Provided by: ntp_4.2.8p12+dfsg-3ubuntu2_amd64 bug

NAME

     ntp-keygen — Create a NTP host key

SYNOPSIS

     ntp-keygen [-flags] [-flag [value]] [--option-name[[=| ]value]]

                All arguments must be options.

DESCRIPTION

     This program generates cryptographic data files used by the NTPv4 authentication and
     identification 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, signing keys, certificates, and identity keys and parameters used in Autokey public
     key cryptography.  These files are used for cookie encryption, digital signature, and
     challenge/response identification algorithms compatible with the Internet standard security
     infrastructure.

     The message digest symmetric 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 email to other sites and certificate authorities.  By default, files are not
     encrypted.

     When used to generate message digest symmetric 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 SHA1, AES-128-CMAC, and other
     message digest algorithms.  The message digest symmetric 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 ntpq(1) and
     ntpdc(1) utility programs.

     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.

     Some files used by this program are encrypted using a private password.  The -p option
     specifies the read password for local encrypted files and the -q option the write password
     for encrypted files sent to remote sites.  If no password is specified, the host name
     returned by the Unix hostname(1) command, normally the DNS name of the host, is used as the
     the default read password, for convenience.  The ntp-keygen program prompts for the password
     if it reads an encrypted file and the password is missing or incorrect.  If an encrypted
     file is read successfully and no write password is specified, the read password is used as
     the write password by default.

     The pw option of the crypto ntpd(8) configuration command specifies the read password for
     previously encrypted local files.  This must match the local read password used by this
     program.  If not specified, the host name is used.  Thus, if files are generated by this
     program without an explicit password, they can be read back by ntpd(8) without specifying an
     explicit password but only on the same host.  If the write password used for encryption is
     specified as the host name, these files can be read by that host with no explicit password.

     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 ntp.keys, is usually installed in /etc.  Other files and links are usually
     installed in /usr/local/etc, which is normally in a shared filesystem in NFS-mounted
     networks and cannot be changed by shared clients.  In these cases, NFS clients can specify
     the files in another directory such as /etc using the keysdir ntpd(8) configuration file
     command.

     This program directs commentary and error messages to the standard error stream stderr and
     remote files to the standard output stream stdout 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 ntpkey* and include the file type, generating host and filestamp, as
     described in the Cryptographic Data Files section below.

   Running the Program
     The safest way to run the ntp-keygen program is logged in directly as root.  The recommended
     procedure is change to the keys directory, usually /usr/local/etc, then run the program.

     To test and gain experience with Autokey concepts, log in as root and change to the keys
     directory, usually /usr/local/etc.  When run for the first time, or if all files with names
     beginning with ntpkey* have been removed, use the ntp-keygen command without arguments to
     generate a default RSA host key and matching RSA-MD5 certificate file with expiration date
     one year hence, which is all that is necessary in many cases.  The program also generates
     soft links from the generic names to the respective files.  If run again without options,
     the program uses the existing keys and parameters and generates a new certificate file with
     new expiration date one year hence, and soft link.

     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.  When necessary, a
     different sign key can be specified and this can be either RSA or DSA type.  By default, the
     message digest type is MD5, but any combination of sign key type and message digest type
     supported by the OpenSSL library can be specified, including those using the AES128CMAC,
     MD2, MD5, MDC2, SHA, SHA1 and RIPE160 message digest algorithms.  However, the scheme
     specified in the certificate must be compatible with the sign key.  Certificates using any
     digest algorithm are compatible with RSA sign keys; however, only SHA and SHA1 certificates
     are compatible with DSA sign keys.

     Private/public key files and certificates are compatible with other OpenSSL applications and
     very likely other libraries as well.  Certificates or certificate requests derived from them
     should be compatible with extant industry practice, although some users might find the
     interpretation of X509v3 extension fields somewhat liberal.  However, the identification
     parameter files, although encoded as the other files, are probably not compatible with
     anything other than Autokey.

