Change 'cryptmethod' from a number to a string option.  Make it global-local.
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index b56fb67..2d1a893 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -11189,7 +11189,7 @@
 ex_X(eap)
     exarg_T	*eap UNUSED;
 {
-    if (curbuf->b_p_cm == 0 || blowfish_self_test() == OK)
+    if (get_crypt_method(curbuf) == 0 || blowfish_self_test() == OK)
 	(void)get_crypt_key(TRUE, TRUE);
 }
 #endif