The keys file contains a list of numeric key IDs and
key values. These IDs and values are used to verify
that mode 6 and mode 7 NTP packets should be processed.
For example, when running the xntpdc program, you must
supply a valid key ID in response to the
Keyid prompt and its associated key value in response to
the Password prompt. See
``Further examples of NTP''
for sample displays of this.
In addition to a key ID and its associated value, each
entry also contains a one-letter code indicating the type of
the key value. The precise format of an entry in the key file is:
key_ID key_type key_value
The three fields shown above are separated by any combination of
blanks and tabs. Comments may appear on any line and must begin with
the number sign (#).
The fields are:
key ID, which is an arbitrary, unsigned 32-bit number,
written in decimal.
The range of possible values is zero through 4,294,967,295.
Key IDs are specified by the
requestkey and controlkey
statements in the configuration file.
key type, which identifies the type of key_value.
Only one key format, ``M'', is currently supported. This
indicates that the MD5 authentication scheme is being used.
In this case, the key is a one-to-eight-character ASCII string.
The one-letter code for this type is ``M''.
key value, which is
a 56-bit DES encryption key that is written as 8 octets.
The key value always uses odd parity.
Note that you will find it easier to specify ASCII key
values, particularly for keys that are used to verify
xntpdc requests. Because this file contains
authorization data, you are strongly urged to limit
read permission for this file. In particular,
you should remove read permission for other.