     Running the program as other than root and using the Unix su(1) command to assume root may
     not work properly, since by default the OpenSSL library looks for the random seed file .rnd
     in the user home directory.  However, there should be only one .rnd, most conveniently in
     the root directory, so it is convenient to define the RANDFILE environment variable used by
     the OpenSSL library as the path to .rnd.

     Installing the keys as root might not work in NFS-mounted shared file systems, as NFS
     clients may not be able to write to the shared keys directory, even as root.  In this case,
     NFS clients can specify the files in another directory such as /etc using the keysdir
     ntpd(8) configuration file command.  There is no need for one client to read the keys and
     certificates of other clients or servers, as these data are obtained automatically by the
     Autokey protocol.

     Ordinarily, cryptographic files are generated by the host that uses them, but it is possible
     for a trusted agent (TA) to generate these files for other hosts; however, in such cases
     files should always be encrypted.  The subject name and trusted name default to the hostname
     of the host generating the files, but can be changed by command line options.  It is
     convenient to designate the owner name and trusted name as the subject and issuer fields,
     respectively, of the certificate.  The owner name is also used for the host and sign key
     files, while the trusted name is used for the identity files.

     All files are installed by default in the keys directory /usr/local/etc, which is normally
     in a shared filesystem in NFS-mounted networks.  The actual location of the keys directory
     and each file can be overridden by configuration commands, but this is not recommended.
     Normally, the files for each host are generated by that host and used only by that host,
     although exceptions exist as noted later on this page.

     Normally, files containing private values, including the host key, sign key and
     identification parameters, are permitted root read/write-only; while others containing
     public values are permitted world readable.  Alternatively, files containing private values
     can be encrypted and these files permitted world readable, which simplifies maintenance in
     shared file systems.  Since uniqueness is insured by the hostname and filestamp file name
     extensions, the files for an NTP server and dependent clients can all be installed in the
     same shared directory.

     The recommended practice is to keep the file name extensions when installing a file and to
     install a soft link from the generic names specified elsewhere on this page to the generated
     files.  This allows new file generations to be activated simply by changing the link.  If a
     link is present, ntpd(8) follows it to the file name to extract the filestamp.  If a link is
     not present, ntpd(8) extracts the filestamp from the file itself.  This allows clients to
     verify that the file and generation times are always current.  The ntp-keygen program uses
     the same filestamp extension for all files generated at one time, so each generation is
     distinct and can be readily recognized in monitoring data.

     Run the command on as many hosts as necessary.  Designate one of them as the trusted host
     (TH) using ntp-keygen with the -T 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.

     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 -S 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 -c option.

     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.

     Additional information on trusted groups and identity schemes is on the “Autokey Public-Key
     Authentication” page.

     File names begin with the prefix ntpkey_ and end with the suffix _hostname. filestamp, where
     hostname is the owner name, usually the string returned by the Unix hostname(1) command, and
     filestamp is the NTP seconds when the file was generated, in decimal digits.  This both
     guarantees uniqueness and simplifies maintenance procedures, since all files can be quickly
     removed by a rm ntpkey* command or all files generated at a specific time can be removed by
     a rm *filestamp command.  To further reduce the risk of misconfiguration, the first two
     lines of a file contain the file name and generation date and time as comments.

   Trusted Hosts and Groups
     Each cryptographic configuration involves selection of a signature scheme and identification
     scheme, called a cryptotype, as explained in the Authentication Options section of
     ntp.conf(5).  The default cryptotype uses RSA encryption, MD5 message digest and TC
     identification.  First, configure a NTP subnet including one or more low-stratum trusted
     hosts from which all other hosts derive synchronization directly or indirectly.  Trusted
     hosts have trusted certificates; all other hosts have nontrusted certificates.  These hosts
     will automatically and dynamically build authoritative certificate trails to one or more
     trusted hosts.  A trusted group is the set of all hosts that have, directly or indirectly, a
     certificate trail ending at a trusted host.  The trail is defined by static configuration
     file entries or dynamic means described on the Automatic NTP Configuration Options section
     of ntp.conf(5).

