Siemens Simatic RTU303xC Series Operating Instructions Manual page 225

● Key length
Specifies the length of the pre-shared key in bytes.
The following lengths are pre-selected depending on the configured key wrap algorithm.
– For AES-128: 16
– For AES-256: 32
● Max. number of key exchange requests
If the configured number of statistics queries of the master is exceeded within the key
exchange interval, the RTU enters a message in the diagnostics buffer.
Range of values: 2...255 Default setting: 5
● Authentication requests before key exchange
Maximum number of authentication requests of the RTU with the master. When this
number is reached, the session key is renewed.
Range of values: 1...10000 Default setting: 1000
Recommendation: Set the number for the RTU twice as high as for the master.
● Key exchange interval (min)
Period after which the key is exchanged again between the RTU and the master. The
interval must be matched up on both communications partners.
Range of values: 0...65535 min. at 0 (zero), the key is never changed (function disabled).
Default setting: 15 min.
Recommendation: Set the key exchange interval for the RTU twice as high as for the
master.
● Key exchange monitoring time
Maximum waiting time for the response from the master to an authentication request of
the RTU.
Exceeding the waiting time is evaluated as an error by the RTU. In this case, the RTU
generates a security event and sends this to the master.
Range of values: 1... 65535 s Default setting: 5
● Import key file
The pre-shared key can either be imported as a file or configured manually.
The output box displays the name of the last imported key file.
Import the pre-shared key from the file system of the configuration PC if the key was
generated by the master or another system.
Import the key into the RTU with the "Import" button.
● Pre-shared key
Here you can configure the pre-shared key manually. Enter the pre-shared key as
hexadecimal values.
The pre-shared key of the RTU must be identical to the pre-shared key of the master.
RTU303xC
Operating Instructions, 06/2019, C79000-G8976-C382-06
Configuration (WBM)
4.23 Telecontrol
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