shorten and fix casing of title
diff --git a/Doc/library/hashlib.rst b/Doc/library/hashlib.rst
index e33ef50..9c6c4b9 100644
--- a/Doc/library/hashlib.rst
+++ b/Doc/library/hashlib.rst
@@ -153,8 +153,8 @@
compute the digests of strings that share a common initial substring.
-Key Derivation Function
------------------------
+Key derivation
+--------------
Key derivation and key stretching algorithms are designed for secure password
hashing. Naive algorithms such as ``sha1(password)`` are not resistant against