[E-Lang] Irreversible delegation, was: draft statement of co n sensus

Karp, Alan alan_karp@hp.com
Fri, 9 Feb 2001 08:59:49 -0800

> -----Original Message-----
> From: Ralph Hartley [mailto:hartley@aic.nrl.navy.mil]
> Sent: Friday, February 09, 2001 6:34 AM
> To: Karp, Alan
> Cc: E Language Discussions
> Subject: Re: [E-Lang] Irreversible delegation, was: draft statement of
> con sensus

As you can see, I'm fumbling around here with an idea that may or may not
lead anywhere.  I brought up rights amplification because the discussion to
this point has concerned a single power.  I'm hoping that discussing a
slightly more complex case will lead to some insight.

> Karp, Alan wrote:
> > Note that Mallet and Carol have no need to invite Bob to 
> the banquet.
> > Bob can't revoke the privilege he gave to Mallet, so he has 
> no recourse.
> > If there is no honor among thieves, then Bob won't give 
> Mallet the right
> > to the can.  Why should Mallet get all the goodies?  (I'm 
> assuming no
> > side payments.  Is that fair?)
> No. When you irrevocably give something it is customary to receive 
> something in return, that's called a sale.

Of course.  In my view that weakens the meaning of "prevent", perhaps beyond
recognition.  However, if all Mallet has or can get that Bob might want is
the tuna, then we have something to talk about.  

> >   Alice's tuna is protected because the
> > only way that Bob can give Mallet what he needs to get the 
> tuna is to do
> > so irrevocably.
> You are also assuming that Bob is an "ideal economic agent", 
> that he has 
> a self interest, and always acts in that interest. One of the 
> real life 
> examples where people are prevented from taking irrevocable 
> actions is 
> to protect children from their own foolishness (in many jurisdictions 
> children cannot make legally binding contracts for this reason).

True, but aren't there examples of such behavior.  I've used the word
"prevent" in the weak sense of not being able to gain by doing it.  That's
much weaker than being unable to do it under any circumstances.  Maybe
someone can see how to turn a weak "prevent" into a strong one.  On the
other hand, this won't be the first time I've gone down a dead end.

> > Is this reasonable?  Can anyone see how to turn the story 
> around so Bob
> > only benefits from irrevocable delegation?
> A power that MUST be irrevocably delegated to be effective?
> Alice want's to give something to an agent chosen by bob but 
> want's to 
> prevent Bob from getting it, even if the agent conspires with Bob.

Well, except for the conspire part which is circumvented by the message
laundry, there is a way.   Bob introduces Mallet to Alice, and Alice gives
the power directly to Mallet.  How could Alice possibly benefit?  Well,
maybe Bob doesn't have a valid credit card, but Mallet does.  (I'm assuming
Alice wants to charge the presenter of the capability, not the person it was
issued to.) 

What's to prevent Mallet from giving the power to Bob?  Nothing with
standard capabilities, but e-speak Beta 2.2 handled this quite naturally.
Since all that was given out was a name bound to the capability, and all
names in e-speak Beta 2.2 were path based, the capability Alice gives
directly to Mallet has meaning only if presented by Mallet.  We can't even
express Bob's presenting Mallet's capability directly to Alice.  (To be more
precise, I should say that the capability only has meaning if it is
presented to Alice's machine by Mallet's machine.  All users on another
machine are logically equivalent as far as Alice's machine is concerned.
Any identification of users on another machine implies a certain, not
totally unreasonable, trust of the integrity of the other machine.)

> Without more, I don't see how it is possible, and even *I* 
> have trouble 
> thinking of a practical example of that one.

I don't see it either.

> I would have to think about it.
> Ralph Hartley
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Alan Karp
Principal Scientist
Decision Technology Department
Hewlett-Packard Laboratories MS 1U-2
1501 Page Mill Road
Palo Alto, CA 94304
(650) 857-3967, fax (650) 857-6278