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<h1 class="settitle" align="center">NTP Symmetric Key</h1>





<span id="Top"></span><div class="header">
<p>
Next: <a href="#ntp_002ekeys-Description" accesskey="n" rel="next">ntp.keys Description</a>, Previous: <a href="dir.html#Top" accesskey="p" rel="prev">(dir)</a>, Up: <a href="dir.html#Top" accesskey="u" rel="up">(dir)</a> &nbsp; </p>
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<span id="NTP_0027s-Symmetric-Key-File-User-Manual"></span><h1 class="top">NTP&rsquo;s Symmetric Key File User Manual</h1>

<p>This document describes the symmetric key file for the NTP Project&rsquo;s
<code>ntpd</code> program.
</p>
<p>This document applies to version 4.2.8p18 of <code>ntp.keys</code>.
</p>
<span id="SEC_Overview"></span>
<h2 class="shortcontents-heading">Short Table of Contents</h2>

<div class="shortcontents">
<ul class="no-bullet">
<li><a id="stoc-Description" href="#toc-Description">1 Description</a></li>
</ul>
</div>


<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#ntp_002ekeys-Description" accesskey="1">ntp.keys Description</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#ntp_002ekeys-Notes" accesskey="2">ntp.keys Notes</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<span id="ntp_002ekeys-Description"></span><div class="header">
<p>
Previous: <a href="#Top" accesskey="p" rel="prev">Top</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; </p>
</div>
<span id="Description"></span><h2 class="chapter">1 Description</h2>

<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>.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#ntp_002ekeys-Notes" accesskey="1">Notes about ntp.keys</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<span id="ntp_002ekeys-Notes"></span><div class="header">
<p>
Previous: <a href="#ntp_002ekeys-See-Also" accesskey="p" rel="prev">ntp.keys See Also</a>, Up: <a href="#ntp_002ekeys-Description" accesskey="u" rel="up">ntp.keys Description</a> &nbsp; </p>
</div>
<span id="Notes-about-ntp_002ekeys"></span><h3 class="section">1.1 Notes about ntp.keys</h3>
<span id="index-ntp_002ekeys"></span>
<span id="index-NTP-symmetric-key-file-format"></span>



<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
&quot;Authentication Support&quot;
section of the
<code>ntp.conf(5)</code>
page.
</p>
<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 65535
may be arbitrarily set in the keys file.
</p>
<p>The key file uses the same comment conventions
as the configuration file.
Key entries use a fixed format of the form
</p>
<div class="example">
<pre class="example"><kbd>keyno</kbd> <kbd>type</kbd> <kbd>key</kbd> <kbd>opt_IP_list</kbd>
</pre></div>

<p>where
<kbd>keyno</kbd>
is a positive integer (between 1 and 65535),
<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>
<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>
<p>What follows are some key types, and corresponding formats:
</p>
<dl compact="compact">
<dt><code>MD5</code></dt>
<dd><p>The key is 1 to 16 printable characters terminated by
an EOL,
whitespace,
or
a
<code>#</code>
(which is the &quot;start of comment&quot; character).
</p>
</dd>
<dt><code>SHA</code></dt>
<dt><code>SHA1</code></dt>
<dt><code>RMD160</code></dt>
<dd><p>The key is a hex-encoded ASCII string of 40 characters,
which is truncated as necessary.
</p></dd>
</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>
<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&gt;.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#ntp_002ekeys-Files" accesskey="1">ntp.keys Files</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Files
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#ntp_002ekeys-See-Also" accesskey="2">ntp.keys See Also</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">See Also
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#ntp_002ekeys-Notes" accesskey="3">ntp.keys Notes</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Notes
</td></tr>
</table>

<hr>
<span id="ntp_002ekeys-Files"></span><div class="header">
<p>
Next: <a href="#ntp_002ekeys-See-Also" accesskey="n" rel="next">ntp.keys See Also</a>, Up: <a href="#ntp_002ekeys-Notes" accesskey="u" rel="up">ntp.keys Notes</a> &nbsp; </p>
</div>
<span id="ntp_002ekeys-Files-1"></span><h4 class="subsection">1.1.1 ntp.keys Files</h4>
<dl compact="compact">
<dt><samp>/etc/ntp.keys</samp></dt>
<dd><p>the default name of the configuration file
</p></dd>
</dl>
<hr>
<span id="ntp_002ekeys-See-Also"></span><div class="header">
<p>
Previous: <a href="#ntp_002ekeys-Files" accesskey="p" rel="prev">ntp.keys Files</a>, Up: <a href="#ntp_002ekeys-Notes" accesskey="u" rel="up">ntp.keys Notes</a> &nbsp; </p>
</div>
<span id="ntp_002ekeys-See-Also-1"></span><h4 class="subsection">1.1.2 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>
</p><hr>
<div class="header">
<p>
 &nbsp; </p>
</div>
<span id="ntp_002ekeys-Notes-1"></span><h4 class="subsection">1.1.3 ntp.keys Notes</h4>
<p>This document was derived from FreeBSD.
</p><hr>



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