ntp.keys - Network Time Protocol (NTP) authentication key
file
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 identical between a set of peers
sharing the same key number.
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
Conventional name of the key file
Commands: ntpdate(8), ntpq(8), xntpd(8), xntpdc(8)
Files: ntp.conf(4)
Network Administration: Services delim off
ntp.keys(4)
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