Document that null ciphers are not recommended.

Mark Mielke

diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 7b6d920d8c0e8019a92c5c19f81cc88506648e6b..892449005747f4a3108656338a2765ae1a1a9507 100644 (file)
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -1604,12 +1604,20 @@ $ <userinput>kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`</userinput
    ciphers can be specified in the <productname>OpenSSL</productname>
    configuration file, you can specify ciphers specifically for use by
    the database server by modifying <xref linkend="guc-ssl-ciphers"> in
-   <filename>postgresql        .conf</>.  It is possible to have authentication
-   without the overhead of encryption by using <literal>NULL-SHA</> or
-   <literal>NULL-MD5</> ciphers.  However, a man-in-the-middle could read
-   and pass communications between client and server.
+   <filename>postgresql        .conf</>.
   </para>
 
+  <note>
+   <para>
+    It is possible to have authentication without encryption overhead by
+    using <literal>NULL-SHA</> or <literal>NULL-MD5</> ciphers.  However,
+    a man-in-the-middle could read and pass communications between client
+    and server.  Also, encryption overhead is minimal compared to the
+    overhead of authentication.  For these reasons NULL ciphers are not
+    recommended.
+   </para>
+  </note>
+
   <para>
    To start in <acronym>SSL</> mode, the files <filename>server.crt</>
    and <filename>server.key</> must exist in the server's data directory.