     On each trusted host as root, change to the keys directory.  To insure a fresh fileset,
     remove all ntpkey files.  Then run ntp-keygen -T to generate keys and a trusted certificate.
     On all other hosts do the same, but leave off the -T flag to generate keys and nontrusted
     certificates.  When complete, start the NTP daemons beginning at the lowest stratum and
     working up the tree.  It may take some time for Autokey to instantiate the certificate
     trails throughout the subnet, but setting up the environment is completely automatic.

     If it is necessary to use a different sign key or different digest/signature scheme than the
     default, run ntp-keygen with the -S type option, where type is either RSA or DSA.  The most
     frequent need to do this is when a DSA-signed certificate is used.  If it is necessary to
     use a different certificate scheme than the default, run ntp-keygen with the -c scheme
     option and selected scheme as needed.  If ntp-keygen is run again without these options, it
     generates a new certificate using the same scheme and sign key, and soft link.

     After setting up the environment it is advisable to update certificates from time to time,
     if only to extend the validity interval.  Simply run ntp-keygen with the same flags as
     before to generate new certificates using existing keys, and soft links.  However, if the
     host or sign key is changed, ntpd(8) should be restarted.  When ntpd(8) is restarted, it
     loads any new files and restarts the protocol.  Other dependent hosts will continue as usual
     until signatures are refreshed, at which time the protocol is restarted.

   Identity Schemes
     As mentioned on the Autonomous Authentication page, the default TC identity scheme is
     vulnerable to a middleman attack.  However, there are more secure identity schemes
     available, including PC, IFF, GQ and MV schemes described below.  These schemes are based on
     a TA, one or more trusted hosts and some number of nontrusted hosts.  Trusted hosts prove
     identity using values provided by the TA, while the remaining hosts prove identity using
     values provided by a trusted host and certificate trails that end on that host.  The name of
     a trusted host is also the name of its sugroup and also the subject and issuer name on its
     trusted certificate.  The TA is not necessarily a trusted host in this sense, but often is.

     In some schemes there are separate keys for servers and clients.  A server can also be a
     client of another server, but a client can never be a server for another client.  In
     general, trusted hosts and nontrusted hosts that operate as both server and client have
     parameter files that contain both server and client keys.  Hosts that operate only as
     clients have key files that contain only client keys.

     The PC scheme supports only one trusted host in the group.  On trusted host alice run
     ntp-keygen -P -p password to generate the host key file ntpkey_ RSA key_alice. filestamp and
     trusted private certificate file ntpkey_ RSA-MD5 _ cert_alice. filestamp, and soft links.
     Copy both files to all group hosts; they replace the files which would be generated in other
     schemes.  On each host bob install a soft link from the generic name ntpkey_host_bob to the
     host key file and soft link ntpkey_cert_bob to the private certificate file.  Note the
     generic links are on bob, but point to files generated by trusted host alice.  In this
     scheme it is not possible to refresh either the keys or certificates without copying them to
     all other hosts in the group, and recreating the soft links.

     For the IFF scheme proceed as in the TC scheme to generate keys and certificates for all
     group hosts, then for every trusted host in the group, generate the IFF parameter file.  On
     trusted host alice run ntp-keygen -T -I -p password to produce her parameter file
     ntpkey_IFFpar_alice.filestamp, which includes both server and client keys.  Copy this file
     to all group hosts that operate as both servers and clients and install a soft link from the
     generic ntpkey_iff_alice to this file.  If there are no hosts restricted to operate only as
     clients, there is nothing further to do.  As the IFF scheme is independent of keys and
     certificates, these files can be refreshed as needed.

     If a rogue client has the parameter file, it could masquerade as a legitimate server and
     present a middleman threat.  To eliminate this threat, the client keys can be extracted from
     the parameter file and distributed to all restricted clients.  After generating the
     parameter file, on alice run ntp-keygen -e and pipe the output to a file or email program.
     Copy or email this file to all restricted clients.  On these clients install a soft link
     from the generic ntpkey_iff_alice to this file.  To further protect the integrity of the
     keys, each file can be encrypted with a secret password.

