Re: [MUD-Dev] distributed objects

[Kevin Littlejohn <darius#connect,com.au>]

>>> "Laurent Bossavit" wrote
> Kevin Littlejohn sez:
> 
> > Phil's comment on that was that it's impossible to construct a
> > decent fight system, for instance, under that setup, because you
> > can never guarantee that 
> 
> Um... Unless I'm missing a perfectly obvious point (which wouldn't be 
> the first time) don't the solutions outlined at www.erights.org for 
> implementing secure "purses" also fit the bill for combat systems ?  

For anyone who hasn't read it:
http://www.erights.org/elib/capability/ode/ode-capabilities.html#simple-money

Neat system.

There's still reliance on a bunch of things, that may not be immediately
evident, though, to achieve this security.  One of them that doesn't apply
in Moebius (nor, I believe, in any distributed architecture, where the 'bad
guys' have total control over the objects) is a certain non-mutability of
objects.  When you've instantiated an object in E, you can't go back and
change it's methods - what they bind to, what their source code is, etc.
If you could do that, you'd instantiate a purse, then change it's decrement
method.  Presto - you can hand out a decrement that's sealed by the right
thing, works fine, and does exactly what you want - purse of holding,
anyone? ;)

Ok, so the sealer performs some security checks on the method.  In a
distributed world, those security checks are going to be _extremely_
interesting - and valid only until the checks stop being performed (at
which time, the holder of the object will switch methods on you).

End result - you drag more and more stuff back to the server for
verification, until you end up driving the objects data and methods on the
server from a remote point.

Caveat:  I may be wrong, but I can't see where...  As EQ and others have
demonstrated, people will quite happpily step "out of band" to break these
systems - I thought replacing the tiles with transparent ones was good, but
staggering lag on packets back to the server boggles me.

KevinL



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