ntp.keys(4)ntp.keys(4)NAMEntp.keys - Network Time Protocol (NTP) authentication key file
DESCRIPTION
The NTP standard specifies an extension to allow verification of the
authenticity of received NTP packets and to provide an indication of
authenticity in outgoing packets. This is implemented in xntpd using
the MD5 algorithm to compute the message-digest. The specification
allows any one of possibly 4 billion keys, numbered with 32-bit key
identifiers, to be used to authenticate an association. The servers
involved in an association must agree on the key and key identifier
used to authenticate their data, though they must each learn the key
and key identifier independently. In MD5, the keys are 64 bits (8
bytes). The xntpd daemon 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 of the keys numbered 1
through 15 may be arbitrarily set in the keys file.
One of the keys may be chosen, by way of the configuration file
requestkey statement, to authenticate run time configuration requests
made using the xntpdc(8) program. The latter program obtains the key
from the terminal as a password, so it is generally appropriate to
specify the key chosen to be used for this purpose in ASCII format.
The NTP key file uses the same comment conventions as the configuration
file. Key entries use a fixed format of the form: keyno type key
In this format: Is a positive integer. Is a single character that
defines the format the key is given in. This is always M, representing
Message Digest (MD5) on Tru64 UNIX systems. Is the key itself. The
MD5 algorithm key is a 1-to-8 character ASCII string. Because of the
simple tokenizing routine, you cannot use the following characters in
an ASCII key: " " (space), "#" (number sign), "", "0, and " ". Note
that both the keys and the authentication scheme (MD5) must be identi‐
cal between a set of peers sharing the same key number.
EXAMPLES
The following sample key file shows two defined NTP keys: 2 M
RIrop8KPPvQvYotM # MD5 key as a random ASCII string 14 M sundial
# MD5 key as an ASCII string
FILES
Conventional name of the key file
RELATED INFORMATION
Commands: ntpdate(8), ntpq(8), xntpd(8), xntpdc(8)
Files: ntp.conf(4)
Network Administration: Services delim off
ntp.keys(4)
