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<h3><tt>ntp-keygen</tt> - generate public and private keys</h3>
<p><img src="pic/alice23.gif" alt="gif" align="left"><a href="http://www.eecis.udel.edu/%7emills/pictures.html">from <i>Alice's Adventures in Wonderland</i>, Lewis Carroll</a></p>
<p>Alice holds the key.</p>
<p>Last update:
<!-- #BeginDate format:En2m -->11-Jan-2018 11:55<!-- #EndDate -->
UTC</p>
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<h4>Related Links</h4>
<script type="text/javascript" language="javascript" src="scripts/manual.txt"></script>
<h4>Table of Contents</h4>
<ul>
<li class="inline"><a href="#synop">Synopsis</a></li>
<li class="inline"><a href="#descrip">Description</a></li>
<li class="inline"><a href="#run">Running the program</a></li>
<li class="inline"><a href="#cmd">Command Line Options</a></li>
<li class="inline"><a href="#rand">Random Seed File</a></li>
<li class="inline"><a href="#fmt">Cryptographic Data Files</a></li>
<li class="inline"><a href="#bug">Bugs</a></li>
</ul>
<hr>
<h4 id="synop">Synopsis</h4>
<p id="intro"><tt>ntp-keygen [ -deGHIMPT ] [ -b <i>modulus</i> ] [ -c [ RSA-MD2 | RSA-MD5 | RSA-SHA
| RSA-SHA1 | RSA-MDC2 | RSA-RIPEMD160 | DSA-SHA | DSA-SHA1 ] ]
[ -C <i>cipher</i> ] [-i <i>group</i> ] [ -l <em>days</em>]
[ -m <i>modulus</i> ] [ -p <i>passwd1</i> ] [ -q <i>passwd2</i> ]
[ -S [ RSA | DSA ] ] [ -s <i>host</i> ] [ -V <i>nkeys</i> ]</tt></p>
<h4 id="descrip">Description</h4>
<p>This program generates cryptographic data files used by the NTPv4
authentication and identity schemes. It can generate message digest keys
used in symmetric key cryptography and, if the OpenSSL software library
has been installed, it can generate host keys, sign keys, certificates,
and identity keys and parameters used by the Autokey public key
cryptography. The message digest keys file is generated in a format
compatible with NTPv3. All other files are in PEM-encoded printable ASCII
format so they can be embedded as MIME attachments in mail to other
sites.</p>
<p>When used to generate message digest keys, the program produces a file
containing ten pseudo-random printable ASCII strings suitable for the MD5
message digest algorithm included in the distribution. If the OpenSSL
library is installed, it produces an additional ten hex-encoded random bit
strings suitable for the SHA1, AES-128 CMAC, and other message digest
algorithms. The message digest keys file must be distributed and stored
using secure means beyond the scope of NTP itself. Besides the keys used
for ordinary NTP associations, additional keys can be defined as passwords
for the <tt><a href="ntpq.html">ntpq</a></tt>
and <tt><a href="ntpdc.html">ntpdc</a></tt> utility programs.</p>
<p>The remaining generated files are compatible with other OpenSSL
applications and other Public Key Infrastructure (PKI)
resources. Certificates generated by this program are compatible with
extant industry practice, although some users might find the
interpretation of X509v3 extension fields somewhat liberal. However,
the identity keys are probably not compatible with anything other than
Autokey.</p>
<p>Some files used by this program are encrypted using a private
password. The <tt>-p</tt> option specifies the password for local
encrypted files and the <tt>-q</tt> option the password for encrypted
files sent to remote sites. If no password is specified, the host name
returned by the Unix <tt>gethostname()</tt> function, normally the DNS
name of the host, is used.</p>
<p>The <tt>pw</tt> option of the <tt>crypto</tt> configuration command
specifies the read password for previously encrypted local files.
This must match the local password used by this program. If not
specified, the host name is used. Thus, if files are generated by
this program without password, they can be read back by <tt>ntpd</tt>
without password, but only on the same host.</p>
<p>Normally, encrypted files for each host are generated by that host
and used only by that host, although exceptions exist as noted later
on this page. The symmetric keys file, normally
called <tt>ntp.keys</tt>, is usually installed in <tt>/etc</tt>.
