Motorola V186 - Cell Phone - GSM System Planner Manual page 142

When an RTU is first configured and stars up (cold start in MOSCAD and MOSCAD-L
RTUs), the key index is set to '0' (non-encrypted mode). Encryption is then activated by
changing the Active Key index to a number other than '0' (1-9). This is done using the
MDLC Encryption Tool.
The replacement of the encryption key is initiated by the MDLC Encryption tool.
Successful replacement of the active key requires that all RTUs in the system be time-
synchronized by the IP Gateway.
To compensate for possible time drifts during a transition from one encryption key to
another, there is a configurable time interval where both the old and new keys are valid.
Accept old and
new keys for
RX.
Switch to
new key
TE1 is the interval, in seconds, which represents the possible time drift.
Note: It is recommended that at least one non-encrypted IP Gateway (FIU) will be
connected to the system to enable communication with non-encrypted RTUs when
necessary
Encryption in the STS/ToolBox MDLC Driver
Once KF is defined in the MDLC Encryption Tool, it can be set as the Active File in the
STS/ToolBox MDLC driver The Active Key Index is then set to the same index (1-9) of
the Active Key of the system. This enables the STS or ToolBox to exchange data with
encrypted RTUs.
In the event that the STS/ToolBox must send a non-encrypted message, (to an RTU that
performed a cold restart), the encryption should be deactivated by setting the MDLC
driver Key Index to 0.
Uses old
key for TX.
Uses new
key for TX.
TE1
TE2
138
Communications
Uses new key for
TX. Accept new
key for RX.
time