How to create GCP Dataflow

Good Evening everyone,
I am trying to creating a GCP dataflow with customer-managed keys. But I am not able to figure out the name for the customer-managed key name. Following is my code
for example:
resource “google_dataflow_job” “dataflow_job” {

project = var.project_id
region = var.region_name
name = var.data_flow_name
#data_flow_key_name = var.data_flow_encryption_key
on_delete = “cancel”
template_gcs_path = “gs://dataflow-templates-us-central1/latest/Cloud_PubSub_to_GCS_Text”
temp_gcs_location = “gs://test/tmp”
service_account_email = var.service_account_email
#ip_configuration = “WORKER_IP_PRIVATE”
parameters = {
“inputTopic”: “projects/{var.project_id}/topics/{var.topic_name}”,
“outputDirectory”: “gs://{var.storage_bucket_name}/", "ouputFilenamePrefix": "{var.log_sink_name}”,