Other files and links are usually installed
in <tt>/usr/local/etc</tt>, which is normally in a shared filesystem
in NFS-mounted networks and cannot be changed by shared clients. The
location of the keys directory can be changed by the <tt>keysdir</tt>
configuration command in such cases. Normally, this is
in <tt>/etc</tt>.</p>
<p>This program directs commentary and error messages to the standard
error stream <tt>stderr</tt> and remote files to the standard output
stream <tt>stdout</tt> where they can be piped to other applications
or redirected to files. The names used for generated files and links
all begin with the string <tt>ntpkey</tt> and include the file type,
generating host and filestamp, as described in
the <a href="#fmt">Cryptographic Data Files</a> section below</p>
<h4 id="run">Running the Program</h4>
<p>To test and gain experience with Autokey concepts, log in as root and
change to the keys directory, usually <tt>/usr/local/etc</tt>. When
run for the first time, or if all files with names
beginning <tt>ntpkey</tt> have been removed, use
the <tt>ntp-keygen</tt> command without arguments to generate a
default RSA host key and matching RSA-MD5 certificate with expiration
date one year hence. If run again without options, the program uses
the existing keys and parameters and generates only a new certificate
with new expiration date one year hence.</p>
<p>Run the command on as many hosts as necessary. Designate one of them
as the trusted host (TH) using <tt>ntp-keygen</tt> with
the <tt>-T</tt> option and configure it to synchronize from reliable
Internet servers. Then configure the other hosts to synchronize to
the TH directly or indirectly. A certificate trail is created when
Autokey asks the immediately ascendant host towards the TH to sign its
certificate, which is then provided to the immediately descendant host
on request. All group hosts should have acyclic certificate trails
ending on the TH.</p>
<p>The host key is used to encrypt the cookie when required and so must
be RSA type. By default, the host key is also the sign key used to
encrypt signatures. A different sign key can be assigned using
the <tt>-S</tt> option and this can be either RSA or DSA type. By
default, the signature message digest type is MD5, but any combination
of sign key type and message digest type supported by the OpenSSL
library can be specified using the <tt>-c</tt> option.</p>
<p>The rules say cryptographic media should be generated with proventic
filestamps, which means the host should already be synchronized before
this program is run. This of course creates a chicken-and-egg problem
when the host is started for the first time. Accordingly, the host
time should be set by some other means, such as
eyeball-and-wristwatch, at least so that the certificate lifetime is
within the current year. After that and when the host is synchronized
to a proventic source, the certificate should be re-generated.</p>
<p>Additional information on trusted groups and identity schemes is on
the <a href="autokey.html">Autokey Public-Key Authentication</a>
page.</p>
<h4 id="cmd">Command Line Options</h4>
<dl>
<dt><tt>-b <i>modulus</i></tt></dt>
<dd>Set the modulus for generating identity keys to <i>modulus</i>
bits. The modulus defaults to 256, but can be set from 256 (32
octets) to 2048 (256 octets). Use the larger moduli with caution,
as this can consume considerable computing resources and increases
the size of authenticated packets.</dd>
<dt><tt>-c [ RSA-MD2 | RSA-MD5 | RSA-SHA | RSA-SHA1 | RSA-MDC2 | RSA-RIPEMD160 | DSA-SHA | DSA-SHA1 ]</tt></dt>
<dd>Select certificate digital signature and message digest scheme.
Note that RSA schemes must be used with an RSA sign key and DSA
schemes must be used with a DSA sign key. The default without this
option is <tt>RSA-MD5</tt>. If compatibility with FIPS 140-2 is
required, either the <tt>DSA-SHA</tt> or <tt>DSA-SHA1</tt> scheme
must be used.</dd>
<dt><tt>-C <i>cipher</i></tt></dt>
<dd>Select the OpenSSL cipher to use for password-protected keys.
