Siemens CP 1243-1 Operating Instructions Manual page 66

Configuration
4.9 Security
● SHA-1 interlock
Setting to select whether the CP may use the secure hash algorithm SHA-1 if "SHA-256"
was configured as the Secure hash algorithm and the master does not support SHA-256.
Range of values:
– SHA-1 mode not allowed
– SHA-1 mode allowed
Default setting: SHA-1 mode not allowed
● Secure hash algorithm (SHA)
Selection of the Secure Hash Algorithm (SHA)
Range of values:
– SHA-1
– SHA-256
Default setting: 256
● Key wrap algorithm
Selection of the Advanced Encryption Standard (AES)
Range of values:
– AES-128
– AES-256
Default setting: AES-128
● Key length
Specifies the length of the pre-shared key in bytes.
Permitted range: 16 - 128 Depending on the secure hash algorithm configured in STEP 7
above, the following lengths are preset:
– For SHA-1: 16
– For SHA-256: 32
The value 0 (zero) is not permitted.
● Max. number of statistics queries
If the configured number of statistics queries of the master is exceeded within the key
exchange interval, the CP enters a message in the diagnostics buffer of the CPU.
Range of values: 2...255 Default setting: 5
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The CP may not use SHA-1. If the master does not support SHA-256, no connection
will be established.
The CP can use SHA-1 if the master does not support SHA-256.
Operating Instructions, 04/2017, C79000-G8976-C365-03
CP 1243-1