Mark Mielke wrote:
> Bruce Momjian wrote:
> > Good point. I have added the last two sentences to the documentation
> > paragraph to highlight this issue:
> >
> > <productname>OpenSSL</productname> supports a wide range of ciphers
> > and authentication algorithms, of varying strength. While a list of
> > 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.
> >
> A fact that the above misses, is that symmetric key encryption is
> actually quite cheap. It is asymmetric key encryption that is expensive.
> If you look up information on SSL accelerators, you will find claims
> that the initial SSL authentication negotiation is 1000X as expensive as
> the actual data encryption for a running session, and that SSL web
> services are usually limited by their ability to negotiate NEW sessions.
> In other words, as well intentioned and accurate as the claim you make
> above, it may be irrelevant in many real world scenarios. If you are
> going to go through all the expensive processing of having
> authentication enabled, you may as well have encryption enabled too.
OK, updated paragraph:
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
ciphersare not recommended.
-- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB
http://postgres.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
