1 Type of Question
Task-oriented Question that should eventually result in a Recommendation.
2 Motivation
Studies are currently under way in several countries, on ways
to improve the security of conditional access systems used for
subscription, pay-per-view and similar services distributed to
the home by cable television. The need for such studies
immediately emerges when the security and viability of
conditional access systems currently used in Europe, the United
States and elsewhere is assessed.
Such an assessment shows the evident need to develop new,
more performing, pirate-proof systems that would enable a cable
television system to implement programme distribution to the
home (be it a subscription or a pay-per-view service) with a
security level adequate to make it commercially viable. Indeed,
conditional access systems that were considered to be totally
secure when they were developed only a few years ago for
television distribution to the home, have been invariably
"compromised" by pirates, who extract the conditional
access enabling information and sell it at a fraction of the
regular subscription fee.
Any conditional access system can be expected to eventually
be compromised, irrespective of its sophistication, if the
compromised enabling information can be sold to a sufficiently
large base of customers.
It seems that a conditional access system will be more secure
if the conditions below are met:
- the scrambling process is highly secure;
- the cryptographic algorithm is highly secure;
- the key and the entitlement information are changed
at frequent intervals;
- subscribers are divided into small sub-entities, each
with its own key and entitlement.
The concurrence of these conditions makes it expensive to
compromise the system, and it reduces the pirate's customer
base, to the point where piracy is no longer financially viable.
Another very important aspect that is related to conditional
access is the provision of measures to prevent a distributed
programme from being copied, unless the owner of its
intellectual property rights authorizes such copying. Two
approaches, which are not mutually exclusive, are being
investigated to achieve this goal:
- The conditional access system could be designed in
such a way as to separate viewing authorization from copying
authorization. In other words it would provide a viewable
output to those users that are authorized to view the
programme, but it would provide a recordable output only to
those users that are separately authorized to copy it. The
issue is further complicated by the need of intellectual
property holders to have various degrees of authorization,
namely: no copy, one copy or any number of copies.
- The programme could be "watermarked" with a
hidden coded information, which can neither be removed nor
altered, and would identify the holder to the programme
intellectual property rights, thus allowing to trace the
history of unauthorized copies and take appropriate legal
action against pirates.
The study should thus focus on the following lines:
- the specification of a highly secure scrambling
system;
- the specification of a highly secure cryptographic
system that can be implemented at a viable cost for cable
television distribution to the home, namely, in a
mass-produced consumer equipment environment;
- the specification of a key and an enabling
information distribution system that has adequate capacity
and flexibility to serve the diversified requirements of
various cable television systems and their various
subscribers;
- the development of a set of guidelines on the optimal
time interval at which the key and the enabling information
should be updated, and on the optimal size of the subscriber
population to which the same enabling information is
assigned;
- the specifications for an application of the
cryptographic system appropriate to implement copy
protection at various levels of authorization (no copy, one
copy only, any number of copies);
- the specifications for a highly secure watermarking
system that would not affect the quality of the distributed
programme.
3 Questions
- What scrambling approaches can be recommended for
digital cable television distribution to the home?
- What is the capacity required of a conditional access
system for cable television distribution to the home, in
terms of number of individually addressable subscribers or
subscriber groups, etc.?
- What are the specifications for a (preferably unique)
cryptographic approach appropriate to such conditional
access system?
- What are the specifications for an application of the
cryptographic system, appropriate to implement copy
protection at various levels of authorization (no copy, one
copy only, any number of copies)?
- What are the specifications for the (preferably
unique) removable (e.g. ISO-7816, PCMCIA, etc.)
cryptographic device (e.g. smart card), if one is used
in such a conditional access system?
- How often should the conditional access key be
updated?
- Which criteria should be used to time the replacement
of the (removable) cryptographic device or of the enabling
information in it?
- What is the optimal size of the subscriber population
to which the same key and enabling information may be safely
assigned?
- Can conditional access solutions developed for
terrestrial and satellite broadcasting be used for cable
television also?
- What are the specifications for a highly secure
watermarking system that would not affect the quality of the
distributed programme?
4 Expected results and anticipated target dates
Depending on the contributions that will be received, and on
progress in the preparatory activity of the Rapporteur, the
studies will likely result in the preparation of draft new
Recommendations by 2003, providing specifications and
recommended operating practices.
5 Relationships
Exchange of information with ITU-R Study Group 6 would be
useful, to take into account possible parallel studies of Study
Group 6. However, it is not clear at this moment whether it
would be desirable, or indeed possible to develop a conditional
access system, capable simultaneously and optimally to meet the
different requirements of cable television and of broadcast
television.
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