Re: Spread-spectrum net (vulnerability of)

RE your item, 

"a sort of virtual-space map, which would reveal
nothing about actual phyical location of the sites or the person you are
contacting."

I'm not so sure... in cellular systems, cells must know where the handsets
are located in order to send incoming calls.  Your transmitter has a
physical location which could presumably be tracked in the normal manner,
and I would expect the overall routing information in a net to be
susceptible to traffic analysis in any case.  An individual who is using the
system to communicate wouldn't be able to find the physical address of
another user, but e.g. an intelligence agency which was looking at the
entire network would.  Even assuming spread-spectrum and various link
encryption techniques on top of whatever end-user encryption is supplied;
with enough traffic and enough time, it should be possible to do TA.  

Or have I missed something....?

-gg

> I'm not so sure... in cellular systems, cells must know where the handsets
> are located in order to send incoming calls.  Your transmitter has a
> physical location which could presumably be tracked in the normal manner,
> and I would expect the overall routing information in a net to be
> susceptible to traffic analysis in any case.  An individual who is using the
> system to communicate wouldn't be able to find the physical address of
> another user, but e.g. an intelligence agency which was looking at the
> entire network would.  Even assuming spread-spectrum and various link
> encryption techniques on top of whatever end-user encryption is supplied;
> with enough traffic and enough time, it should be possible to do TA.  

Cell systems have to know which cell you're in (visualize each cell as
a circle centered on the cell site) to know how to route a call _to_
you. I believe the MTSO (== cellular CO) will route the call directly
to the cell site for the cell you're in.

Of course, the cell will also know what cell you're in when you
originate a call. This knowledge is useful for traffic analysis, but
it's also required for the system to be able to route incoming and
outgoing calls.

An alternative is the ham packet radio-style addressing of
user@node@node..., where "user" represents the call sign of the
intended receiver and each node represents the call of a digipeater
between the sender and recipient. The hard part here is that you must
be able to dynamically generate a route between Alice and Bob if
either of them move from their last known location.

Of course, there's always store-and-forward. A spread-spectrum network
of small digipeaters, combined with crypto remailing and pool
software, would really be something. I'm not sure that it would work
well for spread-spectrum SLIP, though.

-Paul

-- 
Paul Robichaux, KD4JZG     | "Change the world for a better tomorrow. But
perobich@ingr.com          |  watch your ass today." - aaron@halcyon.com
Intergraph Federal Systems | Be a cryptography user- ask me how.

> "a sort of virtual-space map, which would reveal
> nothing about actual phyical location of the sites
> or the person you are contacting."
>
> I'm not so sure... in cellular systems, cells must know where the handsets
> are located in order to send incoming calls.  Your transmitter has a
> physical location which could presumably be tracked in the normal manner,
> and I would expect the overall routing information in a net to be
> susceptible to traffic analysis in any case.  An individual who is using the
> system to communicate wouldn't be able to find the physical address of
> another user, but e.g. an intelligence agency which was looking at the
> entire network would.

You've hit the key concept - motion.  If you are operating from a fixed
transmitter, finding locations is very difficult.  The problem is that
if someone was to drive around the city in a radio equipped truck, and
log into lots of different nodes, they could at least get a partial map
of where various nodes are located.  This could be countered by
additional software which would emulate the node you logged in on even
tho it actually switched you to another node (you communicate with a
virtual fixed node which may or may not be the actual one you are
communicating with).  hmm...  Which leaves us with the problem of
developing software to do that, and developing some method of logging
into the system which would not be node-specific (if you had to do
something special for each node, it would immediately reveal what areas
the nodes were in.)  That creates the problem of developing something
that is not a plainly obvious "log-in" signal that the FCC could look
for.  Ideas?