The <tt>openssl -h</tt> command provided with OpenSSL displays
available ciphers. The default without this option
is <tt>des-ede3-cbc</tt>.</dd>
<dt><tt>-d</tt></dt>
<dd>Enable debugging. This option displays the cryptographic data
produced for eye-friendly billboards.</dd>
<dt><tt>-e</tt></dt>
<dd>Extract the IFF or GQ public parameters from the <tt>IFFkey</tt>
or <tt>GQkey</tt> keys file previously specified. Send the
unencrypted data to the standard output stream <tt>stdout</tt>.</dd>
<dt><tt>-G</tt></dt>
<dd>Generate a new encrypted GQ key file for the Guillou-Quisquater
(GQ) identity scheme. This option is mutually exclusive with
the <tt>-I</tt> and <tt>-V</tt> options.</dd>
<dt><tt>-H</tt></dt>
<dd>Generate a new encrypted RSA public/private host key file.</dd>
<dt><tt>-i <i>group</i></tt></dt>
<dd>Set the optional Autokey group name to <tt><i>group</i></tt>. This
is used in the identity scheme parameter file names. In that role,
the default is the host name if no group is provided. The group
name, if specified using <tt>-i</tt> or using <tt>-s</tt> following
an <tt>@</tt> character, is also used in certificate subject and
issuer names in the form <tt><i>host</i>@<i>group</i></tt> and
should match the group specified via <tt>crypto ident</tt>
or <tt>server ident</tt> in ntpd's configuration file.</dd>
<dt><tt>-I</tt></dt>
<dd>Generate a new encrypted IFF key file for the Schnorr (IFF)
identity scheme. This option is mutually exclusive with
the <tt>-G</tt> and <tt>-V</tt> options.</dd>
<dt><tt>-l <i>days</i></tt></dt>
<dd>Set the lifetime for certificates to <tt><i>days</i></tt>. The
default lifetime is one year (365 d).</dd>
<dt><tt>-m <i>modulus</i></tt></dt>
<dd>Set the modulus for generating files to <i>modulus</i> bits. The
modulus defaults to 512, but can be set from 256 (32 octets) to 2048
(256 octets). Use the larger moduli with caution, as this can
consume considerable computing resources and increases the size of
authenticated packets.</dd>
<dt><tt>-M</tt></dt>
<dd>Generate a new keys file containing 10 MD5 keys and 10 SHA keys.
An MD5 key is a string of 20 random printable ASCII characters,
while a SHA key is a string of 40 random hex digits. The file can be
edited using a text editor to change the key type or key content.
This option is mutually exclusive with all other options.</dd>
<dt><tt>-P</tt></dt>
<dd>Generate a new private certificate used by the PC identity scheme.
By default, the program generates public certificates. Note: the PC
identity scheme is not recommended for new installations.</dd>
<dt><tt>-p <i>passwd</i></tt></dt>
<dd>Set the password for reading and writing encrypted files
to <tt><i>passwd</i></tt>. These include the host, sign and
identify key files. By default, the password is the string returned
by the Unix <tt>gethostname()</tt> routine.</dd>
<dt><tt>-q <i>passwd</i></tt></dt>
<dd>Set the password for writing encrypted IFF, GQ and MV identity
files redirected to <tt>stdout</tt> to <tt><i>passwd</i></tt>=. In
effect, these files are decrypted with the <tt>-p</tt> password,
then encrypted with the <tt>-q</tt> password. By default, the
password is the string returned by the Unix <tt>gethostname()</tt>
routine.</dd>
<dt><tt>-S [ RSA | DSA ]</tt></dt>
<dd>Generate a new encrypted public/private sign key file of the
specified type. By default, the sign key is the host key and has
the same type. If compatibly with FIPS 140-2 is required, the sign
key type must be <tt>DSA</tt>.</dd>
<dt><tt>-s <i>host</i>[@<i>group</i>]</tt></dt>
<dd>Specify the Autokey host name, where <tt><i>host</i></tt> is the
host name and <tt><i>group</i></tt> is the optional group name. The
host name, and if provided, group name are used
in <tt><i>host</i>@<i>group</i></tt> form as certificate subject and
issuer. Specifying <tt>-s @<i>group</i></tt> is allowed, and
results in leaving the host name unchanged, as
with <tt>-i <i>group</i></tt>. The group name, or if no group is
provided, the host name are also used in the file names of IFF, GQ,
and MV identity scheme parameter files. If <tt><i>host</i></tt> is
not specified, the default host name is the string returned by
the <tt>gethostname()</tt> routine.</dd>
<dt><tt>-T</tt></dt>
<dd>Generate a trusted certificate. By default, the program generates
nontrusted certificates.</dd>
<dt><tt>-V <i>nkeys</i></tt></dt>
<dd>Generate <tt>nkeys</tt> encrypted server keys for the
Mu-Varadharajan (MV) identity scheme. This option is mutually
exclusive with the <tt>-I</tt> and <tt>-G</tt> options. Note:
support for this option should be considered a work in
progress.</dd>
</dl>
<h4 id="rand">Random Seed File</h4>
<p>All cryptographically sound key generation schemes must have means to
randomize the entropy seed used to initialize the internal
pseudo-random number generator used by the OpenSSL library routines.
