From: jpc@tauon.ph.unimelb.edu.au (John Costella)
Subject: Re: TECH: Worlds, rooms & portals
Date: Mon, 10 May 93 4:29:41 EET



> |> > This is an interesting possibility - perhaps it will be a bit too
> |> > complicated to implement within the current structure, but I do
> |> > like the concept of going up to a virtual machine (like an ATM)
> |> > and punching in the password to enter the room behind! :-)
> |>
> |> Ah no this only works in the real world---the virtual world is far
> |> too flexible for such lax security. A virtuhacker could easily
> |> shrink himself to the size of a mosquito and then hide in the corner
> |> of the keypad and watch you entering your password.
> |>
> |> :-)
> 
> You're right John! This is obvious now you point it out! :-) What a problem!
> 
> You're probably going to have to "plug in" to the VATM (Virtual ATM) so that
> it can do a ID verification, background check, SSN comparison with your
> Mother's maiden name! :-)
> 
> Looks like this is whole new area for the lawyers :-(

Yeah, this problem of security is going to have some non-trivial
ramifications. The simplest answer to my mozzie argument is to have a
sign outside the *previous* door saying ``No Mosquitoes Allowed''.
Apart from the fact that, as it stands now, this sign would probably
contravene Anti-Discrimination legislation (``... on the basis of race
or physical appearance ... '' ;-), it also gives you `global
prohibition conditions', like the Dirac magnetic monopole argument,
that are far from intuitive. (Dirac pointed out that the existence of
ONE magnetic monopole ANYWHERE in the universe would mean that
electric charge would have to be quantised.)

One way around things is to have the shared world look substantially
different to the different people that are sharing it---not in terms
of resolution etc., but in terms of the bare essentials. This might
get messy, but you can do it. You could isolate this non-shared nature
to specific areas, and make the `isolation' 100% in those areas and 0%
everywhere else, so as to avoid the logistics of catering for every
pathological combination of events. For example, go back to the
virtual ATM. You can't just hide the keypad, because the person's
fingers will show the number. You can't hide their fingers, since when
do you decide to hide them? And what if they are carrying a can of
Coke when their fingers disappear---does the Coke disappear too? It's
a programmer's nightmare.

A workable general solution is to have the electronic equivalent of
safety deposit box access areas. You have little closets or access
foyers, each labelled `secure area'. Inside that closet or access
foyer, you have a `virtual machine' (in the original IBM sense of the
word `virtual') for each world participant. (I.e., it is like a
virtual DOS box under OS/2 or Windows, if you are of later vintage.)
What this means is that, as you walk into one of these secured areas,
you see yourself and all the equipment inside; but everyone ELSE in
the virtual world sees you *disappear* as you enter that room (since
you are entering your virtual machine, not theirs; hence, theirs stays
empty).  You can then enter your password in safety, because the only
people inside that box are you and the operating system. It is a
`black hole' as far as you are concerned: nothing inside gets out.

Even though a 100% public / 100% private division of the virtuopolis
like that described above is the simplest, there are some mind-
boggling problems in designing the physics of even such a simple
world. You want your security area to be a black hole. That presumedly
means you don't want SOUND to get out either---since what happens if
the participant, feeling secure in their private box, mumbles the
password as they enter it?---or if you have a voiceprint or vocal
querying procedure? Since the world is virtual, someone could
arbitrarily amplify *any* mumbled sound---even a distorted one, if
they have taken the time to measure the transfer functions of the room
in question (which, being virtual, requires only virtually instruments
:-).  You also want the room to be soundproof the other way, so that
outside noise does not distract you. But on the other hand, there's no
reason not to let the *images* from the public area come through the
window. So you have to set up the physics of your sound and graphics
to cater for all this, with `local' and `global' photons (if you one
day get to the luxury of ray-tracing), and so on. Then you need to
take care to absorb the sound and photons at the walls rather than
reflecting them, otherwise they will build up until you are deafened
and blinded! But then the walls will be perfect absorbers---and the
room will be black-body and anechoic, and you'll fall over sick on the
virtual ground.

OK, you don't have quite so many subtleties with today's polygon-based
worlds, but you get the idea. :-) One day you'll need to do a separate
course in Virtual Physics---real Physics won't be sufficient. ;-)

John

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John P. Costella              School of Physics, The University of Melbourne
jpc@tauon.ph.unimelb.edu.au          Tel: +61 3543-7795;  Fax: +61 3347-4783
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