diff --git a/book/source/04-certificates.md b/book/source/04-certificates.md
index 408ccfb..60da4d6 100644
--- a/book/source/04-certificates.md
+++ b/book/source/04-certificates.md
@@ -261,6 +261,16 @@ This section only contains notes and still needs to be written
 
 Minimized versions, merging, effective "append only" semantics, ...
 
+### "Naming" a certificate in user-facing contexts - fingerprints and beyond
+
+```{admonition} TODO
+:class: warning
+
+In v4, a 20 byte fingerprint in hex representation was used to name certificates, even in user-facing contexts.
+
+For v6, this type of approach is discouraged, but a replacement mechanism is still pending.
+```
+
 ### Merging
 
 - How to merge two copies of the same certificate?