--- name: "ntp.keys" section: "5" platform: "linux" package: "ntp" version: "4.2.8.p18-6" release: "Arch Linux 2026-11-01" platforms: ["linux", "freebsd"] url: "https://new.carta.tech/ntp.keys" --- # ntp.keys(5) NTP symmetric key file format ntp.keys - NTP symmetric key file format configuration file \[--option-name\] \[--option-name value\] 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: MD5 The key is 1 to 16 printable characters terminated by an EOL, whitespace, or a # (which is the "start of comment" character). SHA SHA1 RMD160 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. /etc/ntp.keys the default name of the configuration file ntp.conf(5), ntpd(1), ntpdate(1), ntpdc(1), sntp(1) The University of Delaware and Network Time Foundation Copyright (C) 1992-2024 The University of Delaware and Network Time Foundation all rights reserved. This program is released under the terms of the NTP license, \. Please send bug reports to: https://bugs.ntp.org, bugs@ntp.org This document was derived from FreeBSD. This manual page was AutoGen-erated from the ntp.keys option definitions. ## NAME **ntp.keys** – NTP symmetric key file format ntp.keys - NTP symmetric key file format configuration file \[**--option-name**\] \[**--option-name** *value*\] 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)](/ntp.conf/5.md) page. [`ntpd`(8)](/ntpd/8.md) 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: `MD5` The key is 1 to 16 printable characters terminated by an EOL, whitespace, or a `#` (which is the "start of comment" character). `SHA`\ `SHA1`\ `RMD160` 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)](/ntpq/8.md) and [`ntpdc`(8)](/ntpdc/8.md) 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. */etc/ntp.keys* the default name of the configuration file [`ntp.conf`(5)](/ntp.conf/5.md), [`ntpd`(1)](/ntpd/1.md), [`ntpdate`(1)](/ntpdate/1.md), [`ntpdc`(1)](/ntpdc/1.md), [`sntp`(1)](/sntp/1.md) The University of Delaware and Network Time Foundation Copyright (C) 1992-2024 The University of Delaware and Network Time Foundation all rights reserved. This program is released under the terms of the NTP license, \. Please send bug reports to: https://bugs.ntp.org, bugs@ntp.org This document was derived from FreeBSD. This manual page was *AutoGen*-erated from the **ntp.keys** option definitions.