diff --git a/src/devices.ml b/src/devices.ml
index 6f7c1968..02ecad17 100644
--- a/src/devices.ml
+++ b/src/devices.ml
@@ -1,3 +1,5 @@
+(* TODO KV store *)
+
 module Secmod_signkey = struct
   type t = {
     secmod_key: Signkey.t;
diff --git a/src/signkey.ml b/src/signkey.ml
index e7923785..0bdd3b37 100644
--- a/src/signkey.ml
+++ b/src/signkey.ml
@@ -6,6 +6,7 @@ type t = {
   stamp_expire: Ptime.t;
   stamp_end: Ptime.t;
   sign: string -> EddsaSignature.t;
+  (* signature of this key by offline master key *)
   master_sig: EddsaSignature.t option;
 }