ntp-keygen

Generate cryptographic data files used by NTPv4

Syntax:

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

Runs on:

QNX Neutrino


DESCRIPTION
       This  program  generates  cryptographic  data  files  used by the NTPv4
       authentication and identification schemes.  It generates MD5 key  files
       used  in symmetric key cryptography.  In addition, if the OpenSSL soft-
       ware library has been installed, it  generates  keys,  certificate  and
       identity  files  used in public key cryptography.  These files are used
       for cookie encryption, digital signature and challenge/response identi-
       fication  algorithms compatible with the Internet standard security in-
       frastructure.

       All files are in PEM-encoded printable ASCII format,  so  they  can  be
       embedded  as  MIME  attachments  in mail to other sites and certificate
       authorities.  By default, files are not encrypted.

       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 and other message digest algo-
       rithms.   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 ntpq(1) and ntpdc(1) utility programs.

       The remaining generated files are compatible with other OpenSSL  appli-
       cations  and other Public Key Infrastructure (PKI) resources.  Certifi-
       cates 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 password for local encrypted files and  the
       -q option the password for encrypted files sent to remote sites.  If no
       password is specified, the host name returned by the Unix gethostname()
       function, normally the DNS name of the host is used.

       The  pw  option  of the crypto 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  pass-
       word,  they  can  be read back by ntpd without password but only on the
       same host.

       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  usu-
       ally 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.  The location of the
       keys directory can be changed by the keysdir configuration  command  in
       such cases.  Normally, this is in /etc.

       This  program  directs  commentary  and  error messages to the standard
       error stream stderr and remote files to the standard output stream std-
       out  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
       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  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.

       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  con-
       figure  it to synchronize from reliable Internet servers.  Then config-
       ure the other hosts to synchronize to the TH directly or indirectly.  A
       certificate  trail  is created when Autokey asks the immediately ascen-
       dant host towards the TH to sign its certificate, which  is  then  pro-
       vided  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 signa-
       ture message digest type is MD5, but any combination of sign  key  type
       and  message digest type supported by the OpenSSL library can be speci-
       fied 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-gener-
       ated.

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

       The ntpd(1) configuration command crypto pw password specifies the read
       password for previously encrypted files.  The  daemon  expires  on  the
       spot  if  the  password is missing or incorrect.  For convenience, if a
       file has been previously encrypted, the default read  password  is  the
       name  of  the host running the program.  If the previous write password
       is specified as the host name, these files can be  read  by  that  host
       with no explicit password.

       File  names  begin  with  the  prefix  ntpkey_ and end with the postfix
       _hostname.filestamp, where hostname is  the  owner  name,  usually  the
       string returned by the Unix gethostname() routine, 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  gen-
       erated  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.

       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
       file  name extensions, the files for a NFS 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 follows it  to  the  file  name  to  extract  the
       filestamp.   If  a  link is not present, ntpd(1) 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 timestamp extension for all files generated at one time,  so  each
       generation  is  distinct  and  can  be readily recognized in monitoring
       data.

   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, usu-
       ally /usr/local/etc, then run the program.   When  run  for  the  first
       time, or if all ntpkey files have been removed, the program generates a
       RSA host key file and matching RSA-MD5 certificate file, 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, the pro-
       gram  uses the same host key file, but generates a new certificate file
       and 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 speci-
       fied  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, includ-
       ing those using the MD2, MD5,  SHA,  SHA1,  MDC2  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.  Certifi-
       cates 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 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.   How-
       ever,  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  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
       file  name extensions, the files for a NFS 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 follows it  to  the  file  name  to  extract  the
       filestamp.   If  a  link is not present, ntpd(1) 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 timestamp extension for all files generated at one time,  so  each
       generation  is  distinct  and  can  be readily recognized in monitoring
       data.

   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, usu-
       ally /usr/local/etc, then run the program.   When  run  for  the  first
       time, or if all ntpkey files have been removed, the program generates a
       RSA host key file and matching RSA-MD5 certificate file, 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, the pro-
       gram  uses the same host key file, but generates a new certificate file
       and 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 speci-
       fied  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, includ-
       ing those using the MD2, MD5,  SHA,  SHA1,  MDC2  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.  Certifi-
       cates 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 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.   How-
       ever,  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  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.  seconds.  seconds.  s
       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  certifi-
       cate  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 Configura-
       tion 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  cer-
       tificates.   When complete, start the NTP daemons beginning at the low-
       est stratum and working up the tree.  It may take some time for Autokey
       to  instantiate  the certificate trails throughout the subnet, but set-
       ting up the environment is completely automatic.

       If it is necessary to use a different sign key or different digest/sig-
       nature scheme than the default, run ntp-keygen with the -S type option,
       where type is either RSA or DSA.  The most often 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.  f ntp-keygen is run
       again without these options, it generates a new certificate  using  the
       same scheme and sign key.

