[Dshield] OT BPL

Johannes B. Ullrich jullrich at euclidian.com
Thu Oct 20 20:39:32 GMT 2005

>  I've been reading about BPL.  A lot of concerns about RF regarding
> interference with HAM operators and other RF devices.  One question that
> I can't seam to find an answer to is how secure is the system?  If a HAM
> operator can jamb the BPL just by getting on the right freq., why can't
> someone sniff the network on the same freq.?  BPL is starting to gain
> momentum and looks promising.  Looks like another access point we'll all
> need to start thinking about.

BPL (Broadband over Power Lines I assume ;-) ) has indeed been gaining
some speed. I think a lot of the security aspects haven't fully been
worked out yet. But well, why not deploy it first ;-).

One important consideration is that the signal will not pass across a
transformer. However, there are devices to "bridge" them. This means
however, that all users connected to one transformer are essentially on
a LAN. You should be able to sniff each others traffic.

How many households are on a transformer? Not many in the US (110 V
technology). You can assume that you have one transformer for about 10
or so houses. You usually see them mounted to the poles out on the
street. In Europe, this is different. The 240V technology employed in
Europe allows for a few hundred households to be connected to the same
transformer (the higher the voltage, the less losses per distance and
the longer the line to the transformer).

Now based on these limits, there are two different architectures. In
Europe (many houses per transformer), you may see a T1 going up to a
transformer and used as an uplink for the customers connected to the
transformer. In the US on the other hand, BPL is discussed for
long-distance connections, and the "last 100 yards" would be implemented
with WIFI which may be cheaper then installing the transformer bridges.

The interference issues are an issue for high voltage lines, and less
for lower voltage lines. You probably need some special equipment to
pickup the signal, but no idea how complex such equipment would be. But
essentially, if you modulate a high frequency signal on a high voltage
line, you got a pretty good radio.

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