     For the GQ scheme proceed as in the TC scheme to generate keys and certificates for all
     group hosts, then for every trusted host in the group, generate the IFF parameter file.  On
     trusted host alice run ntp-keygen -T -G -p password to produce her parameter file
     ntpkey_GQpar_alice.filestamp, which includes both server and client keys.  Copy this file to
     all group hosts and install a soft link from the generic ntpkey_gq_alice to this file.  In
     addition, on each host bob install a soft link from generic ntpkey_gq_bob to this file.  As
     the GQ scheme updates the GQ parameters file and certificate at the same time, keys and
     certificates can be regenerated as needed.

     For the MV scheme, proceed as in the TC scheme to generate keys and certificates for all
     group hosts.  For illustration assume trish is the TA, alice one of several trusted hosts
     and bob one of her clients.  On TA trish run ntp-keygen -V n -p password, where n is the
     number of revokable keys (typically 5) to produce the parameter file
     ntpkeys_MVpar_trish.filestamp and client key files ntpkeys_MVkeyd _ trish. filestamp where d
     is the key number (0 < d < n).  Copy the parameter file to alice and install a soft link
     from the generic ntpkey_mv_alice to this file.  Copy one of the client key files to alice
     for later distribution to her clients.  It does not matter which client key file goes to
     alice, since they all work the same way.  Alice copies the client key file to all of her
     clients.  On client bob install a soft link from generic ntpkey_mvkey_bob to the client key
     file.  As the MV scheme is independent of keys and certificates, these files can be
     refreshed as needed.

   Command Line Options
     -b --imbits= modulus
             Set the number of bits in the identity modulus for generating identity keys to
             modulus bits.  The number of bits in the identity modulus defaults to 256, but can
             be set to values from 256 to 2048 (32 to 256 octets).  Use the larger moduli with
             caution, as this can consume considerable computing resources and increases the size
             of authenticated packets.

     -c --certificate= scheme
             Select certificate signature encryption/message digest scheme.  The scheme can be
             one of the following: RSA-MD2, RSA-MD5, RSA-MDC2, RSA-SHA, RSA-SHA1, RSA-RIPEMD160,
             DSA-SHA, or DSA-SHA1.  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
             RSA-MD5.  If compatibility with FIPS 140-2 is required, either the DSA-SHA or
             DSA-SHA1 scheme must be used.

     -C --cipher= cipher
             Select the OpenSSL cipher to encrypt the files containing private keys.  The default
             without this option is three-key triple DES in CBC mode, des-ede3-cbc.  The openssl
             -h command provided with OpenSSL displays available ciphers.

     -d --debug-level
             Increase debugging verbosity level.  This option displays the cryptographic data
             produced in eye-friendly billboards.

     -D --set-debug-level= level
             Set the debugging verbosity to level.  This option displays the cryptographic data
             produced in eye-friendly billboards.

     -e --id-key
             Write the IFF or GQ public parameters from the IFFkey or GQkey client keys file
             previously specified as unencrypted data to the standard output stream stdout.  This
             is intended for automatic key distribution by email.

     -G --gq-params
             Generate a new encrypted GQ parameters and key file for the Guillou-Quisquater (GQ)
             identity scheme.  This option is mutually exclusive with the -I and -V options.

     -H --host-key
             Generate a new encrypted RSA public/private host key file.

     -I --iffkey
             Generate a new encrypted IFF key file for the Schnorr (IFF) identity scheme.  This
             option is mutually exclusive with the -G and Fl V options.

     -i --ident= group
             Set the optional Autokey group name to group.  This is used in the identity scheme
             parameter file names of IFF, GQ, and MV client parameters files.  In that role, the
             default is the host name if no group is provided.  The group name, if specified
             using -i or -s following an ‘@’ character, is also used in certificate subject and
             issuer names in the form host @ group and should match the group specified via
             crypto ident or server ident in the ntpd configuration file.

     -l --lifetime= days
             Set the lifetime for certificate expiration to days.  The default lifetime is one
             year (365 days).