       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.  However, if the host  or  sign  key  is  changed,
       ntpd(1)  should  be restarted.  When ntpd(1) is restarted, it loads any
       new files and restarts the protocol.  Other dependent hosts  will  con-
       tinue as usual until signatures are refreshed, at which time the proto-
       col 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  described  on the "Identification Schemes" page (maybe available at
       http://www.eecis.udel.edu/%7emills/keygen.html).   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 non-
       trusted 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_RSAkey_alice.filestamp and trusted private certificate file ntp-
       key_RSA-MD5_cert_alice.filestamp.   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  cer-
       tificate  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.

       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_IFF-
       par_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 mail
       program.  Copy or mail 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 cer-
       tificates 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   ntp-
       key_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  ntp-
       keys_MVpar_trish.filestamp     and     client     key     files    ntp-
       keys_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 doesn't 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 cliens.  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
       -c scheme
              Select certificate message digest/signature  encryption  scheme.
              The  scheme can be one of the following: or DSA-SHA1.  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.

       -d     Enable debugging.  This option displays the  cryptographic  data
              produced in eye-friendly billboards.

       -e     Write  the  IFF  client  keys  to  the standard output.  This is
              intended for automatic key distribution by mail.

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

       -g     Generate  keys for the GQ identification scheme using the exist-
              ing GQ parameters.  If the GQ parameters do not yet exist,  cre-
              ate them first.

       -H     Generate new host keys, obsoleting any that may exist.

       -I     Generate  parameters for the IFF identification scheme, obsolet-
              ing any that may exist.

       -i name
              Set the suject name to name.  This is used as the subject  field
              in certificates and in the file name for host and sign keys.

       -M     Generate MD5 keys, obsoleting any that may exist.

       -P     Generate  a private certificate.  By default, the program gener-
              ates public certificates.

       -p password
              Encrypt generated files containing private  data  with  password
              and the DES-CBC algorithm.

       -q     Set the password for reading files to password.

       -S [RSA | 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.

       -s name
              Set  the issuer name to name.  This is used for the issuer field
              in certificates and in the file name for identity files.

       -T     Generate a trusted certificate.  By default, the program  gener-
              ates a non-trusted certificate.

       -V nkeys
              Generate  parameters and keys for the Mu-Varadharajan (MV) iden-
              tification scheme.

   Random Seed File
       All cryptographically sound key generation schemes must have  means  to
       randomize  the entropy seed used to initialize the internal pseudo-ran-
       dom 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 pre-
       dictable.  Various means dependent on external  events,  such  as  key-
       stroke 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 dae-
       mon  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.  If the file is not available or  can-
       not  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 other file formats begin with two lines.  The  first  contains  the
       file name, including the generated host name and filestamp.  The second
       contains the datestamp in conventional Unix date format.  Lines  begin-
       ning  with # are considered comments and ignored by the ntp-keygen pro-
       gram and ntpd(1) daemon.  Cryptographic values are encoded first  using
       ASN.1  rules,  then  encrypted  if  necessary, and finally written PEM-
       encoded printable ASCII format preceded and followed  by  MIME  content
       identifier lines.

       The  format  of  the symmetric keys file is somewhat different than the
       other files in the interest of backward compatibility.   Since  DES-CBC
       is deprecated in NTPv4, the only key format of interest is MD5 alphanu-
       meric strings.  Following hte heard the keys are entered one  per  line
       in the format
           keyno type key
       where  keyno  is  a positive integer in the range 1-65,535, type is the
       string MD5 defining the key format and key is the key itself, which  is
       a printable ASCII string 16 characters or less in length.  Each charac-
       ter is chosen from the  93  printable  characters  in  the  range  0x21
       through 0x7f excluding space and the '#' character.

       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  MD5  symmetric  keys  file  ntp-
       key_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.  Sub-
       sequently,  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-SHA, RSA-SHA1, RSA-MDC2,
              RSA-RIPEMD160, DSA-SHA, or DSA-SHA1.

              Select the certificate message digest/signature encryption
              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 "@code{-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 unlim-
              ited number of times.  This option takes an integer number as
              its argument.


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

              Write the IFF or GQ client keys to the standard output.  This is
              intended for automatic key distribution by mail.

       -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, obsolet-
              ing 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's subject and issuer
              names in the form host@group and should match the ntpd's config-
              uration 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, --md5key
              generate MD5 keys.

              Generate MD5 keys, obsoleting any that may exist.

       -m modulus, --modulus=modulus
              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.

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

              Generate a private certificate.  By default, the program gener-
              ates 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 host-
              name.

       -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 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.

       -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's subject and issuer
              fields.  Specifying '-s @group' is allowed, and results in leav-
              ing the host name unchanged while appending @group to the sub-
              ject 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.

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

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

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

              Generate parameters and keys for the Mu-Varadharajan (MV) iden-
              tification 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 con-
              figuration 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 load-
       ing 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
       The -p password option specifies the write  password  and  -q  password
       option  the read password for previously encrypted files.  The ntp-key-
       gen 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.

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

BUGS
       It can take quite a while to generate some cryptographic  values,  from
       one to several minutes with modern architectures such as UltraSPARC and
       up to tens of minutes to an hour with older architectures such as SPARC
       IPC.

       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.