If a site supports <tt>ssh</tt>, it is very likely that means to do
this are already available. The entropy seed used by the OpenSSL
library is contained in a file, usually called <tt>.rnd</tt>, which
must be available when starting the <tt>ntp-keygen</tt> program
or <tt>ntpd</tt> daemon.</p>
<p>The OpenSSL library looks for the file using the path specified by
the <tt>RANDFILE</tt> environment variable in the user home directory,
whether root or some other user. If the <tt>RANDFILE</tt> environment
variable is not present, the library looks for the <tt>.rnd</tt> file
in the user home directory. Since both the <tt>ntp-keygen</tt>
program and <tt>ntpd</tt> daemon must run as root, the logical place
to put this file is in <tt>/.rnd</tt> or <tt>/root/.rnd</tt>. If the
file is not available or cannot be written, the program exits with a
message to the system log.</p>
<h4 id="fmt">Cryptographic Data Files</h4>
<p>File and link names are in the
form <tt>ntpkey_<i>key</i>_<i>name</i>.<i>fstamp</i></tt>,
where <tt><i>key</i></tt> is the key or parameter
type, <tt><i>name</i></tt> is the host or group name
and <tt><i>fstamp</i></tt> is the filestamp (NTP seconds) when the
file was created). By convention, <em><tt>key</tt></em> names in
generated file names include both upper and lower case characters,
while <em><tt>key</tt></em> names in generated link names include only
lower case characters. The filestamp is not used in generated link
names.</p>
<p>The <em><tt>key</tt></em> name is a string defining the cryptographic
key type. Key types include public/private keys <tt>host</tt>
and <tt>sign</tt>, certificate <tt>cert</tt> and several
challenge/response key types. By convention, client files used for
challenges have a <tt>par</tt> subtype, as in the IFF
challenge <tt>IFFpar</tt>, while server files for responses have
a <tt>key</tt> subtype, as in the GQ response <tt>GQkey</tt>.</p>
<p>All files begin with two nonencrypted lines. The first line contains
the file name in the
format <tt>ntpkey_<i>key</i>_<i>host</i>.<i>fstamp</i></tt>. The second
line contains the datestamp in conventional Unix <tt>date</tt> format.
