Please check sample source code on GitHub (referenced in same article).

Key Vault Config:

https://github.com/a-patel/dotnet-data-protection-labs/blob/master/src/AspNetCoreDataProtectionLabs.AzureKeyVault/appsettings.json#L3

Blob Storage Config:

https://github.com/a-patel/dotnet-data-protection-labs/blob/master/src/AspNetCoreDataProtectionLabs.AzureBlobStorage/appsettings.json#L3