host module to avoid the
possibility of a man-in-the-middle attack intercepting and recording the
MPEG program stream.
The OpenCable licensing agreements require that any licensee must make
guarantees and demonstrate that their system is reasonably resistant to
tampering, video extraction, and reverse-engineering of the keys. Only
then will keys be released and assigned to a manufacturer.
Please forgive me if I've made any egregious errors here. It's been a
month or two since I read the specs and this is just what I remember.
For further reading, take a look at these links:
OpenCable Security Specification
http://www.opencable.com/downloads/specs/OC-SP-SEC-I02-030707.pdf
Copy Protection in Digital Cable Systems
http://www.opencable.com/downloads/BrobergNCTA2001.pdf
POD-Host Interface License Agreement
http://www.opencable.com/downloads/PHILA_080103.pdf
Getting on my soapbox for a minute, it's a darned shame that things had
to come to this. From a purely technological perspective, this
specification could have lead to an industry-leading open-source
implementation of a Linux-based cable television terminal / PVR. But yet
again, due to DRM issues, the field will yet again be limited to major
commercial players.
Chris
---------
Christopher Carde
Graduate Researcher, FutureTruck
UC Davis Hybrid Electric Vehicle Center
(530) 752-8849 http://www.team-fate.net/
-----Original Message-----
From: mythtv-users-bounces [at] mythtv
[mailto:mythtv-users-bounces [at] mythtv] On Behalf Of Joseph A. Caputo
Sent: Thursday, September 11, 2003 1:22 PM
To: Discussion about mythtv
Subject: RE: [mythtv-users] OT: FCC adopts 'plug and play' cable for TVs
> -----Original Message-----
> From: mythtv-users-bounces [at] mythtv
> [mailto:mythtv-users-bounces [at] mythtv]On Behalf Of
> linux [at] keithandjill
> Sent: Thursday, September 11, 2003 3:45 PM
> To: Discussion about mythtv
> Subject: Re: [mythtv-users] OT: FCC adopts 'plug and play' cable for
TVs
>
>
> Look for DMCA lawsuits against the first person who
> reverse-engineers the encryption cards to
> allow Linux boxes access to content. Just like DeCSS and DVDs.
Not necessarily; it really wouldn't require any reverse engineering. If
TV
manufacturers can use the technology, then so can TV-tuner card
manufacturers. All it requires is for somebody like Hauppauge to come
to
market with a tuner card that has a socket for the 'decryption card'
from
your cable provider. You'd still need to *get* the card from your cable
provider; you'd just be plugging it into a PCI adapter instead of your
TV.
All you'd need on the Linux side would be a driver for the new card.
Now, if someone reverse-engineered the decrypter card so that you didn't
need it (i.e., replaced it with a software library), then yeah, that
would
run afoul of the DMCA.
-JAC
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