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NTP_KEYS(5) File Formats Manual (file) NTP_KEYS(5)


ntp.keysNTP symmetric key file format


ntp.keysNTP symmetric key file format


ntp.keys [--option-name] [--option-name value]

All arguments must be options.


This document describes the format of an NTP symmetric key file. For a description of the use of this type of file, see the "Authentication Support" section of the ntp.conf(5) page.

ntpd(8) reads its keys from a file specified using the -k command line option or the keys statement in the configuration file. While key number 0 is fixed by the NTP standard (as 56 zero bits) and may not be changed, one or more keys numbered between 1 and 65535 may be arbitrarily set in the keys file.

The key file uses the same comment conventions as the configuration file. Key entries use a fixed format of the form

keyno type key opt_IP_list

where keyno is a positive integer (between 1 and 65535), type is the message digest algorithm, key is the key itself, and opt_IP_list is an optional comma-separated list of IPs where the keyno should be trusted. that are allowed to serve time. Each IP in opt_IP_list may contain an optional /subnetbits specification which identifies the number of bits for the desired subnet of trust. If opt_IP_list is empty, any properly-authenticated message will be accepted.

The key may be given in a format controlled by the type field. The type MD5 is always supported. If ntpd was built with the OpenSSL library then any digest library supported by that library may be specified. However, if compliance with FIPS 140-2 is required the type must be either SHA or SHA1.

What follows are some key types, and corresponding formats:

The key is 1 to 16 printable characters terminated by an EOL, whitespace, or a # (which is the "start of comment" character).

The key is a hex-encoded ASCII string of 40 characters, which is truncated as necessary.

Note that the keys used by the ntpq(8) and ntpdc(8) programs are checked against passwords requested by the programs and entered by hand, so it is generally appropriate to specify these keys in ASCII format.


Display usage information and exit.
Pass the extended usage information through a pager.
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.


Any option that is not marked as not presettable may be preset by loading values from environment variables named:

  NTP_KEYS_<option-name> or NTP_KEYS


See OPTION PRESETS for configuration environment variables.


the default name of the configuration file


One of the following exit values will be returned:

Successful program execution.
The operation failed or the command syntax was not valid.
libopts had an internal operational error. Please report it to Thank you.


ntp.conf(5), ntpd(8), ntpdate(8), ntpdc(1), sntp(1)


The University of Delaware and Network Time Foundation


Copyright (C) 1992-2020 The University of Delaware and Network Time Foundation all rights reserved. This program is released under the terms of the NTP license, <>.


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This document was derived from FreeBSD.

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

June 23 2020 FreeBSD 11.2-RELEASE_SI