Model: MTS200 (1U)
Doc. Ref. no. : m08/om/201
Issue no. : 03
User’s Manual
Page 124 of 195
Page 124 of 195
When authentication is specified, a message authentication code (MAC) is appended to the NTP packet
header. The MAC consists of a 32 bit key identifier (key ID) followed by a 128- or 160 bit message digest.
On receive, the message digest is computed and compared with transmitted MAC. The packet is
accepted only if two MACs are identical.
MTS200 provides support for Symmetric key mechanism based NTP authentication using user define key
ID and key password. MTS200 supports only MD5 Key. MTS200 uses ntp.keys file to store the key ID
and key password. However, the password should be transferred to ntp clients using secure means.
Below is truncated part of ntp.keys file format:
#ntp.keys
1
M
masibus
2
M
test1
3
M
key1
M refers to MD5 key notation.
User can add or replace existing key string using console based configuration utility or webserver. User
can add 1 to 9999 key ID values in MTS200 and key string of max. 20 characters only. Factory default
key id will be set at ID number 1 and Key string “masibus”.
ntp driver will authenticate the ntp messages with symmetric key for only those keys which are defined as
trustedkey in ntp.conf file. This can be also be done using console based configuration utility and
webserver mode. Remember, the trustedkey should be one of the keys defined in ntp.keys file, failing to
which ntp association between MTS200 and ntp clients will not complete.
Also, for successful NTP secure communication between MTS200 and ntp clients, it is necessary to
define same key ID and key string in ntp.keys file in ntp client device. Apart from adding key ID and string
in clients ntp.keys file, same key ID has to be defined in client ntp.conf file as trustedkey.
Using Console based configuration utility:
Refer section 9.2.2 for method to edit NTP symmetric key and add/delete trusted key using console
based configuration utility.
Using Webserver:
1. For editing NTP symmetric key file ntp.keys, go to Security page -
> “NTP Symmetric Key” section in
below image.
In this section, enter Key id number in field “Key ID” and password in field “Key String” and then click on
“ADD” button. This will add key in ntp.keys file. To check the existing or new added keys, click on “View
Symm. Keys” button.
