diff --git a/src/groups.md b/src/groups.md
index 9900fb9..a4b2b6f 100644
--- a/src/groups.md
+++ b/src/groups.md
@@ -57,4 +57,6 @@ chain (which if they were attempting to censor other messages would
  reveal such censorship)
  
 Finally: We are actively working on adding non-repudiation to Cwtch servers such
-that they themselves are restricted in what they can censor efficiently.
\ No newline at end of file
+that they themselves are restricted in what they can censor efficiently.
+
+<!-- I might have missed it but I think this is the first mention of each message being signed by the sender (and that the message contains unique identifiers)? Might be great to have a 'message_format.md' where message structure/constructure is explained/introduced earlier? I also can't tell how the session key is applied to the message at this point.  -->
\ No newline at end of file