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Director improves on this by automatically changing the encryption key every few
seconds. To achieve this, a new key is generated (typically every 20 seconds) and
is automatically and securely transmitted to the receivers. Tight control over timing
means that the key changes happen seamlessly. The keys are securely transmitted
in encrypted form within the transport stream using Entitlement Control Messages
(ECMs) and multiple keys can be transmitted to encrypt more than one service.
Each service will be encrypted differently and will always have a unique key and
separate ECM.
3.11.4.5.2
Authorizing the Receiver
The Ericsson Director system provides full Conditional Access to precisely control
what a viewer can watch. With BISS, the encryption key is used to control the
security of the link and determine whether the viewer can watch the content. With
Director, these two functions are separated.
The security of the transmission is protected by the variable key system, making it
highly secure. Unless the receiver can utilize the continuous stream of ECMs which
provide the encrypted session word, the clear session word cannot be recovered
and so the link remains secure.
However, even if the ECM can be decrypted by a genuine Director receiver, there is
a further stage of protection to go through before the content can be viewed. This
mechanism involves the concept of "entitlements" and means that the receiver must
be specifically authorized for each program it can decode. This may sound complex,
but the Director system makes it incredibly simple. The power this provides is
equally incredible since you control what each receiver is authorized to view putting
you in complete control.
Central to this mechanism is a scheduler, accessible by the head-end operator,
which can list all of the programs being aired. The scheduler can assign an
entitlement to any program that needs to be protected. The Director system will
automatically monitor the scheduler and will securely carry the entitlements using
Entitlement Management Messages (EMMs) to the receiver. If it is a genuine
Director receiver, then it will be able to decrypt the ECM and recover the encryption
key, but it will also check the entitlement being carried in the EMM against a list of
pre-stored entitlements. If there is a match, the received session key will be used to
decrypt. If there is no match, then decryption will not take place and the user will be
informed that viewing of the content is not authorized. Since there is a separate
ECM for every service, this process will occur independently on every channel,
allowing the content to be protected individually in a multi-channel environment.
3.11.4.5.3
Addressing the Receiver
Each unit has a unique address or serial number and a unique unit type. In this case
the unit type is RX8000.
The Customization Serial Number (sometimes referred to as the "Unique
Hardware ID") is displayed on the Customization web page as shown in Figure
3.73. It is not to be confused with the unit or production serial number often stamped
on the back panel of the RX8000 chassis.
EN/LZT 790 0005 R7A
Using the Equipment
3-153
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