This article published at MWCS in 2005, by H.S. Cruickshank, M.P. Howarth, S. Iyengar and Z. Sun, propose to replace the current DVB (Digital Video Broadcasting) conditional access (CA) by an IP multicast system. DVB is the standard used for TV satellite. Conditional access is the mechanism used in satellite television to restrict the diffusion to authorized customers. Because the signal is broadcasted to everyone with no control, it rely on cryptographic means to do so. There is many CA systems available such as Viaccess, Connax or Nagravision.
I was interested in this article because it provides a concret and overview of how DVB work and in particular how CA is enforced. As far as I know this is one of the only paper that present DVB scheme in great details. It is far more usable that the Wikipedia page for instance. If you are curious of DVB and satellite in general this is a nice introduction article.
Concerning the multicast protocol replacement, I am not convinced because the strength of DVB is its ability to work without decoder feedback. If this introduce security problems on the other hand it makes it usable everywhere in the world.
Please note that some information about the cryptographic algorithm are inaccurate. For instance Viaccess used AES or RC6 for encryption and not triple DES. EMM are also cycled very often on some CA systems, TPS cycle at least two time by hour for instance, to prevents rogue cards.
Two under looked security gaps of DVB are:
- The ability to performs replay attacks on Smart card
- The card sharing technique that use Internet to share EMM faster that they cycle. (look for Gbox in Google if your are interested in practical uses)
In conclusion this work is valuable as it provides a reference paper about DVB system that can be used as starting point.
Detailed information (5W-H report)
- What: It is as a paper about DVB system conditional access
- Why: DVB CA is problematic because it requires that the receiver does not answer. This leads to security problems. This paper is valuable as it provides a reference on how DVB work. There is very few documentation about the subject.
- Who: H.S. Cruickshank, M.P. Howarth, S. Iyengar and Z. Sun from the Networks Research Group in the Centre for Communication Systems Research, part of the Department of Electronic Engineering at the University of Surrey
- Where: The paper was publish in the 14th IST Mobile and Wireless Communications Summit in Germany
- When: June 2005
- How: The DVB system is depicted by a textual explanation along with nice diagrams.
Additional resources
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