The value of tmnxNtpAuthKey is the actual valued compared
by other network elements to authenticate an NTP packet.
The key can be any combination of up to 32 ASCII characters,
including spaces. For authentication to succeed both the
authentication key and the authentication type defined by the
tmnxNtpAuthKeyType variable must match.
When the tmnxNtpAuthKeyType is des, the key must be a maximum
of 8 octets. When the tmnxNtpAuthKeyType is messageDigest,
the key may be up to 32 octets long.
When read, tmnxNtpAuthKey always returns an OCTET STRING of
zero length.