User's Manual

Doc. No.
Rev.
Date
1.00
2011-12-08
Damm Cellular Systems A/S, Denmark
TETRAFLEX
®
V7.5 MANUAL - Authentication and Encryption
TetraFlex® 7.5 Manual 3-54
3.4 AUTHENTICATION AND ENCRYPTION
3.4.1 Description
This section describes in detail the function of the Security Key Set used for authentication
and encryption.
Only the method is described, for further information regarding the Subscriber Register, BSC,
distribution of subscriber data etc. please consult the relevant manual sections.
3.4.2 Definitions
K
The key value file generated by the terminal programmer. File is in plain
text and contains key value associated to TEI
Dongle Key
The secret key programmed in the Node Dongle. The Dongle Key is
enabling the key register in the subscriber register
K
1
The Security Keys derived from the K file and placed in the key register
Security set
The distributed key sets. Should be updated at regular intervals
3.4.3 Description
The key file produced by the terminal programmer (K) is read in to the system and is
encrypted using the Dongle Key and placed in a key register (K
1
).
This key register is now “protected” by the dongle key.
This means that if the key register is moved to another node, the Dongle key must be moved
as well.
The content of the key register (K
1
), decrypted with the dongle Key, and the TEI or SIM
reference value is used to produce a security set (Derived keys) which is placed in the Master
Subscriber Register and distributed to the Subscriber Register on the other nodes as SSI +
Security Set. After this the TEI / SIM reference is essentially no longer used.
When updating the Security Set, the K
1
key and the SSI is used to generate a new distributed
Security Set.