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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>
    <br clear="left">
    <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&lt;`.I&lt;f4U0)247"i  # MD5 key
	    2  MD5 &amp;&gt;l0%XXK9O'51VwV&lt;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/&amp;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>
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