Gateway Datasource with SPN credentials

Indeed, documentation is not clear : "The encryption algorithm. For a cloud data source, specify None. For an on-premises data source, specify RSA-OAEP and use the gateway public key to encrypt the credentials."

I think "on-premise" means "when you use data gateway". That's why I need to encrypt.

It finally works with this script :

$keyCreds = [Microsoft.PowerBI.Api.Models.Credentials.KeyCredentials]::new($patDatabricks)
$gatewayKeyObj = [Microsoft.PowerBI.Api.Models.GatewayPublicKey]::new($gateway.publicKey.exponent, $gateway.publicKey.modulus)
$credEncrypt = [Microsoft.PowerBI.Api.Extensions.AsymmetricKeyEncryptor]::new($gatewayKeyObj)

$credentialDetails = [Microsoft.PowerBI.Api.Models.CredentialDetails]::new(
       $keyCreds, 
       [Microsoft.PowerBI.Api.Models.PrivacyLevel]::Organizational, 
       [Microsoft.PowerBI.Api.Models.EncryptedConnection]::Encrypted, 
       $credEncrypt)
$credentials = $credentialDetails.Credentials

$body = @{
    credentialDetails = @{
        credentialType      = "Key";
        credentials         = $encryptedCredentials;
        encryptedConnection = "Encrypted";
        encryptionAlgorithm = "RSA-OAEP";
        privacyLevel        = "Organizational";
    }
} | ConvertTo-Json

Invoke-PowerBIRestMethod -Url "gateways/$($gateway.id)/datasources/$($datasourceId)" -Method PATCH -Body $body