     -m --modulus= bits
             Set the number of bits in the prime modulus for generating files to bits.  The
             modulus defaults to 512, but can be set from 256 to 2048 (32 to 256 octets).  Use
             the larger moduli with caution, as this can consume considerable computing resources
             and increases the size of authenticated packets.

     -M --md5key
             Generate a new symmetric keys file containing 10 MD5 keys, and if OpenSSL is
             available, 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.

     -p --password= passwd
             Set the password for reading and writing encrypted files to passwd.  These include
             the host, sign and identify key files.  By default, the password is the string
             returned by the Unix hostname command.

     -P --pvt-cert
             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.

     -q --export-passwd= passwd
             Set the password for writing encrypted IFF, GQ and MV identity files redirected to
             stdout to passwd.  In effect, these files are decrypted with the -p password, then
             encrypted with the -q password.  By default, the password is the string returned by
             the Unix hostname command.

     -s --subject-key= file ... [host] [@ group]
             Specify the Autokey host name, where host is the optional host name and group is the
             optional group name.  The host name, and if provided, group name are used in host @
             group form as certificate subject and issuer.  Specifying -s -@ group is allowed,
             and results in leaving the host name unchanged, as with -i group.  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 client parameter files.  If host is not specified, the
             default host name is the string returned by the Unix hostname command.

     -S --sign-key= [RSA | DSA]
             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 compatibility with
             FIPS 140-2 is required, the sign key type must be DSA.

     -T --trusted-cert
             Generate a trusted certificate.  By default, the program generates a non-trusted
             certificate.

     -V --mv-params nkeys
             Generate nkeys encrypted server keys and parameters for the Mu-Varadharajan (MV)
             identity scheme.  This option is mutually exclusive with the -I and -G options.
             Note: support for this option should be considered a work in progress.

   Random Seed File
     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 library
     routines.  The OpenSSL library uses a designated random seed file for this purpose.  The
     file must be available when starting the NTP daemon and ntp-keygen program.  If a site
     supports OpenSSL or its companion OpenSSH, it is very likely that means to do this are
     already available.

     It is important to understand that entropy must be evolved for each generation, for
     otherwise the random number sequence would be predictable.  Various means dependent on
     external events, such as keystroke intervals, can be used to do this and some systems have
     built-in entropy sources.  Suitable means are described in the OpenSSL software
     documentation, but are outside the scope of this page.

     The entropy seed used by the OpenSSL library is contained in a file, usually called .rnd,
     which must be available when starting the NTP daemon or the ntp-keygen program.  The NTP
     daemon will first look for the file using the path specified by the randfile subcommand of
     the crypto configuration command.  If not specified in this way, or when starting the
     ntp-keygen program, the OpenSSL library will look for the file using the path specified by
     the RANDFILE environment variable in the user home directory, whether root or some other
     user.  If the RANDFILE environment variable is not present, the library will look for the
     .rnd file in the user home directory.  Since both the ntp-keygen program and ntpd(8) daemon
     must run as root, the logical place to put this file is in /.rnd or /root/.rnd.  If the file
     is not available or cannot be written, the daemon exits with a message to the system log and
     the program exits with a suitable error message.

   Cryptographic Data Files
     All file formats begin with two nonencrypted lines.  The first line contains the file name,
     including the generated host name and filestamp, in the format ntpkey_key _ name. filestamp,
     where key is the key or parameter type, name is the host or group name and filestamp is the
     filestamp (NTP seconds) when the file was created.  By convention, key names in generated
     file names include both upper and lower case characters, while key names in generated link
     names include only lower case characters.  The filestamp is not used in generated link
     names.  The second line contains the datestamp in conventional Unix date format.  Lines
     beginning with ‘#’ are considered comments and ignored by the ntp-keygen program and ntpd(8)
     daemon.

     The remainder of the file contains cryptographic data, encoded first using ASN.1 rules, then
     encrypted if necessary, and finally written in PEM-encoded printable ASCII text, preceded
     and followed by MIME content identifier lines.

     The format of the symmetric keys file, ordinarily named ntp.keys, 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.

