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The encryption service is addressed via the repository (here using the CE repository as an example).
CE.encryptionservice.type=aes_gcm
CE.encryptionservice.aes_gcm.secret=<please use a key for encryption>
It makes sense that the secret is stored as an alias in the keystore, which points to a password in the KeystoreService https://kgs-software.atlassian.net/wiki/spaces/DOCUEN/pages/1671659521/Encryption+Service#Einrichten-des-Keystores. If no keystore is used, the secret must be entered here in plain text.
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