Sealing wax & eKeyboard

[Sunder]

On Wed, 16 Jul 2003, Tyler Durden wrote:

> "Anything displayed on your screen is visible to the guy across the street
> with a TEMPEST detector unless you work in a Faraday cage. "
> 
> No, no you have the whole thing wrong. As May recently stated, "crypto is 
> economics". 

Well, ok, it "all depends on your security model" is certainly the 1st
factor to consider with how much you're willing to spend on it being a
constraint to that.

If your threat model is simply to have generic good security incase
someone steals your machine, then so long as all your files are encrypted,
the theif just gets whatever the hardware is worth at "it fell of a
truck" prices, and no more.

If your threat model is the fully armed and armorded ninja attack at
3:00am -- which was what I gathered was what Sampo's originally presented
question, then you can assume your attacker would have enough resources to
pull off a TEMPEST van across the street, etc.

So do you want crypto to keep a rogue government out of your fiels, or
keep your kid sister from reading your email? etc...

An on screen virtual keyboard is much easier to see than a real keyboard
even by a shitty pinhole camera.  A real keyboard would have to be viewed
from above, otherwise, all you can do is infer the keystrokes - which
gives you a hint of what they are for a passphrase, but not much else.  
On screen keyboard can be seen much easier and your mouse pointer gives
you away.

So it all depends on who "they" is.  Either way, if "they" believe you are
a nice jucy target, and their chances to net lots of data off your machine
are high, they will park the TEMPEST SUV outside your door.  Not much
question of that...

If "they" are watching everyone for patterns and you don't stick out like
a sore thumb, there's not much need for any of the above.

> Empire State building, I'll probably work harder to hide it. If I'm sharing 
> mp3's on Kazaa or whatever and I don't want to have RIAA make an example out 
> of me, that virtual keyboard may be just right.

No, virtual keyboard won't save your ass.  Your ISP will had it over on a
plate along with trimmings (traffic logs, etc.)  If you're sharing MP3's
on Kazaa, you're easy to find, and logs are proof enough.  All the RIAA
troll has to do is download one song off your IP, prove it came from
your IP, and get the ISP to give them logs, and you're toast.  Doesn't
matter that your hard drive has since been wiped or encrypted or is
unreadable.

Using crypto to protect files you have already shared with the public is
neurotic as a security measure.

> The real danger of crypto and, I'd argue, a virtual keyboard in this case, 
> is that by spending tiny fractions of money we can make it prohibitively 
> costly for "them" to monitor a large number of transactions. 

And if you do and are noticed, "they" will spend that money because you
will be an obvious and clear target.  If they can get away with "why don't
you just show us what you have - what do you have something to hide?" line
to cow sheeple into giving them access, in their mind, you'd be the one to
make their careers.

> Forget 
> unbreakability. Forget Faraday cages (you don't have anything that important 
> to hide anyway). Cheap, easy and scalable is the only way to bumrush this 
> show.

Again, what's your threat model, who is your attacker, how much are you
willing to spend on it?


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