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<h1 class="settitle">NTP Symmetric Key</h1>
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<h2 class="unnumbered">NTP's Symmetric Key File User Manual</h2>

<p>This document describes the symmetric key file for the NTP Project's
<code>ntpd</code> program.

  <p>This document applies to version 4.2.8p11 of <code>ntp.keys</code>.

  <div class="shortcontents">
<h2>Short Contents</h2>
<ul>
<a href="#Top">NTP's Symmetric Key File User Manual</a>
</ul>
</div>

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<li><a accesskey="1" href="#ntp_002ekeys-Description">ntp.keys Description</a>
<li><a accesskey="2" href="#ntp_002ekeys-Notes">ntp.keys Notes</a>
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<h3 class="section">Description</h3>

<p>The name and location of the symmetric key file for <code>ntpd</code> can
be specified in a configuration file, by default <code>/etc/ntp.keys</code>.

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<a name="ntp_002ekeys-Notes"></a>
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<h3 class="section">Notes about ntp.keys</h3>

<p><a name="index-ntp_002ekeys-1"></a><a name="index-NTP-symmetric-key-file-format-2"></a>

  <p>This document describes the format of an NTP symmetric key file.
For a description of the use of this type of file, see the
"Authentication Support"
section of the
<code>ntp.conf(5)</code>
page.

  <p><code>ntpd(8)</code>
reads its keys from a file specified using the
<code>-k</code>
command line option or the
<code>keys</code>
statement in the configuration file.
While key number 0 is fixed by the NTP standard
(as 56 zero bits)
and may not be changed,
one or more keys numbered between 1 and 65534
may be arbitrarily set in the keys file.

  <p>The key file uses the same comment conventions
as the configuration file.
Key entries use a fixed format of the form

<pre class="example">     <kbd>keyno</kbd> <kbd>type</kbd> <kbd>key</kbd> <kbd>opt_IP_list</kbd>
</pre>
  <p>where
<kbd>keyno</kbd>
is a positive integer (between 1 and 65534),
<kbd>type</kbd>
is the message digest algorithm,
<kbd>key</kbd>
is the key itself, and
<kbd>opt_IP_list</kbd>
is an optional comma-separated list of IPs
where the
<kbd>keyno</kbd>
should be trusted.
that are allowed to serve time.
Each IP in
<kbd>opt_IP_list</kbd>
may contain an optional
<code>/subnetbits</code>
specification which identifies the number of bits for
the desired subnet of trust.
If
<kbd>opt_IP_list</kbd>
is empty,
any properly-authenticated message will be
accepted.

  <p>The
<kbd>key</kbd>
may be given in a format
controlled by the
<kbd>type</kbd>
field.
The
<kbd>type</kbd>
<code>MD5</code>
is always supported.
If
<code>ntpd</code>
was built with the OpenSSL library
then any digest library supported by that library may be specified.
However, if compliance with FIPS 140-2 is required the
<kbd>type</kbd>
must be either
<code>SHA</code>
or
<code>SHA1</code>.

  <p>What follows are some key types, and corresponding formats:

     <dl>
<dt><code>MD5</code><dd>The key is 1 to 16 printable characters terminated by
an EOL,
whitespace,
or
a
<code>#</code>
(which is the "start of comment" character).

     <br><dt><code>SHA</code><br><dt><code>SHA1</code><br><dt><code>RMD160</code><dd>The key is a hex-encoded ASCII string of 40 characters,
which is truncated as necessary.
</dl>

  <p>Note that the keys used by the
<code>ntpq(8)</code>
and
<code>ntpdc(8)</code>
programs are checked against passwords
requested by the programs and entered by hand,
so it is generally appropriate to specify these keys in ASCII format.

  <p>This section was generated by <strong>AutoGen</strong>,
using the <code>agtexi-cmd</code> template and the option descriptions for the <code>ntp.keys</code> program.
This software is released under the NTP license, &lt;http://ntp.org/license>;.

<ul class="menu">
<li><a accesskey="1" href="#ntp_002ekeys-Files">ntp.keys Files</a>:                   Files
<li><a accesskey="2" href="#ntp_002ekeys-See-Also">ntp.keys See Also</a>:                See Also
<li><a accesskey="3" href="#ntp_002ekeys-Notes">ntp.keys Notes</a>:                   Notes
</ul>

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<h4 class="subsection">ntp.keys Files</h4>

     <dl>
<dt><span class="file">/etc/ntp.keys</span><dd>the default name of the configuration file
</dl>
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<h4 class="subsection">ntp.keys See Also</h4>

<p><code>ntp.conf(5)</code>,
<code>ntpd(1ntpdmdoc)</code>,
<code>ntpdate(1ntpdatemdoc)</code>,
<code>ntpdc(1ntpdcmdoc)</code>,
<code>sntp(1sntpmdoc)</code>
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<h4 class="subsection">ntp.keys Notes</h4>

<p>This document was derived from FreeBSD.

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