FIRMWARE DESCRIPTION
System Security
2.10
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19.01.2007
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3.2.2 EasySubs
EasySubs is a powerful technique for handling of subscription information in the FT.
Conventional FT implementations include a table of all subscribed PTs with their UAKs.
Since memory is limited, the FT may only support a very limited number of subscriptions.
The EasySubs technique avoids storage of UAKs in the FT but provides an efficient means
for on-demand computation of UAKs from other information already available. Due to
EasySubs, FTs of Höft & Wessel support an unlimited number of PT subscriptions.
EasySubs if fully compliant with the DECT standard. It is used for both, on-air and offline
subscriptions. EasySubs is interoperable with GAP-compliant PTs of other manufacturers.
The security of the DECT system is fully preserved by EasySubs by introducing an additional
key, the
SMK
(subscription master key). The SMK is stored in the FT in non-volatile memory.
It is used during on-demand computation of UAKs.
Only a single SMK is needed, independent of the number of PTs to be subscribed.
The default SMK (factory setting) is: 00000000
The PT stores subscription information in the conventional way, i.e. EasySubs only affects
the FT.
In multi-cell networks all RFPs must be programmed with the same values of PIN and SMK
respectively.
A big advantage of EasySubs: Any PT must only be subscribed to a single RFP of a multi-
cell network. Then it automatically communicates with all other RFPs of that network.
Note: If the system operator modifies the values of PIN and/or SMK at his FT, all previous
PT subscriptions get invalid and must be renewed.