diff --git a/proto/umbra/common_frames.proto b/proto/umbra/common_frames.proto
new file mode 100644
index 0000000..85dd08c
--- /dev/null
+++ b/proto/umbra/common_frames.proto
@@ -0,0 +1,9 @@
+syntax = "proto3";
+
+package umbra.common_frames;
+
+message ContentFrame {
+    uint32 domain = 1;
+    uint32 tag = 2;
+    bytes bytes = 3;
+}
\ No newline at end of file