Need help securing RF telemetry

I am developing a small scale SCADA system for a client who needs
to secure RF signals between base units and RTU's. He uses
frequency-shifting RF transceivers, but physical security for
the RTU's can't be guaranteed, and an attacker stealing one would
have access to the encrypted traffic.

I'm programming the micro on the RTU, an MSP430F2121 (4k bytes
code, 256 bytes RAM). There's not much room to implement a standard
algorithm such as SHA-1 or XTEA. What's the best I can hope to do
with such a tiny processor? He may be convinced to use the F2131
(with 8k code space) but above that per unit cost gets to be an issue.
Any help appreciated,

Sean_Q_
ps. The world's first(?) cyber attack on a community's infrastructure
through RF telemetry was an inside job:
http://ddanchev.blogspot.com/2006/10/scada-security-incidents-and-critical.html
http://www.theage.com.au/articles/2003/06/21/1056119529509.html
http://www.mail-archive.com/cybercrime-alerts@xxxxxxxxxx/msg00577.html
.

Quantcast