--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -2056,12 +2056,21 @@ A jump table for the options with a shor
 	Method used for encryption when the buffer is written to a file:
 							*pkzip*
 		0	PkZip compatible method.  A weak kind of encryption.
-			backwards compatible with Vim 7.2 and older.
+			Backwards compatible with Vim 7.2 and older.
 							*blowfish*
-		1	Blowfish method.  Strong encryption.  Not compatible
-			with Vim 7.2 and older.
+		1	Blowfish method.  Strong encryption.  Requires Vim 7.3
+			or later, files can NOT be read by Vim 7.2 and older.
+			This adds a "seed" to the file, every time you write
+			the file the encrypted bytes will be different.
+
 	When reading an encrypted file 'cryptmethod' will be set automatically
-	to detected method for the file being read.
+	to the detected method of the file being read.  Thus if you write it
+	without changing 'cryptmethod' the same method will be used.
+	Changing 'cryptmethod' does not mark the file as modified, you have to
+	explicitly write it when not making modifications.
+	Also see |:X|.
+	When a new encryption method is added in a later version of Vim, and
+	the current version does not recognize it, you will get	*E821* .
 
 
 						*'cscopepathcomp'* *'cspc'*