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<chapter id="client-authentication">
<para>
The ident authentication method works by obtaining the client's
- operating system user name and determining the allowed database
+ operating system user name, then determining the allowed database
user names using a map file that lists the permitted
corresponding pairs of names. The determination of the client's
user name is the security-critical point, and it works differently
</para>
</blockquote>
</para>
+
+ <para>
+ Some ident servers have a nonstandard option that causes the returned
+ user name to be encrypted, using a key that only the originating
+ machine's administrator knows. This option <emphasis>must not</> be
+ used when using the ident server with <productname>PostgreSQL</>,
+ since <productname>PostgreSQL</> does not have any way to decrypt the
+ returned string to determine the actual user name.
+ </para>
</sect3>
<sect3>