Cryptography Reference
In-Depth Information
Satelite
Broadcast
provider
Consumer
Television
Content access device
Broadcast source
Broadcast receiver
Uplink
Figure 12.9. Digital video broadcast network
that allow consumers to access all broadcast content for a specific period of
time, package subscription services that allow consumers to access 'bundles' of
predefined broadcast content, and pay-per-view services that allow the purchase
of specific broadcast content (for example, a live broadcast of a sports event). The
compression of digital video broadcasts also allows more content to be broadcast
than that of analogue over a similar bandwidth. It thus creates the opportunity
for a much more diverse provision environment.
Figure 12.9 shows a simple example of a possible infrastructure for a digital
video broadcast network. The broadcast source transmits the broadcast content,
and is under the control of the broadcast provider . The broadcast content is
transmitted to the consumer of the content, who requires access to a suitable
broadcast receiver in order to receive the signal. In the example in Figure 12.9,
the communication channel is over the air via a satellite link, hence the broadcast
receiver takes the form of a satellite dish. However, a digital video broadcast
could just as well be transmitted by other media, such as a fibre optic cable, in
which case the broadcast receiver is any hardware device capable of receiving the
content. As well as receiving the data transmitted by the broadcast source, the
consumer requires a content access device , which has the capability of decrypting
to recover the broadcast content. While this can be implemented in software,
most content access devices are hardware devices that contain a smart card. The
critical data that is required to control access to the broadcast content, such as
cryptographic keys, will normally be stored on the smart card, thus allowing the
potential for a content access device to be used to obtain content from different
 
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