                            # 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;fx'Kgr/&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
           Figure 1. Typical Symmetric Key File

     Figure 1 shows a typical symmetric keys file used by the reference implementation.
     Following the header the keys are entered one per line in the format
           keyno type key
     where keyno is a positive integer in the range 1-65535; type is the key type for the message
     digest algorithm, which in the absence of the OpenSSL library must be MD5 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 SHA or SHA1; key is the key itself, which is
     a printable ASCII string 20 characters or less in length: each character is chosen from the
     93 printable characters in the range 0x21 through 0x7e ( ‘’!  through ‘~’ ) excluding space
     and the ‘#’ character, 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.

     Note that the keys used by the ntpq(1) and ntpdc(1) 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.

     The ntp-keygen program generates a symmetric keys file ntpkey_MD5key_hostname.filestamp.
     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 ntp.keys,
     so ntp-keygen 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 ntpq(1) and ntpdc(1) utilities.

OPTIONS

     -b imbits, --imbits=imbits
                 identity modulus bits.  This option takes an integer number as its argument.
                 The value of imbits is constrained to being:
                     in the range  256 through 2048

                 The number of bits in the identity modulus.  The default is 256.

     -c scheme, --certificate=scheme
                 certificate scheme.

                 scheme is one of RSA-MD2, RSA-MD5, RSA-MDC2, RSA-SHA, RSA-SHA1, RSA-RIPEMD160,
                 DSA-SHA, or DSA-SHA1.

                 Select the certificate signature encryption/message digest scheme.  Note that
                 RSA schemes must be used with a RSA sign key and DSA schemes must be used with a
                 DSA sign key.  The default without this option is RSA-MD5.

     -C cipher, --cipher=cipher
                 privatekey cipher.

                 Select the cipher which is used to encrypt the files containing private keys.
                 The default is three-key triple DES in CBC mode, equivalent to "-C
                 des-ede3-cbc".  The openssl tool lists ciphers available in "openssl -h" output.

     -d, --debug-level
                 Increase debug verbosity level.  This option may appear an unlimited number of
                 times.

     -D number, --set-debug-level=number
                 Set the debug verbosity level.  This option may appear an unlimited number of
                 times.  This option takes an integer number as its argument.

     -e, --id-key
                 Write IFF or GQ identity keys.

                 Write the public parameters from the IFF or GQ client keys to the standard
                 output.  This is intended for automatic key distribution by email.

     -G, --gq-params
                 Generate GQ parameters and keys.

                 Generate parameters and keys for the GQ identification scheme, obsoleting any
                 that may exist.

     -H, --host-key
                 generate RSA host key.

                 Generate new host keys, obsoleting any that may exist.

     -I, --iffkey
                 generate IFF parameters.

                 Generate parameters for the IFF identification scheme, obsoleting any that may
                 exist.

     -i group, --ident=group
                 set Autokey group name.

                 Set the optional Autokey group name to name.  This is used in the file name of
                 IFF, GQ, and MV client parameters files.  In that role, the default is the host
                 name if this option is not provided.  The group name, if specified using
                 -i/--ident or using -s/--subject-name following an '@' character, is also a part
                 of the self-signed host certificate subject and issuer names in the form
                 host@group and should match the ´crypto ident' or 'server ident' configuration
                 in the ntpd configuration file.

     -l lifetime, --lifetime=lifetime
                 set certificate lifetime.  This option takes an integer number as its argument.

                 Set the certificate expiration to lifetime days from now.

     -m modulus, --modulus=modulus
                 prime modulus.  This option takes an integer number as its argument.  The value
                 of modulus is constrained to being:
                     in the range  256 through 2048

                 The number of bits in the prime modulus.  The default is 512.

     -M, --md5key
                 generate symmetric keys.

                 Generate symmetric keys, obsoleting any that may exist.

     -P, --pvt-cert
                 generate PC private certificate.

                 Generate a private certificate.  By default, the program generates public
                 certificates.

     -p passwd, --password=passwd
                 local private password.

                 Local files containing private data are encrypted with the DES-CBC algorithm and
                 the specified password.  The same password must be specified to the local ntpd
                 via the "crypto pw password" configuration command.  The default password is the
                 local hostname.

