Signature shadowing

book/source/09-verification.md

@@ -74,7 +74,7 @@ On the other hand, in order to verify a data signature over a text document, an
 ```{include} mermaid/09-sigtree.md
 ```
 
-### Attribute Shadowing
+### Attribute shadowing
 
 When determining preferences of a key, different signatures can be inspected.
 For example, when using a signing subkey to generate a data signature, the implementation might want to check for hash algorithm preferences on the subkey binding signature.
@@ -85,6 +85,14 @@ This is called attribute shadowing, since direct-key signature subpackets apply
 
 Note: Attribute shadowing should only be used for algorithm preferences, since there are subpacket types where shadowing makes no sense (e.g. key expiration time subpackets).
 
+### Signature shadowing
+
+When inspecting signatures on a component of an OpenPGP certificate, only the newest, effective signature for each function is considered.
+In other words; If there are three binding signatures `A, B, C` for a subkey, where `A` was created at `t0`, `B` at `t1` and `C` at `t3` with `t0 < t1 < t2 < t3`, at `t2` an implementation only needs to consider `B`, as `C` is not yet effective.
+`A` is therefore shadowed.
+
+Note: Signature shadowing is not to be mistaken with attribute shadowing.
+
 ### Revocations
 
 A signature might be *disqualified* by the presence of a revocation signature.