--- a/runtime/doc/editing.txt
+++ b/runtime/doc/editing.txt
@@ -1366,10 +1366,18 @@ this before writing the file.  When read
 automatically to the method used when that file was written.  You can change
 'cryptmethod' before writing that file to change the method.
 
-When reading a file that has been encrypted and this option is not empty, it
-will be used for decryption.  If the value is empty, you will be prompted to
-enter the key.  If you don't enter a key, the file is edited without being
-decrypted.
+						*E817* *E818* *E819*
+When encryption does not work properly, you would be able to write your text
+to a file and never be able to read it back.  Therefore a test is performed to
+check if the encryption works as expected.  If you get one of these errors
+don't write the file encrypted!  You need to rebuild the Vim binary to fix
+this.
+
+When reading a file that has been encrypted and the 'key' option is not empty,
+it will be used for decryption.  If the value is empty, you will be prompted
+to enter the key.  If you don't enter a key, or you enter the wrong key, the
+file is edited without being decrypted.  There is no warning about using the
+wrong key (this makes brute force methods to find the key more difficult).
 
 If want to start reading a file that uses a different key, set the 'key'
 option to an empty string, so that Vim will prompt for a new one.  Don't use