diff --git a/services/commtest/src/tunnelbroker/tunnelbroker_utils.rs b/services/commtest/src/tunnelbroker/tunnelbroker_utils.rs
--- a/services/commtest/src/tunnelbroker/tunnelbroker_utils.rs
+++ b/services/commtest/src/tunnelbroker/tunnelbroker_utils.rs
@@ -1,9 +1,11 @@
+use anyhow::bail;
 use std::env;
 use tonic::transport::Channel;
 use tonic::transport::Error;
 pub mod proto {
   tonic::include_proto!("tunnelbroker");
 }
+use super::new_session::get_string_to_sign;
 pub use proto::tunnelbroker_service_client::TunnelbrokerServiceClient;
 
 pub async fn tonic_client_builder(
@@ -14,3 +16,14 @@
     .unwrap_or(String::from("localhost"));
   TunnelbrokerServiceClient::connect(format!("http://{}:{}", host, port)).await
 }
+
+pub async fn session_signature_device_id_format_validation(
+  client: &mut TunnelbrokerServiceClient<tonic::transport::Channel>,
+) -> anyhow::Result<()> {
+  let wrong_device_id =
+    "some:OOOQ7b2ueEmQ4QsevRWlXxFCNt055y20T1PHdoYAQRt0S6TLzZWNM6XSvdWqxm";
+  if let Ok(_) = get_string_to_sign(client, wrong_device_id).await {
+    bail!("Got success result on wrong deviceID format")
+  }
+  Ok(())
+}