Change 'cryptmethod' from a number to a string option. Make it global-local.
diff --git a/runtime/doc/editing.txt b/runtime/doc/editing.txt
index ba4da02..4d5b00f 100644
--- a/runtime/doc/editing.txt
+++ b/runtime/doc/editing.txt
@@ -1371,10 +1371,17 @@
To disable the encryption, reset the 'key' option to an empty value: >
:set key=
-You can use the 'cryptmethod' option to select the type of encryption. Do
-this before writing the file. When reading an encrypted file it will be set
-automatically to the method used when that file was written. You can change
-'cryptmethod' before writing that file to change the method.
+You can use the 'cryptmethod' option to select the type of encryption, use one
+of these two: >
+ :setlocal cm=zip " weak method, backwards compatible
+ :setlocal cm=blowfish " strong method
+Do this before writing the file. When reading an encrypted file it will be
+set automatically to the method used when that file was written. You can
+change 'cryptmethod' before writing that file to change the method.
+To set the default method, used for new files, use one of these in your
+|vimrc| file: >
+ set cm=zip
+ set cm=blowfish
When writing an undo file, the same key and method will be used for the text
in the undo file. |persistent-undo|.