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JPL's Wireless Communication Reference WebsiteChapter: Network Concepts and Standards
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Among the members of the commercially driven Ad-Hoc group, there are various
points of view. There are the broadcasters, who may be classified either as
"established pioneers" or as "newcomers". On one hand, the
pioneers would like make sure that their investment in their operation is worth
every penny and will accept standardization only up to a certain point. On the
other hand, the newcomers, consisting mainly of network operators and the smaller
broadcasters, would like to cooperate, since they know that not many people
would buy a decoder box to watch only one or two channels. Therefore, complete
standardization of the box would really be the solution for them. Finally there
are the equipment manufacturers who wish to standardize to come to cheap mass
production.
The more technically oriented Specialist Group has looked at several scenarios
involving different combinations of scramblers and conditional access systems.
It was quickly agreed by all parties that the decoder box should at least contain
some standardized de-scrambler, because nobody wants the consumer to be forced
to buy multiple boxes. It appeared however that, due to export regulations,
issues related to intellectual property rights and a general lack of suitable
candidates, it was not so easy to find this standard. In the end, the group
nominated a small subgroup of cryptologic experts that came up with a solution
after four months. Various scenarios for the de-scramblers and the conditional
access systems were then analyzed and the result was two proposals that were
put to the Steering Board of the DVB (more or less comparable with
the Board of Directors of a company).
The main problem for those who oppose this proposal is of course its necessity
to sign an agreement. Therefore it was decided to draft a standard agreement
to ensure that business takes place under fair and reasonable terms. This
standard agreement is now known as the Code of Conduct and still has
to be finalized.
The second proposal is called Multicrypt but is better known as the Common Interface. The Common Interface today consists of a detailed draft specification of a standard interface between the decoder box and a detachable module. Since the interface would have to fit all incompatible CA systems in use today, the interface was chosen at the MPEG-2 Transport Layer. This means that scrambled MPEG-2 data goes across the interface into the module and de-scrambled (thus clear) data is returned, both at a rate of up to 50 Mbit/sec. The box itself is completely standardised and does not contain the de-scrambler chip any more; this chip is now inside the detachable module. Since there are no suitable alternatives, the detachable module was chosen to be a PCMCIA card, currently in use for computer applications. For the Pay TV application, this card may contain more than the de-scrambler chip and the CA system, for instance software for an electronic programme guide. The cost of the card and that of its impact on the decoder box software is not yet clear.
The Common Interface is backed by the newcomers, who see this as a
fundamentally good and secure solution to the standardisation problem; it
allows them to cooperate and still use their own proprietary CA system.
Since it appeared to be impossible to come to a compromise, the Steering Board in the fall of 1994 accepted a package that Consisted of several elements, among which recommendations for anti-piracy legislation, transcoding issues and both the mentioned proposals: Simulcrypt and the Code of Conduct as well as the Common Interface, but neither of them mandatory. This means that a broadcaster who wishes to be DVB compliant still has both options; he can either use a proprietary system (with the standardized scrambler) and let any newcomer enter his market under the rules laid down in the Code of Conduct, or he can use the Common Interface.
Now that neither of the two options are mandatory, it is expected that both solutions will emerge and co-exist in the near future. The CA package proposed by the Steering Board still has to be accepted by the E.C. Council and it is expected that those in favour of the Common Interface will try to push the proposal to become mandatory. A disadvantage for them is that the proposal still has to be finalised and there appears to be some work left. Especially the choice of the detachable module (PCMCIA) is not clear and several parties argue about its price.
If the Common Interface is finalised soon and if it indeed becomes a mandatory standard, then it is expected that the established broadcasters, who are in favour of the Simulcrypt proposal, will put their orders for new digital systems on hold for quite a while.
