diff --git a/services/tunnelbroker/src/cxx_bridge.rs b/services/tunnelbroker/src/cxx_bridge.rs
--- a/services/tunnelbroker/src/cxx_bridge.rs
+++ b/services/tunnelbroker/src/cxx_bridge.rs
@@ -55,6 +55,7 @@
     pub fn getConfigParameter(parameter: &str) -> Result<String>;
     pub fn isSandbox() -> Result<bool>;
     pub fn sessionSignatureHandler(deviceID: &str) -> SessionSignatureResult;
+    pub fn getStringToSign(deviceID: &str) -> Result<String>;
     pub fn newSessionHandler(
       deviceID: &str,
       publicKey: &str,
diff --git a/services/tunnelbroker/src/libcpp/Tunnelbroker.h b/services/tunnelbroker/src/libcpp/Tunnelbroker.h
--- a/services/tunnelbroker/src/libcpp/Tunnelbroker.h
+++ b/services/tunnelbroker/src/libcpp/Tunnelbroker.h
@@ -7,6 +7,7 @@
 rust::String getConfigParameter(rust::Str parameter);
 bool isSandbox();
 SessionSignatureResult sessionSignatureHandler(rust::Str deviceID);
+rust::String getStringToSign(rust::Str deviceID);
 NewSessionResult newSessionHandler(
     rust::Str deviceID,
     rust::Str publicKey,
diff --git a/services/tunnelbroker/src/libcpp/Tunnelbroker.cpp b/services/tunnelbroker/src/libcpp/Tunnelbroker.cpp
--- a/services/tunnelbroker/src/libcpp/Tunnelbroker.cpp
+++ b/services/tunnelbroker/src/libcpp/Tunnelbroker.cpp
@@ -72,6 +72,11 @@
       .toSign = toSign, .grpcStatus = {.statusCode = GRPCStatusCodes::Ok}};
 }
 
+rust::String getStringToSign(rust::Str deviceID) {
+  comm::network::database::DatabaseManager::getInstance().findSessionSignItem(
+      std::string{deviceID});
+}
+
 NewSessionResult newSessionHandler(
     rust::Str deviceID,
     rust::Str publicKey,