Echelon i.LON 600 LonWorks/IP Server - Manual (Page 64)

Section 2: Advanced Topics
MD5 Authentication
MD5 authentication is a channel-wide property that uses an authentication key to set
security on a L
ON W ORKS /IP channel. The authentication key is used to calculate the
MD5 digest. When authentication is enabled and the i.LON 600 prepares to send an IP
packet, the i.LON 600 uses the authentication key and the public MD5 algorithm to
compute a digest over each L
ON W ORKS packet in the UDP payload. For standard
channels, the APDU is identical to the packets described in the EIA-852 protocol
standard for sending L
ON W ORKS packets over IP. The computed digest is appended to
the end of the APDU and the packet is sent over the network. Authentication digests are
appended to both L
ON W ORKS data packets and Configuration Server control packets.
One or more i.LON 600 devices receive the packet and use their authentication key to
compute a digest over the same payload (not including the appended digest). The
receiving i.LON 600 compares the digest it computed to the one that was sent in the
packet. If the digests match, the packet is authentic. If the digests do not match, the
packet is considered to have been corrupted, tampered with, or otherwise unacceptable,
and is discarded. The digest includes the entire packet, which contains a time stamp for
preventing replay attacks when used in conjunction with a configured channel timeout
value. For more information on the MD5 algorithm refer to RFC 1321.
The authentication key, consisting of 16 HEX pairs, is set for each i.LON 600 through the
Console Application or Web page. Authentication is enabled and the authentication key
set for the L
ON W ORKS /IP channel through the Configuration Server. To reset a lost
authentication key, you must obtain physical access to the device and reset the key
through the device’s serial port or use the setup Web page.
56 L ON W ORKS /IP Channel Parameters