The Home Network Public Key Identifier determines which public key was used to generate the SUCI sent to the AMF. See TS 23.003 Section 2.2B Section 5.
The URL of Azure Key Vault secret containing the private key, versioned or unversioned. For example: https://contosovault.vault.azure.net/secrets/mySuciPrivateKey/562a4bb76b524a1493a6afe8e536ee78.