add RSA verification support
diff --git a/docs/exceptions.rst b/docs/exceptions.rst
index 0982426..7f9ae34 100644
--- a/docs/exceptions.rst
+++ b/docs/exceptions.rst
@@ -10,8 +10,8 @@
 
 .. class:: InvalidSignature
 
-    This is raised when the verify method of a hash context's computed digest
-    does not match the expected digest.
+    This is raised when signature verification fails. This can occur with
+    HMAC or asymmetric key signature validation.
 
 
 .. class:: NotYetFinalized