diff --git a/services/commtest/src/lib.rs b/services/commtest/src/lib.rs
--- a/services/commtest/src/lib.rs
+++ b/services/commtest/src/lib.rs
@@ -2,3 +2,4 @@
 pub mod blob;
 pub mod constants;
 pub mod tools;
+pub mod tunnelbroker;
diff --git a/services/commtest/src/tunnelbroker/mod.rs b/services/commtest/src/tunnelbroker/mod.rs
new file mode 100644
--- /dev/null
+++ b/services/commtest/src/tunnelbroker/mod.rs
@@ -0,0 +1,2 @@
+pub mod new_session;
+pub mod tunnelbroker_utils;
diff --git a/services/commtest/src/tunnelbroker/new_session.rs b/services/commtest/src/tunnelbroker/new_session.rs
new file mode 100644
--- /dev/null
+++ b/services/commtest/src/tunnelbroker/new_session.rs
@@ -0,0 +1,17 @@
+use crate::tools::Error;
+use crate::tunnelbroker::tunnelbroker_utils::{
+  proto::SessionSignatureRequest, TunnelbrokerServiceClient,
+};
+use tonic::Request;
+
+pub async fn get_string_to_sign(
+  client: &mut TunnelbrokerServiceClient<tonic::transport::Channel>,
+  device_id: &str,
+) -> Result<String, Error> {
+  let response = client
+    .session_signature(Request::new(SessionSignatureRequest {
+      device_id: String::from(device_id),
+    }))
+    .await?;
+  Ok(response.into_inner().to_sign)
+}
diff --git a/services/commtest/src/tunnelbroker/tunnelbroker_utils.rs b/services/commtest/src/tunnelbroker/tunnelbroker_utils.rs
new file mode 100644
--- /dev/null
+++ b/services/commtest/src/tunnelbroker/tunnelbroker_utils.rs
@@ -0,0 +1,4 @@
+pub mod proto {
+  tonic::include_proto!("tunnelbroker");
+}
+pub use proto::tunnelbroker_service_client::TunnelbrokerServiceClient;