     -q passwd, --export-passwd=passwd
                 export IFF or GQ group keys with password.

                 Export IFF or GQ identity group keys to the standard output, encrypted with the
                 DES-CBC algorithm and the specified password.  The same password must be
                 specified to the remote ntpd via the "crypto pw password" configuration command.
                 See also the option --id-key (-e) for unencrypted exports.

     -s host@group, --subject-name=host@group
                 set host and optionally group name.

                 Set the Autokey host name, and optionally, group name specified following an '@'
                 character.  The host name is used in the file name of generated host and signing
                 certificates, without the group name.  The host name, and if provided, group
                 name are used in host@group form for the host certificate subject and issuer
                 fields.  Specifying '-s @group' is allowed, and results in leaving the host name
                 unchanged while appending @group to the subject and issuer fields, as with -i
                 group.  The group name, or if not provided, the host name are also used in the
                 file names of IFF, GQ, and MV client parameter files.

     -S sign, --sign-key=sign
                 generate sign key (RSA or DSA).

                 Generate a new sign key of the designated type, obsoleting any that may exist.
                 By default, the program uses the host key as the sign key.

     -T, --trusted-cert
                 trusted certificate (TC scheme).

                 Generate a trusted certificate.  By default, the program generates a non-trusted
                 certificate.

     -V num, --mv-params=num
                 generate <num> MV parameters.  This option takes an integer number as its
                 argument.

                 Generate parameters and keys for the Mu-Varadharajan (MV) identification scheme.

     -v num, --mv-keys=num
                 update <num> MV keys.  This option takes an integer number as its argument.

                 This option has not been fully documented.

     -?, --help  Display usage information and exit.

     -!, --more-help
                 Pass the extended usage information through a pager.

     -> [cfgfile], --save-opts [=cfgfile]
                 Save the option state to cfgfile.  The default is the last configuration file
                 listed in the OPTION PRESETS section, below.  The command will exit after
                 updating the config file.

     -< cfgfile, --load-opts=cfgfile, --no-load-opts
                 Load options from cfgfile.  The no-load-opts form will disable the loading of
                 earlier config/rc/ini files.  --no-load-opts is handled early, out of order.

     --version [{v|c|n}]
                 Output version of program and exit.  The default mode is `v', a simple version.
                 The `c' mode will print copyright information and `n' will print the full
                 copyright notice.

OPTION PRESETS

     Any option that is not marked as not presettable may be preset by loading values from
     configuration ("RC" or ".INI") file(s) and values from environment variables named:
       NTP_KEYGEN_<option-name> or NTP_KEYGEN
     The environmental presets take precedence  (are  processed  later  than)  the  configuration
     files.   The  homerc  files are "$HOME", and ".".  If any of these are directories, then the
     file .ntprc is searched for within those directories.

USAGE

ENVIRONMENT

     See OPTION PRESETS for configuration environment variables.

FILES

     See OPTION PRESETS for configuration files.

EXIT STATUS

     One of the following exit values will be returned:

     0  (EXIT_SUCCESS)
                   Successful program execution.

     1  (EXIT_FAILURE)
                   The operation failed or the command syntax was not valid.

     66  (EX_NOINPUT)
                   A specified configuration file could not be loaded.

     70  (EX_SOFTWARE)
                   libopts had an internal operational error.  Please report it to
                   autogen-users@lists.sourceforge.net.  Thank you.

AUTHORS

     The University of Delaware and Network Time Foundation

COPYRIGHT

     Copyright (C) 1992-2017 The University of Delaware and Network Time Foundation all rights
     reserved.  This program is released under the terms of the NTP license,
     <http://ntp.org/license>.

BUGS

     It can take quite a while to generate some cryptographic values.

     Please report bugs to http://bugs.ntp.org .

     Please send bug reports to: http://bugs.ntp.org, bugs@ntp.org

NOTES

     Portions of this document came from FreeBSD.

     This manual page was AutoGen-erated from the ntp-keygen option definitions.