Lines beginning with <tt>#</tt> are ignored.</p>
<p>The remainder of the file contains cryptographic data encoded first
using ASN.1 rules, then encrypted using the DES-CBC algorithm with
given password and finally written in PEM-encoded printable ASCII text
preceded and followed by MIME content identifier lines.</p>
<p>The format of the symmetric keys file, ordinarily
named <tt>ntp.keys,</tt> is somewhat different than the other files in
the interest of backward compatibility. Ordinarily, the file is
generated by this program, but it can be constructed and edited using
an ordinary text editor.</p>
<table>
<caption style="caption-side: bottom;">
Figure 1. Typical Symmetric Key File
</caption>
<tr><td style="border: 1px solid black; border-spacing: 0;">
<pre style="color:grey;">
# ntpkey_MD5key_bk.ntp.org.3595864945
# Thu Dec 12 19:22:25 2013
1 MD5 L";Nw<`.I<f4U0)247"i # MD5 key
2 MD5 &>l0%XXK9O'51VwV<xq~ # MD5 key
3 MD5 lb4zLW~d^!K:]RsD'qb6 # MD5 key
4 MD5 Yue:tL[+vR)M`n~bY,'? # MD5 key
5 MD5 B;fxlKgr/&4ZTbL6=RxA # MD5 key
6 MD5 4eYwa`o}3i@@V@..R9!l # MD5 key
7 MD5 `A.([h+;wTQ|xfi%Sn_! # MD5 key
8 MD5 45:V,r4]l6y^JH6.Sh?F # MD5 key
9 MD5 3-5vcn*6l29DS?Xdsg)* # MD5 key
10 MD5 2late4Me # MD5 key
11 SHA1 a27872d3030a9025b8446c751b4551a7629af65c # SHA1 key
12 SHA1 21bc3b4865dbb9e920902abdccb3e04ff97a5e74 # SHA1 key
13 SHA1 2b7736fe24fef5ba85ae11594132ab5d6f6daba9 # SHA1 key
14 SHA a5332809c8878dd3a5b918819108a111509aeceb # SHA key
15 MD2 2fe16c88c760ff2f16d4267e36c1aa6c926e6964 # MD2 key
16 MD4 b2691811dc19cfc0e2f9bcacd74213f29812183d # MD4 key
17 MD5 e4d6735b8bdad58ec5ffcb087300a17f7fef1f7c # MD5 key
18 MDC2 a8d5e2315c025bf3a79174c87fbd10477de2eabc # MDC2 key
19 RIPEMD160 77ca332cafb30e3cafb174dcd5b80ded7ba9b3d2 # RIPEMD160 key
20 AES128CMAC f92ff73eee86c1e7dc638d6489a04e4e555af878 # AES128CMAC key
21 MD5 sampo 10.1.2.3/24
</pre></td></tr></table>
<p>Figure 1 shows a typical symmetric keys file used by the reference
implementation. Each line of the file contains three or four fields,
first an integer between 1 and 65534, inclusive, representing the key
identifier used in the <tt>server</tt> and <tt>peer</tt> configuration
commands. Second is the key type for the message digest algorithm,
which in the absence of the OpenSSL library must be <tt>MD5</tt> to
designate the MD5 message digest algorithm. If the OpenSSL library is
installed, the key type can be any message digest algorithm supported
by that library. However, if compatibility with FIPS 140-2 is
required, the key type must be either <tt>SHA</tt> or <tt>SHA1</tt>.
The key type can be changed using an ASCII text editor.</p>
<p>The third field is the key.</p>
<p>An MD5 key consists of a printable ASCII string less than or equal to
16 characters and terminated by whitespace or a # character. An
OpenSSL key consists of a hex-encoded ASCII string of 40 characters,
which is truncated as necessary.</p>
<p>Note that the keys used by the <tt>ntpq</tt> and <tt>ntpdc</tt>
programs are checked against passwords requested by the programs and
entered by hand, so it is generally appropriate to specify these keys
in human readable ASCII format.</p>
<p>The optional fourth field is one or more IPs, with each IP separated
with a comma. An IP may end with an optional <tt>/subnetbits</tt>
suffix, which limits the acceptance of the key identifier to packets
claiming to be from the described IP space.</p>
<p>The <tt>ntp-keygen</tt> program generates a MD5 symmetric keys
file <tt>ntpkey_MD5key_<i>hostname.filestamp</i></tt>. Since the file
contains private shared keys, it should be visible only to root and
distributed by secure means to other subnet hosts. The NTP daemon
loads the file <tt>ntp.keys</tt>, so <tt>ntp-keygen</tt> installs a
soft link from this name to the generated file. Subsequently, similar
soft links must be installed by manual or automated means on the other
subnet hosts. While this file is not used with the Autokey Version 2
protocol, it is needed to authenticate some remote configuration
commands used by the <a href="ntpq.html"><tt>ntpq</tt></a>
and <a href="ntpdc.html"><tt>ntpdc</tt></a> utilities.</p>
<h4 id="bug">Bugs</h4>
<p>It can take quite a while to generate some cryptographic values.</p>
<hr>
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